disk_observer

Declared in "libtorrent/disk_observer.hpp"

struct disk_observer
{
   virtual void on_disk () = 0;
};

virtual void on_disk () = 0;

buffer_allocator_interface

Declared in "libtorrent/disk_buffer_holder.hpp"

the interface for freeing disk buffers, used by the disk_buffer_holder. when implementing disk_interface, this must also be implemented in order to return disk buffers back to libtorrent

struct buffer_allocator_interface
{
   virtual void free_disk_buffer (char* b) = 0;
};

disk_buffer_holder

Declared in "libtorrent/disk_buffer_holder.hpp"

The disk buffer holder acts like a unique_ptr that frees a disk buffer when it's destructed

If this buffer holder is moved-from, default constructed or reset, data() will return nullptr.

struct disk_buffer_holder
{
   disk_buffer_holder& operator= (disk_buffer_holder&&) & noexcept;
   disk_buffer_holder (disk_buffer_holder&&) noexcept;
   disk_buffer_holder (disk_buffer_holder const&) = delete;
   disk_buffer_holder& operator= (disk_buffer_holder const&) = delete;
   disk_buffer_holder (buffer_allocator_interface& alloc
      , char* buf, int sz) noexcept;
   disk_buffer_holder () noexcept = default;
   ~disk_buffer_holder ();
   char* data () const noexcept;
   void reset ();
   void swap (disk_buffer_holder& h) noexcept;
   bool is_mutable () const noexcept;
   explicit operator bool () const noexcept;
   std::ptrdiff_t size () const;
};

disk_buffer_holder (buffer_allocator_interface& alloc
      , char* buf, int sz) noexcept;

disk_buffer_holder () noexcept = default;

~disk_buffer_holder ();

char* data () const noexcept;

void reset ();

void swap (disk_buffer_holder& h) noexcept;

bool is_mutable () const noexcept;

explicit operator bool () const noexcept;

settings_interface

Declared in "libtorrent/settings_pack.hpp"

the common interface to settings_pack and the internal representation of settings.

struct settings_interface
{
   virtual void set_str (int name, std::string val) = 0;
   virtual bool has_val (int name) const = 0;
   virtual void set_bool (int name, bool val) = 0;
   virtual void set_int (int name, int val) = 0;
   virtual std::string const& get_str (int name) const = 0;
   virtual int get_int (int name) const = 0;
   virtual bool get_bool (int name) const = 0;
};

open_file_state

Declared in "libtorrent/disk_interface.hpp"

this contains information about a file that's currently open by the libtorrent disk I/O subsystem. It's associated with a single torrent.

struct open_file_state
{
   file_index_t file_index;
   file_open_mode_t open_mode;
   time_point last_use;
};

file_index

the index of the file this entry refers to into the file_storage file list of this torrent. This starts indexing at 0.

open_mode

open_mode is a bitmask of the file flags this file is currently opened with. For possible flags, see file_open_mode_t.

Note that the read/write mode is not a bitmask. The two least significant bits are used to represent the read/write mode. Those bits can be masked out using the rw_mask constant.

last_use

a (high precision) timestamp of when the file was last used.

disk_interface

Declared in "libtorrent/disk_interface.hpp"

The disk_interface is the customization point for disk I/O in libtorrent. implement this interface and provide a factory function to the session constructor use custom disk I/O. All functions on the disk subsystem (implementing disk_interface) are called from within libtorrent's network thread. For disk I/O to be performed in a separate thread, the disk subsystem has to manage that itself.

Although the functions are called async_*, they do not technically have to be asynchronous, but they support being asynchronous, by expecting the result passed back into a callback. The callbacks must be posted back onto the network thread via the io_context object passed into the constructor. The callbacks will be run in the network thread.

struct disk_interface
{
   virtual storage_holder new_torrent (storage_params const& p
      , std::shared_ptr<void> const& torrent) = 0;
   virtual void remove_torrent (storage_index_t) = 0;
   virtual bool async_write (storage_index_t storage, peer_request const& r
      , char const* buf, std::shared_ptr<disk_observer> o
      , std::function<void(storage_error const&)> handler
      , disk_job_flags_t flags = {}) = 0;
   virtual void async_read (storage_index_t storage, peer_request const& r
      , std::function<void(disk_buffer_holder, storage_error const&)> handler
      , disk_job_flags_t flags = {}) = 0;
   virtual void async_hash (storage_index_t storage, piece_index_t piece, span<sha256_hash> v2
      , disk_job_flags_t flags
      , std::function<void(piece_index_t, sha1_hash const&, storage_error const&)> handler) = 0;
   virtual void async_hash2 (storage_index_t storage, piece_index_t piece, int offset, disk_job_flags_t flags
      , std::function<void(piece_index_t, sha256_hash const&, storage_error const&)> handler) = 0;
   virtual void async_move_storage (storage_index_t storage, std::string p, move_flags_t flags
      , std::function<void(status_t, std::string const&, storage_error const&)> handler) = 0;
   virtual void async_release_files (storage_index_t storage
      , std::function<void()> handler = std::function<void()>()) = 0;
   virtual void async_check_files (storage_index_t storage
      , add_torrent_params const* resume_data
      , aux::vector<std::string, file_index_t> links
      , std::function<void(status_t, storage_error const&)> handler) = 0;
   virtual void async_stop_torrent (storage_index_t storage
      , std::function<void()> handler = std::function<void()>()) = 0;
   virtual void async_rename_file (storage_index_t storage
      , file_index_t index, std::string name
      , std::function<void(std::string const&, file_index_t, storage_error const&)> handler) = 0;
   virtual void async_delete_files (storage_index_t storage, remove_flags_t options
      , std::function<void(storage_error const&)> handler) = 0;
   virtual void async_set_file_priority (storage_index_t storage
      , aux::vector<download_priority_t, file_index_t> prio
      , std::function<void(storage_error const&
      , aux::vector<download_priority_t, file_index_t>)> handler) = 0;
   virtual void async_clear_piece (storage_index_t storage, piece_index_t index
      , std::function<void(piece_index_t)> handler) = 0;
   virtual void update_stats_counters (counters& c) const = 0;
   virtual std::vector<open_file_state> get_status (storage_index_t) const = 0;
   virtual void abort (bool wait) = 0;
   virtual void submit_jobs () = 0;
   virtual void settings_updated () = 0;

   static constexpr disk_job_flags_t force_copy  = 0_bit;
   static constexpr disk_job_flags_t sequential_access  = 3_bit;
   static constexpr disk_job_flags_t volatile_read  = 4_bit;
   static constexpr disk_job_flags_t v1_hash  = 5_bit;
   static constexpr disk_job_flags_t flush_piece  = 7_bit;
};

virtual storage_holder new_torrent (storage_params const& p
      , std::shared_ptr<void> const& torrent) = 0;

virtual void remove_torrent (storage_index_t) = 0;

virtual bool async_write (storage_index_t storage, peer_request const& r
      , char const* buf, std::shared_ptr<disk_observer> o
      , std::function<void(storage_error const&)> handler
      , disk_job_flags_t flags = {}) = 0;
virtual void async_read (storage_index_t storage, peer_request const& r
      , std::function<void(disk_buffer_holder, storage_error const&)> handler
      , disk_job_flags_t flags = {}) = 0;

virtual void async_hash (storage_index_t storage, piece_index_t piece, span<sha256_hash> v2
      , disk_job_flags_t flags
      , std::function<void(piece_index_t, sha1_hash const&, storage_error const&)> handler) = 0;

virtual void async_hash2 (storage_index_t storage, piece_index_t piece, int offset, disk_job_flags_t flags
      , std::function<void(piece_index_t, sha256_hash const&, storage_error const&)> handler) = 0;

virtual void async_move_storage (storage_index_t storage, std::string p, move_flags_t flags
      , std::function<void(status_t, std::string const&, storage_error const&)> handler) = 0;

virtual void async_release_files (storage_index_t storage
      , std::function<void()> handler = std::function<void()>()) = 0;

virtual void async_check_files (storage_index_t storage
      , add_torrent_params const* resume_data
      , aux::vector<std::string, file_index_t> links
      , std::function<void(status_t, storage_error const&)> handler) = 0;

virtual void async_stop_torrent (storage_index_t storage
      , std::function<void()> handler = std::function<void()>()) = 0;

virtual void async_rename_file (storage_index_t storage
      , file_index_t index, std::string name
      , std::function<void(std::string const&, file_index_t, storage_error const&)> handler) = 0;

virtual void async_delete_files (storage_index_t storage, remove_flags_t options
      , std::function<void(storage_error const&)> handler) = 0;

virtual void async_set_file_priority (storage_index_t storage
      , aux::vector<download_priority_t, file_index_t> prio
      , std::function<void(storage_error const&
      , aux::vector<download_priority_t, file_index_t>)> handler) = 0;

virtual void async_clear_piece (storage_index_t storage, piece_index_t index
      , std::function<void(piece_index_t)> handler) = 0;

virtual void update_stats_counters (counters& c) const = 0;

virtual std::vector<open_file_state> get_status (storage_index_t) const = 0;

virtual void abort (bool wait) = 0;

virtual void submit_jobs () = 0;

virtual void settings_updated () = 0;

storage_holder

Declared in "libtorrent/disk_interface.hpp"

a unique, owning, reference to the storage of a torrent in a disk io subsystem (class that implements disk_interface). This is held by the internal libtorrent torrent object to tie the storage object allocated for a torrent to the lifetime of the internal torrent object. When a torrent is removed from the session, this holder is destructed and will inform the disk object.

struct storage_holder
{
   storage_holder (storage_index_t idx, disk_interface& disk_io);
   ~storage_holder ();
   storage_holder () = default;
   explicit operator bool () const;
   operator storage_index_t () const;
   void reset ();
   storage_holder& operator= (storage_holder const&) = delete;
   storage_holder (storage_holder const&) = delete;
   storage_holder (storage_holder&& rhs) noexcept;
   storage_holder& operator= (storage_holder&& rhs) noexcept;
};

file_open_mode_t

Declared in "libtorrent/disk_interface.hpp"

read_only

open the file for reading only

write_only

open the file for writing only

read_write

open the file for reading and writing

rw_mask

the mask for the bits determining read or write mode

sparse

open the file in sparse mode (if supported by the filesystem).

no_atime

don't update the access timestamps on the file (if supported by the operating system and filesystem). this generally improves disk performance.

random_access

When this is not set, the kernel is hinted that access to this file will be made sequentially.

mmapped

the file is memory mapped

The pop_alerts() function on session is the main interface for retrieving alerts (warnings, messages and errors from libtorrent). If no alerts have been posted by libtorrent pop_alerts() will return an empty list.

By default, only errors are reported. settings_pack::alert_mask can be used to specify which kinds of events should be reported. The alert mask is a combination of the alert_category_t flags in the alert class.

Every alert belongs to one or more category. There is a cost associated with posting alerts. Only alerts that belong to an enabled category are posted. Setting the alert bitmask to 0 will disable all alerts (except those that are non-discardable). Alerts that are responses to API calls such as save_resume_data() and post_session_stats() are non-discardable and will be posted even if their category is disabled.

There are other alert base classes that some alerts derive from, all the alerts that are generated for a specific torrent are derived from torrent_alert, and tracker events derive from tracker_alert.

Alerts returned by pop_alerts() are only valid until the next call to pop_alerts(). You may not copy an alert object to access it after the next call to pop_alerts(). Internal members of alerts also become invalid once pop_alerts() is called again.

dht_routing_bucket

Declared in "libtorrent/alert_types.hpp"

struct to hold information about a single DHT routing table bucket

struct dht_routing_bucket
{
   int num_nodes;
   int num_replacements;
   int last_active;
};

num_nodes num_replacements

the total number of nodes and replacement nodes in the routing table

last_active

number of seconds since last activity

torrent_alert

Declared in "libtorrent/alert_types.hpp"

This is a base class for alerts that are associated with a specific torrent. It contains a handle to the torrent.

Note that by the time the client receives a torrent_alert, its handle member may be invalid.

struct torrent_alert : alert
{
   std::string message () const override;
   char const* torrent_name () const;

   torrent_handle handle;
};

std::string message () const override;

peer_alert

Declared in "libtorrent/alert_types.hpp"

The peer alert is a base class for alerts that refer to a specific peer. It includes all the information to identify the peer. i.e. ip and peer-id.

struct peer_alert : torrent_alert
{
   std::string message () const override;

   aux::noexcept_movable<tcp::endpoint> endpoint;
   peer_id pid;
};

endpoint

The peer's IP address and port.

pid

the peer ID, if known.

tracker_alert

Declared in "libtorrent/alert_types.hpp"

This is a base class used for alerts that are associated with a specific tracker. It derives from torrent_alert since a tracker is also associated with a specific torrent.

struct tracker_alert : torrent_alert
{
   std::string message () const override;
   char const* tracker_url () const;

   aux::noexcept_movable<tcp::endpoint> local_endpoint;
};

char const* tracker_url () const;

torrent_removed_alert

Declared in "libtorrent/alert_types.hpp"

The torrent_removed_alert is posted whenever a torrent is removed. Since the torrent handle in its base class will usually be invalid (since the torrent is already removed) it has the info hash as a member, to identify it. It's posted when the alert_category::status bit is set in the alert_mask.

Note that the handle remains valid for some time after torrent_removed_alert is posted, as long as some internal libtorrent task (such as an I/O task) refers to it. Additionally, other alerts like save_resume_data_alert may be posted after torrent_removed_alert. To synchronize on whether the torrent has been removed or not, call torrent_handle::in_session(). This will return true before torrent_removed_alert is posted, and false afterward.

Even though the handle member doesn't point to an existing torrent anymore, it is still useful for comparing to other handles, which may also no longer point to existing torrents, but to the same non-existing torrents.

The torrent_handle acts as a weak_ptr, even though its object no longer exists, it can still compare equal to another weak pointer which points to the same non-existent object.

struct torrent_removed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   info_hash_t info_hashes;
   client_data_t userdata;
};

userdata

'userdata` as set in add_torrent_params at torrent creation. This can be used to associate this torrent with related data in the client application more efficiently than info_hashes.

read_piece_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when the asynchronous read operation initiated by a call to torrent_handle::read_piece() is completed. If the read failed, the torrent is paused and an error state is set and the buffer member of the alert is 0. If successful, buffer points to a buffer containing all the data of the piece. piece is the piece index that was read. size is the number of bytes that was read.

If the operation fails, error will indicate what went wrong.

struct read_piece_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage;
   error_code const error;
   boost::shared_array<char> const buffer;
   piece_index_t const piece;
   int const size;
};

file_completed_alert

Declared in "libtorrent/alert_types.hpp"

This is posted whenever an individual file completes its download. i.e. All pieces overlapping this file have passed their hash check.

struct file_completed_alert final : torrent_alert
{
   std::string message () const override;

   file_index_t const index;
};

index

refers to the index of the file that completed.

file_renamed_alert

Declared in "libtorrent/alert_types.hpp"

This is posted as a response to a torrent_handle::rename_file() call, if the rename operation succeeds.

struct file_renamed_alert final : torrent_alert
{
   std::string message () const override;
   char const* new_name () const;
   char const* old_name () const;

   static constexpr alert_category_t static_category  = alert_category::storage;
   file_index_t const index;
};

char const* new_name () const;
char const* old_name () const;

file_rename_failed_alert

Declared in "libtorrent/alert_types.hpp"

This is posted as a response to a torrent_handle::rename_file() call, if the rename operation failed.

struct file_rename_failed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage;
   file_index_t const index;
   error_code const error;
};

index error

refers to the index of the file that was supposed to be renamed, error is the error code returned from the filesystem.

performance_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a limit is reached that might have a negative impact on upload or download rate performance.

struct performance_alert final : torrent_alert
{
   std::string message () const override;

   enum performance_warning_t
   {
      outstanding_disk_buffer_limit_reached,
      outstanding_request_limit_reached,
      upload_limit_too_low,
      download_limit_too_low,
      send_buffer_watermark_too_low,
      too_many_optimistic_unchoke_slots,
      too_high_disk_queue_limit,
      aio_limit_reached,
      deprecated_bittyrant_with_no_uplimit,
      too_few_outgoing_ports,
      too_few_file_descriptors,
      num_warnings,
   };

   static constexpr alert_category_t static_category  = alert_category::performance_warning;
   performance_warning_t const warning_code;
};

min(512, max(upload_rate * send_buffer_watermark_factor / 100, send_buffer_watermark))

state_changed_alert

Declared in "libtorrent/alert_types.hpp"

Generated whenever a torrent changes its state.

struct state_changed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   torrent_status::state_t const state;
   torrent_status::state_t const prev_state;
};

state

the new state of the torrent.

prev_state

the previous state.

tracker_error_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated on tracker time outs, premature disconnects, invalid response or a HTTP response other than "200 OK". From the alert you can get the handle to the torrent the tracker belongs to.

struct tracker_error_alert final : tracker_alert
{
   std::string message () const override;
   char const* failure_reason () const;

   static constexpr alert_category_t static_category  = alert_category::tracker | alert_category::error;
   int const times_in_row;
   error_code const error;
   operation_t op;
   protocol_version version;
};

char const* failure_reason () const;

tracker_warning_alert

Declared in "libtorrent/alert_types.hpp"

This alert is triggered if the tracker reply contains a warning field. Usually this means that the tracker announce was successful, but the tracker has a message to the client.

struct tracker_warning_alert final : tracker_alert
{
   std::string message () const override;
   char const* warning_message () const;

   static constexpr alert_category_t static_category  = alert_category::tracker | alert_category::error;
   protocol_version version;
};

char const* warning_message () const;

scrape_reply_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a scrape request succeeds.

struct scrape_reply_alert final : tracker_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::tracker;
   int const incomplete;
   int const complete;
   protocol_version version;
};

incomplete complete

the data returned in the scrape response. These numbers may be -1 if the response was malformed.

version

the bittorrent protocol version that was scraped

scrape_failed_alert

Declared in "libtorrent/alert_types.hpp"

If a scrape request fails, this alert is generated. This might be due to the tracker timing out, refusing connection or returning an http response code indicating an error.

struct scrape_failed_alert final : tracker_alert
{
   std::string message () const override;
   char const* error_message () const;

   static constexpr alert_category_t static_category  = alert_category::tracker | alert_category::error;
   error_code const error;
   protocol_version version;
};

char const* error_message () const;

tracker_reply_alert

Declared in "libtorrent/alert_types.hpp"

This alert is only for informational purpose. It is generated when a tracker announce succeeds. It is generated regardless what kind of tracker was used, be it UDP, HTTP or the DHT.

struct tracker_reply_alert final : tracker_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::tracker;
   int const num_peers;
   protocol_version version;
};

num_peers

tells how many peers the tracker returned in this response. This is not expected to be greater than the num_want settings. These are not necessarily all new peers, some of them may already be connected.

version

the bittorrent protocol version that was announced

dht_reply_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated each time the DHT receives peers from a node. num_peers is the number of peers we received in this packet. Typically these packets are received from multiple DHT nodes, and so the alerts are typically generated a few at a time.

struct dht_reply_alert final : tracker_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht | alert_category::tracker;
   int const num_peers;
};

tracker_announce_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated each time a tracker announce is sent (or attempted to be sent). There are no extra data members in this alert. The url can be found in the base class however.

struct tracker_announce_alert final : tracker_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::tracker;
   event_t const event;
   protocol_version version;
};

event

specifies what event was sent to the tracker. See event_t.

version

the bittorrent protocol version that is announced

hash_failed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a finished piece fails its hash check. You can get the handle to the torrent which got the failed piece and the index of the piece itself from the alert.

struct hash_failed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   piece_index_t const piece_index;
};

peer_ban_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a peer is banned because it has sent too many corrupt pieces to us. ip is the endpoint to the peer that was banned.

struct peer_ban_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
};

peer_unsnubbed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a peer is un-snubbed. Essentially when it was snubbed for stalling sending data, and now it started sending data again.

struct peer_unsnubbed_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
};

peer_snubbed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a peer is snubbed, when it stops sending data when we request it.

struct peer_snubbed_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
};

peer_error_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a peer sends invalid data over the peer-peer protocol. The peer will be disconnected, but you get its ip address from the alert, to identify it.

struct peer_error_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
   operation_t op;
   error_code const error;
};

op

a 0-terminated string of the low-level operation that failed, or nullptr if there was no low level disk operation.

error

tells you what error caused this alert.

peer_connect_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted every time an incoming peer connection both successfully passes the protocol handshake and is associated with a torrent, or an outgoing peer connection attempt succeeds. For arbitrary incoming connections, see incoming_connection_alert.

struct peer_connect_alert final : peer_alert
{
   std::string message () const override;

   enum direction_t
   {
      in,
      out,
   };

   static constexpr alert_category_t static_category  = alert_category::connect;
   direction_t direction;
   socket_type_t socket_type;
};

peer_disconnected_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a peer is disconnected for any reason (other than the ones covered by peer_error_alert ).

struct peer_disconnected_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::connect;
   socket_type_t const socket_type;
   operation_t const op;
   error_code const error;
   close_reason_t const reason;
};

socket_type

the kind of socket this peer was connected over

op

the operation or level where the error occurred. Specified as an value from the operation_t enum. Defined in operations.hpp.

error

tells you what error caused peer to disconnect.

reason

the reason the peer disconnected (if specified)

invalid_request_alert

Declared in "libtorrent/alert_types.hpp"

This is a debug alert that is generated by an incoming invalid piece request. ip is the address of the peer and the request is the actual incoming request from the peer. See peer_request for more info.

struct invalid_request_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
   peer_request const request;
   bool const we_have;
   bool const peer_interested;
   bool const withheld;
};

request

the request we received from the peer

we_have

true if we have this piece

peer_interested

true if the peer indicated that it was interested to download before sending the request

withheld

if this is true, the peer is not allowed to download this piece because of super-seeding rules.

torrent_finished_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a torrent switches from being a downloader to a seed. It will only be generated once per torrent. It contains a torrent_handle to the torrent in question.

struct torrent_finished_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
};

piece_finished_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted every time a piece completes downloading and passes the hash check. This alert derives from torrent_alert which contains the torrent_handle to the torrent the piece belongs to. Note that being downloaded and passing the hash check may happen before the piece is also fully flushed to disk. So torrent_handle::have_piece() may still return false

struct piece_finished_alert final : torrent_alert
{
   std::string message () const override;

   piece_index_t const piece_index;
};

piece_index

the index of the piece that finished

request_dropped_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a peer rejects or ignores a piece request.

struct request_dropped_alert final : peer_alert
{
   std::string message () const override;

   int const block_index;
   piece_index_t const piece_index;
};

block_timeout_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a block request times out.

struct block_timeout_alert final : peer_alert
{
   std::string message () const override;

   int const block_index;
   piece_index_t const piece_index;
};

block_finished_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a block request receives a response.

struct block_finished_alert final : peer_alert
{
   std::string message () const override;

   int const block_index;
   piece_index_t const piece_index;
};

block_downloading_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a block request is sent to a peer.

struct block_downloading_alert final : peer_alert
{
   std::string message () const override;

   int const block_index;
   piece_index_t const piece_index;
};

unwanted_block_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a block is received that was not requested or whose request timed out.

struct unwanted_block_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
   int const block_index;
   piece_index_t const piece_index;
};

storage_moved_alert

Declared in "libtorrent/alert_types.hpp"

The storage_moved_alert is generated when all the disk IO has completed and the files have been moved, as an effect of a call to torrent_handle::move_storage. This is useful to synchronize with the actual disk. The storage_path() member return the new path of the storage.

struct storage_moved_alert final : torrent_alert
{
   std::string message () const override;
   char const* old_path () const;
   char const* storage_path () const;

   static constexpr alert_category_t static_category  = alert_category::storage;
};

char const* old_path () const;
char const* storage_path () const;

storage_moved_failed_alert

Declared in "libtorrent/alert_types.hpp"

The storage_moved_failed_alert is generated when an attempt to move the storage, via torrent_handle::move_storage(), fails.

struct storage_moved_failed_alert final : torrent_alert
{
   std::string message () const override;
   char const* file_path () const;

   static constexpr alert_category_t static_category  = alert_category::storage;
   error_code const error;
   operation_t op;
};

char const* file_path () const;

torrent_deleted_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a request to delete the files of a torrent complete.

This alert is posted in the alert_category::storage category, and that bit needs to be set in the alert_mask.

struct torrent_deleted_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage;
   info_hash_t info_hashes;
};

info_hashes

The info-hash of the torrent that was just deleted. Most of the time the torrent_handle in the torrent_alert will be invalid by the time this alert arrives, since the torrent is being deleted. The info_hashes member is hence the main way of identifying which torrent just completed the delete.

torrent_delete_failed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a request to delete the files of a torrent fails. Just removing a torrent from the session cannot fail

struct torrent_delete_failed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage
   | alert_category::error;
   error_code const error;
   info_hash_t info_hashes;
};

error

tells you why it failed.

info_hashes

the info hash of the torrent whose files failed to be deleted

save_resume_data_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated as a response to a torrent_handle::save_resume_data request. It is generated once the disk IO thread is done writing the state for this torrent.

struct save_resume_data_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage;
   add_torrent_params params;
};

params

the params object is populated with the torrent file whose resume data was saved. It is suitable to be:

• added to a session with add_torrent() or async_add_torrent()
• saved to disk with write_resume_data()
• turned into a magnet link with make_magnet_uri()
• saved as a .torrent file with write_torrent_file()

save_resume_data_failed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated instead of save_resume_data_alert if there was an error generating the resume data. error describes what went wrong.

struct save_resume_data_failed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage
   | alert_category::error;
   error_code const error;
};

error

the error code from the resume_data failure

torrent_paused_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated as a response to a torrent_handle::pause request. It is generated once all disk IO is complete and the files in the torrent have been closed. This is useful for synchronizing with the disk.

struct torrent_paused_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
};

torrent_resumed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated as a response to a torrent_handle::resume() request. It is generated when a torrent goes from a paused state to an active state.

struct torrent_resumed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
};

torrent_checked_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when a torrent completes checking. i.e. when it transitions out of the checking files state into a state where it is ready to start downloading

struct torrent_checked_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
};

url_seed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a HTTP seed name lookup fails.

struct url_seed_alert final : torrent_alert
{
   std::string message () const override;
   char const* server_url () const;
   char const* error_message () const;

   static constexpr alert_category_t static_category  = alert_category::peer | alert_category::error;
   error_code const error;
};

char const* server_url () const;

char const* error_message () const;

file_error_alert

Declared in "libtorrent/alert_types.hpp"

If the storage fails to read or write files that it needs access to, this alert is generated and the torrent is paused.

struct file_error_alert final : torrent_alert
{
   std::string message () const override;
   char const* filename () const;

   static constexpr alert_category_t static_category  = alert_category::status
   | alert_category::storage;
   error_code const error;
   operation_t op;
};

char const* filename () const;

metadata_failed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when the metadata has been completely received and the info-hash failed to match it. i.e. the metadata that was received was corrupt. libtorrent will automatically retry to fetch it in this case. This is only relevant when running a torrent-less download, with the metadata extension provided by libtorrent.

struct metadata_failed_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   error_code const error;
};

error

indicates what failed when parsing the metadata. This error is what's returned from lazy_bdecode().

metadata_received_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when the metadata has been completely received and the torrent can start downloading. It is not generated on torrents that are started with metadata, but only those that needs to download it from peers (when utilizing the libtorrent extension).

There are no additional data members in this alert.

Typically, when receiving this alert, you would want to save the torrent file in order to load it back up again when the session is restarted. Here's an example snippet of code to do that:

torrent_handle h = alert->handle;
std::shared_ptr<torrent_info const> ti = h.torrent_file();
create_torrent ct(*ti);
entry te = ct.generate();
std::vector<char> buffer;
bencode(std::back_inserter(buffer), te);
FILE* f = fopen((to_hex(ti->info_hashes().get_best().to_string()) + ".torrent").c_str(), "wb+");
if (f) {
        fwrite(&buffer[0], 1, buffer.size(), f);
        fclose(f);
}

struct metadata_received_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
};

udp_error_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when there is an error on a UDP socket. The UDP sockets are used for all uTP, DHT and UDP tracker traffic. They are global to the session.

struct udp_error_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   aux::noexcept_movable<udp::endpoint> endpoint;
   operation_t operation;
   error_code const error;
};

endpoint

the source address associated with the error (if any)

operation

the operation that failed

error

the error code describing the error

external_ip_alert

Declared in "libtorrent/alert_types.hpp"

Whenever libtorrent learns about the machines external IP, this alert is generated. The external IP address can be acquired from the tracker (if it supports that) or from peers that supports the extension protocol. The address can be accessed through the external_address member.

struct external_ip_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   aux::noexcept_movable<address> external_address;
};

external_address

the IP address that is believed to be our external IP

listen_failed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when none of the ports, given in the port range, to session can be opened for listening. The listen_interface member is the interface that failed, error is the error code describing the failure.

In the case an endpoint was created before generating the alert, it is represented by address and port. The combinations of socket type and operation in which such address and port are not valid are: accept - i2p accept - socks5 enum_if - tcp

libtorrent may sometimes try to listen on port 0, if all other ports failed. Port 0 asks the operating system to pick a port that's free). If that fails you may see a listen_failed_alert with port 0 even if you didn't ask to listen on it.

struct listen_failed_alert final : alert
{
   std::string message () const override;
   char const* listen_interface () const;

   static constexpr alert_category_t static_category  = alert_category::status | alert_category::error;
   error_code const error;
   operation_t op;
   lt::socket_type_t const socket_type;
   aux::noexcept_movable<lt::address> address;
   int const port;
};

char const* listen_interface () const;

listen_succeeded_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when the listen port succeeds to be opened on a particular interface. address and port is the endpoint that successfully was opened for listening.

struct listen_succeeded_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   aux::noexcept_movable<lt::address> address;
   int const port;
   lt::socket_type_t const socket_type;
};

address

the address libtorrent ended up listening on. This address refers to the local interface.

port

the port libtorrent ended up listening on.

socket_type

the type of listen socket this alert refers to.

portmap_error_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a NAT router was successfully found but some part of the port mapping request failed. It contains a text message that may help the user figure out what is wrong. This alert is not generated in case it appears the client is not running on a NAT:ed network or if it appears there is no NAT router that can be remote controlled to add port mappings.

struct portmap_error_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::port_mapping
   | alert_category::error;
   port_mapping_t const mapping;
   portmap_transport map_transport;
   aux::noexcept_movable<address> local_address;
   error_code const error;
};

mapping

refers to the mapping index of the port map that failed, i.e. the index returned from add_mapping().

map_transport

UPnP or NAT-PMP

local_address

the local network the port mapper is running on

error

tells you what failed.

portmap_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a NAT router was successfully found and a port was successfully mapped on it. On a NAT:ed network with a NAT-PMP capable router, this is typically generated once when mapping the TCP port and, if DHT is enabled, when the UDP port is mapped.

struct portmap_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::port_mapping;
   port_mapping_t const mapping;
   int const external_port;
   portmap_protocol const map_protocol;
   portmap_transport const map_transport;
   aux::noexcept_movable<address> local_address;
};

mapping

refers to the mapping index of the port map that failed, i.e. the index returned from add_mapping().

external_port

the external port allocated for the mapping.

local_address

the local network the port mapper is running on

portmap_log_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated to log informational events related to either UPnP or NAT-PMP. They contain a log line and the type (0 = NAT-PMP and 1 = UPnP). Displaying these messages to an end user is only useful for debugging the UPnP or NAT-PMP implementation. This alert is only posted if the alert_category::port_mapping_log flag is enabled in the alert mask.

struct portmap_log_alert final : alert
{
   std::string message () const override;
   char const* log_message () const;

   static constexpr alert_category_t static_category  = alert_category::port_mapping_log;
   portmap_transport const map_transport;
   aux::noexcept_movable<address> local_address;
};

char const* log_message () const;

fastresume_rejected_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a fast resume file has been passed to add_torrent() but the files on disk did not match the fast resume file. The error_code explains the reason why the resume file was rejected.

struct fastresume_rejected_alert final : torrent_alert
{
   std::string message () const override;
   char const* file_path () const;

   static constexpr alert_category_t static_category  = alert_category::status
   | alert_category::error;
   error_code error;
   operation_t op;
};

char const* file_path () const;

peer_blocked_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when an incoming peer connection, or a peer that's about to be added to our peer list, is blocked for some reason. This could be any of:

• the IP filter
• i2p mixed mode restrictions (a normal peer is not allowed on an i2p swarm)
• the port filter
• the peer has a low port and no_connect_privileged_ports is enabled
• the protocol of the peer is blocked (uTP/TCP blocking)

struct peer_blocked_alert final : peer_alert
{
   std::string message () const override;

   enum reason_t
   {
      ip_filter,
      port_filter,
      i2p_mixed,
      privileged_ports,
      utp_disabled,
      tcp_disabled,
      invalid_local_interface,
      ssrf_mitigation,
   };

   static constexpr alert_category_t static_category  = alert_category::ip_block;
   int const reason;
};

dht_announce_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a DHT node announces to an info-hash on our DHT node. It belongs to the alert_category::dht category.

struct dht_announce_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
   aux::noexcept_movable<address> ip;
   int port;
   sha1_hash info_hash;
};

dht_get_peers_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when a DHT node sends a get_peers message to our DHT node. It belongs to the alert_category::dht category.

struct dht_get_peers_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
   sha1_hash info_hash;
};

cache_flushed_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when the disk cache has been flushed for a specific torrent as a result of a call to torrent_handle::flush_cache(). This alert belongs to the alert_category::storage category, which must be enabled to let this alert through. The alert is also posted when removing a torrent from the session, once the outstanding cache flush is complete and the torrent does no longer have any files open.

struct cache_flushed_alert final : torrent_alert
{
   static constexpr alert_category_t static_category  = alert_category::storage;
};

lsd_peer_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when we receive a local service discovery message from a peer for a torrent we're currently participating in.

struct lsd_peer_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
};

trackerid_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted whenever a tracker responds with a trackerid. The tracker ID is like a cookie. libtorrent will store the tracker ID for this tracker and repeat it in subsequent announces.

struct trackerid_alert final : tracker_alert
{
   std::string message () const override;
   char const* tracker_id () const;

   static constexpr alert_category_t static_category  = alert_category::status;
};

char const* tracker_id () const;

dht_bootstrap_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when the initial DHT bootstrap is done.

struct dht_bootstrap_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
};

torrent_error_alert

Declared in "libtorrent/alert_types.hpp"

This is posted whenever a torrent is transitioned into the error state. If the error code is duplicate_torrent (error_code_enum) error, it suggests two magnet links ended up resolving to the same hybrid torrent. For more details, see BitTorrent v2 torrents.

struct torrent_error_alert final : torrent_alert
{
   std::string message () const override;
   char const* filename () const;

   static constexpr alert_category_t static_category  = alert_category::error | alert_category::status;
   error_code const error;
};

char const* filename () const;

torrent_need_cert_alert

Declared in "libtorrent/alert_types.hpp"

This is always posted for SSL torrents. This is a reminder to the client that the torrent won't work unless torrent_handle::set_ssl_certificate() is called with a valid certificate. Valid certificates MUST be signed by the SSL certificate in the .torrent file.

struct torrent_need_cert_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
};

incoming_connection_alert

Declared in "libtorrent/alert_types.hpp"

The incoming connection alert is posted every time we successfully accept an incoming connection, through any mean. The most straight-forward ways of accepting incoming connections are through the TCP listen socket and the UDP listen socket for uTP sockets. However, connections may also be accepted through a Socks5 or i2p listen socket, or via an SSL listen socket.

struct incoming_connection_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::peer;
   socket_type_t socket_type;
   aux::noexcept_movable<tcp::endpoint> endpoint;
};

socket_type

tells you what kind of socket the connection was accepted

endpoint

is the IP address and port the connection came from.

add_torrent_alert

Declared in "libtorrent/alert_types.hpp"

This alert is always posted when a torrent was attempted to be added and contains the return status of the add operation. The torrent handle of the new torrent can be found as the handle member in the base class. If adding the torrent failed, error contains the error code.

struct add_torrent_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   add_torrent_params params;
   error_code error;
};

params

This contains copies of the most important fields from the original add_torrent_params object, passed to add_torrent() or async_add_torrent(). Specifically, these fields are copied:

• version
• ti
• name
• save_path
• userdata
• tracker_id
• flags
• info_hash

the info_hash field will be updated with the info-hash of the torrent specified by ti.

error

set to the error, if one occurred while adding the torrent.

state_update_alert

Declared in "libtorrent/alert_types.hpp"

This alert is only posted when requested by the user, by calling session::post_torrent_updates() on the session. It contains the torrent status of all torrents that changed since last time this message was posted. Its category is alert_category::status, but it's not subject to filtering, since it's only manually posted anyway.

struct state_update_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   std::vector<torrent_status> status;
};

status

contains the torrent status of all torrents that changed since last time this message was posted. Note that you can map a torrent status to a specific torrent via its handle member. The receiving end is suggested to have all torrents sorted by the torrent_handle or hashed by it, for efficient updates.

session_stats_alert

Declared in "libtorrent/alert_types.hpp"

The session_stats_alert is posted when the user requests session statistics by calling post_session_stats() on the session object. This alert does not have a category, since it's only posted in response to an API call. It is not subject to the alert_mask filter.

the message() member function returns a string representation of the values that properly match the line returned in session_stats_header_alert::message().

this specific output is parsed by tools/parse_session_stats.py if this is changed, that parser should also be changed

struct session_stats_alert final : alert
{
   std::string message () const override;
   span<std::int64_t const> counters () const;

   static constexpr alert_category_t static_category  = {};
};

span<std::int64_t const> counters () const;

dht_error_alert

Declared in "libtorrent/alert_types.hpp"

posted when something fails in the DHT. This is not necessarily a fatal error, but it could prevent proper operation

struct dht_error_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error | alert_category::dht;
   error_code error;
   operation_t op;
};

error

the error code

op

the operation that failed

dht_immutable_item_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted as a response to a call to session::get_item(), specifically the overload for looking up immutable items in the DHT.

struct dht_immutable_item_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
   sha1_hash target;
   entry item;
};

target

the target hash of the immutable item. This must match the SHA-1 hash of the bencoded form of item.

item

the data for this item

dht_mutable_item_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted as a response to a call to session::get_item(), specifically the overload for looking up mutable items in the DHT.

struct dht_mutable_item_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
   std::array<char, 32> key;
   std::array<char, 64> signature;
   std::int64_t seq;
   std::string salt;
   entry item;
   bool authoritative;
};

key

the public key that was looked up

signature

the signature of the data. This is not the signature of the plain encoded form of the item, but it includes the sequence number and possibly the hash as well. See the dht_store document for more information. This is primarily useful for echoing back in a store request.

seq

the sequence number of this item

salt

the salt, if any, used to lookup and store this item. If no salt was used, this is an empty string

item

the data for this item

authoritative

the last response for mutable data is authoritative.

dht_put_alert

Declared in "libtorrent/alert_types.hpp"

this is posted when a DHT put operation completes. This is useful if the client is waiting for a put to complete before shutting down for instance.

struct dht_put_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
   sha1_hash target;
   std::array<char, 32> public_key;
   std::array<char, 64> signature;
   std::string salt;
   std::int64_t seq;
   int num_success;
};

target

the target hash the item was stored under if this was an immutable item.

public_key signature salt seq

if a mutable item was stored, these are the public key, signature, salt and sequence number the item was stored under.

num_success

DHT put operation usually writes item to k nodes, maybe the node is stale so no response, or the node doesn't support 'put', or the token for write is out of date, etc. num_success is the number of successful responses we got from the puts.

i2p_alert

Declared in "libtorrent/alert_types.hpp"

this alert is used to report errors in the i2p SAM connection

struct i2p_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   error_code error;
};

error

the error that occurred in the i2p SAM connection

dht_outgoing_get_peers_alert

Declared in "libtorrent/alert_types.hpp"

This alert is generated when we send a get_peers request It belongs to the alert_category::dht category.

struct dht_outgoing_get_peers_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::dht;
   sha1_hash info_hash;
   sha1_hash obfuscated_info_hash;
   aux::noexcept_movable<udp::endpoint> endpoint;
};

info_hash

the info_hash of the torrent we're looking for peers for.

obfuscated_info_hash

if this was an obfuscated lookup, this is the info-hash target actually sent to the node.

endpoint

the endpoint we're sending this query to

log_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted by some session wide event. Its main purpose is trouble shooting and debugging. It's not enabled by the default alert mask and is enabled by the alert_category::session_log bit. Furthermore, it's by default disabled as a build configuration.

struct log_alert final : alert
{
   std::string message () const override;
   char const* log_message () const;

   static constexpr alert_category_t static_category  = alert_category::session_log;
};

char const* log_message () const;

torrent_log_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted by torrent wide events. It's meant to be used for trouble shooting and debugging. It's not enabled by the default alert mask and is enabled by the alert_category::torrent_log bit. By default it is disabled as a build configuration.

struct torrent_log_alert final : torrent_alert
{
   std::string message () const override;
   char const* log_message () const;

   static constexpr alert_category_t static_category  = alert_category::torrent_log;
};

char const* log_message () const;

peer_log_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted by events specific to a peer. It's meant to be used for trouble shooting and debugging. It's not enabled by the default alert mask and is enabled by the alert_category::peer_log bit. By default it is disabled as a build configuration.

struct peer_log_alert final : peer_alert
{
   std::string message () const override;
   char const* log_message () const;

   enum direction_t
   {
      incoming_message,
      outgoing_message,
      incoming,
      outgoing,
      info,
   };

   static constexpr alert_category_t static_category  = alert_category::peer_log;
   char const* event_type;
   direction_t direction;
};

char const* log_message () const;

lsd_error_alert

Declared in "libtorrent/alert_types.hpp"

posted if the local service discovery socket fails to start properly. it's categorized as alert_category::error.

struct lsd_error_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   aux::noexcept_movable<address> local_address;
   error_code error;
};

local_address

the local network the corresponding local service discovery is running on

error

The error code

dht_lookup

Declared in "libtorrent/alert_types.hpp"

holds statistics about a current dht_lookup operation. a DHT lookup is the traversal of nodes, looking up a set of target nodes in the DHT for retrieving and possibly storing information in the DHT

struct dht_lookup
{
   char const* type;
   int outstanding_requests;
   int timeouts;
   int responses;
   int branch_factor;
   int nodes_left;
   int last_sent;
   int first_timeout;
   sha1_hash target;
};

type

string literal indicating which kind of lookup this is

outstanding_requests

the number of outstanding request to individual nodes this lookup has right now

timeouts

the total number of requests that have timed out so far for this lookup

responses

the total number of responses we have received for this lookup so far for this lookup

branch_factor

the branch factor for this lookup. This is the number of nodes we keep outstanding requests to in parallel by default. when nodes time out we may increase this.

nodes_left

the number of nodes left that could be queries for this lookup. Many of these are likely to be part of the trail while performing the lookup and would never end up actually being queried.

last_sent

the number of seconds ago the last message was sent that's still outstanding

first_timeout

the number of outstanding requests that have exceeded the short timeout and are considered timed out in the sense that they increased the branch factor

target

the node-id or info-hash target for this lookup

dht_stats_alert

Declared in "libtorrent/alert_types.hpp"

contains current DHT state. Posted in response to session::post_dht_stats().

struct dht_stats_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = {};
   std::vector<dht_lookup> active_requests;
   std::vector<dht_routing_bucket> routing_table;
   sha1_hash nid;
   aux::noexcept_movable<udp::endpoint> local_endpoint;
};

active_requests

a vector of the currently running DHT lookups.

routing_table

contains information about every bucket in the DHT routing table.

nid

the node ID of the DHT node instance

local_endpoint

the local socket this DHT node is running on

incoming_request_alert

Declared in "libtorrent/alert_types.hpp"

posted every time an incoming request from a peer is accepted and queued up for being serviced. This alert is only posted if the alert_category::incoming_request flag is enabled in the alert mask.

struct incoming_request_alert final : peer_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::incoming_request;
   peer_request req;
};

req

the request this peer sent to us

dht_log_alert

Declared in "libtorrent/alert_types.hpp"

debug logging of the DHT when alert_category::dht_log is set in the alert mask.

struct dht_log_alert final : alert
{
   std::string message () const override;
   char const* log_message () const;

   enum dht_module_t
   {
      tracker,
      node,
      routing_table,
      rpc_manager,
      traversal,
   };

   static constexpr alert_category_t static_category  = alert_category::dht_log;
   dht_module_t module;
};

char const* log_message () const;

dht_pkt_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted every time a DHT message is sent or received. It is only posted if the alert_category::dht_log alert category is enabled. It contains a verbatim copy of the message.

struct dht_pkt_alert final : alert
{
   std::string message () const override;
   span<char const> pkt_buf () const;

   enum direction_t
   {
      incoming,
      outgoing,
   };

   static constexpr alert_category_t static_category  = alert_category::dht_log;
   direction_t direction;
   aux::noexcept_movable<udp::endpoint> node;
};

span<char const> pkt_buf () const;

dht_get_peers_reply_alert

Declared in "libtorrent/alert_types.hpp"

Posted when we receive a response to a DHT get_peers request.

struct dht_get_peers_reply_alert final : alert
{
   std::string message () const override;
   int num_peers () const;
   std::vector<tcp::endpoint> peers () const;

   static constexpr alert_category_t static_category  = alert_category::dht_operation;
   sha1_hash info_hash;
};

dht_direct_response_alert

Declared in "libtorrent/alert_types.hpp"

This is posted exactly once for every call to session_handle::dht_direct_request. If the request failed, response() will return a default constructed bdecode_node.

struct dht_direct_response_alert final : alert
{
   std::string message () const override;
   bdecode_node response () const;

   static constexpr alert_category_t static_category  = alert_category::dht;
   client_data_t userdata;
   aux::noexcept_movable<udp::endpoint> endpoint;
};

picker_log_alert

Declared in "libtorrent/alert_types.hpp"

this is posted when one or more blocks are picked by the piece picker, assuming the verbose piece picker logging is enabled (see alert_category::picker_log).

struct picker_log_alert final : peer_alert
{
   std::string message () const override;
   std::vector<piece_block> blocks () const;

   static constexpr alert_category_t static_category  = alert_category::picker_log;
   static constexpr picker_flags_t partial_ratio  = 0_bit;
   static constexpr picker_flags_t prioritize_partials  = 1_bit;
   static constexpr picker_flags_t rarest_first_partials  = 2_bit;
   static constexpr picker_flags_t rarest_first  = 3_bit;
   static constexpr picker_flags_t reverse_rarest_first  = 4_bit;
   static constexpr picker_flags_t suggested_pieces  = 5_bit;
   static constexpr picker_flags_t prio_sequential_pieces  = 6_bit;
   static constexpr picker_flags_t sequential_pieces  = 7_bit;
   static constexpr picker_flags_t reverse_pieces  = 8_bit;
   static constexpr picker_flags_t time_critical  = 9_bit;
   static constexpr picker_flags_t random_pieces  = 10_bit;
   static constexpr picker_flags_t prefer_contiguous  = 11_bit;
   static constexpr picker_flags_t reverse_sequential  = 12_bit;
   static constexpr picker_flags_t backup1  = 13_bit;
   static constexpr picker_flags_t backup2  = 14_bit;
   static constexpr picker_flags_t end_game  = 15_bit;
   static constexpr picker_flags_t extent_affinity  = 16_bit;
   picker_flags_t const picker_flags;
};

picker_flags

this is a bitmask of which features were enabled for this particular pick. The bits are defined in the picker_flags_t enum.

session_error_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted when the session encounters a serious error, potentially fatal

struct session_error_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   error_code const error;
};

error

The error code, if one is associated with this error

dht_live_nodes_alert

Declared in "libtorrent/alert_types.hpp"

posted in response to a call to session::dht_live_nodes(). It contains the live nodes from the DHT routing table of one of the DHT nodes running locally.

struct dht_live_nodes_alert final : alert
{
   std::string message () const override;
   int num_nodes () const;
   std::vector<std::pair<sha1_hash, udp::endpoint>> nodes () const;

   static constexpr alert_category_t static_category  = alert_category::dht;
   sha1_hash node_id;
};

int num_nodes () const;
std::vector<std::pair<sha1_hash, udp::endpoint>> nodes () const;

session_stats_header_alert

Declared in "libtorrent/alert_types.hpp"

The session_stats_header alert is posted the first time post_session_stats() is called

the message() member function returns a string representation of the header that properly match the stats values string returned in session_stats_alert::message().

this specific output is parsed by tools/parse_session_stats.py if this is changed, that parser should also be changed

struct session_stats_header_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = {};
};

dht_sample_infohashes_alert

Declared in "libtorrent/alert_types.hpp"

posted as a response to a call to session::dht_sample_infohashes() with the information from the DHT response message.

struct dht_sample_infohashes_alert final : alert
{
   std::string message () const override;
   std::vector<sha1_hash> samples () const;
   int num_samples () const;
   int num_nodes () const;
   std::vector<std::pair<sha1_hash, udp::endpoint>> nodes () const;

   static constexpr alert_category_t static_category  = alert_category::dht_operation;
   sha1_hash node_id;
   aux::noexcept_movable<udp::endpoint> endpoint;
   time_duration const interval;
   int const num_infohashes;
};

std::vector<sha1_hash> samples () const;
int num_samples () const;

int num_nodes () const;

std::vector<std::pair<sha1_hash, udp::endpoint>> nodes () const;

block_uploaded_alert

Declared in "libtorrent/alert_types.hpp"

This alert is posted when a block intended to be sent to a peer is placed in the send buffer. Note that if the connection is closed before the send buffer is sent, the alert may be posted without the bytes having been sent to the peer. It belongs to the alert_category::upload category.

struct block_uploaded_alert final : peer_alert
{
   std::string message () const override;

   int const block_index;
   piece_index_t const piece_index;
};

alerts_dropped_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted to indicate to the client that some alerts were dropped. Dropped meaning that the alert failed to be delivered to the client. The most common cause of such failure is that the internal alert queue grew too big (controlled by alert_queue_size).

struct alerts_dropped_alert final : alert
{
   static_assert (num_alert_types <= abi_alert_count, "need to increase bitset. This is an ABI break");
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   std::bitset<abi_alert_count> dropped_alerts;
};

dropped_alerts

a bitmask indicating which alerts were dropped. Each bit represents the alert type ID, where bit 0 represents whether any alert of type 0 has been dropped, and so on.

socks5_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted with SOCKS5 related errors, when a SOCKS5 proxy is configured. It's enabled with the alert_category::error alert category.

struct socks5_alert final : alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   error_code error;
   operation_t op;
   aux::noexcept_movable<tcp::endpoint> ip;
};

error

the error

op

the operation that failed

ip

the endpoint configured as the proxy

file_prio_alert

Declared in "libtorrent/alert_types.hpp"

posted when a prioritize_files() or file_priority() update of the file priorities complete, which requires a round-trip to the disk thread.

If the disk operation fails this alert won't be posted, but a file_error_alert is posted instead, and the torrent is stopped.

struct file_prio_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage;
   error_code error;
   operation_t op;
};

error

the error

op

the operation that failed

oversized_file_alert

Declared in "libtorrent/alert_types.hpp"

this alert may be posted when the initial checking of resume data and files on disk (just existence, not piece hashes) completes. If a file belonging to the torrent is found on disk, but is larger than the file in the torrent, that's when this alert is posted. the client may want to call truncate_files() in that case, or perhaps interpret it as a sign that some other file is in the way, that shouldn't be overwritten.

struct oversized_file_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::storage;
};

torrent_conflict_alert

Declared in "libtorrent/alert_types.hpp"

this alert is posted when two separate torrents (magnet links) resolve to the same torrent, thus causing the same torrent being added twice. In that case, both torrents enter an error state with duplicate_torrent as the error code. This alert is posted containing the metadata. For more information, see BitTorrent v2 torrents. The torrent this alert originated from was the one that downloaded the

metadata (i.e. the handle member from the torrent_alert base class).

struct torrent_conflict_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::error;
   torrent_handle conflicting_torrent;
   std::shared_ptr<torrent_info> metadata;
};

conflicting_torrent

the handle to the torrent in conflict. The swarm associated with this torrent handle did not download the metadata, but the downloaded metadata collided with this swarm's info-hash.

metadata

the metadata that was received by one of the torrents in conflict. One way to resolve the conflict is to remove both failing torrents and re-add it using this metadata

peer_info_alert

Declared in "libtorrent/alert_types.hpp"

posted when torrent_handle::post_peer_info() is called

struct peer_info_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   std::vector<lt::peer_info> peer_info;
};

peer_info

the list of the currently connected peers

file_progress_alert

Declared in "libtorrent/alert_types.hpp"

posted when torrent_handle::post_file_progress() is called

struct file_progress_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::file_progress;
   aux::vector<std::int64_t, file_index_t> files;
};

files

the list of the files in the torrent

piece_info_alert

Declared in "libtorrent/alert_types.hpp"

posted when torrent_handle::post_download_queue() is called

struct piece_info_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::piece_progress;
   std::vector<partial_piece_info> piece_info;
   std::vector<block_info> block_data;
};

piece_info

info about pieces being downloaded for the torrent

block_data

storage for block_info pointers in partial_piece_info objects

piece_availability_alert

Declared in "libtorrent/alert_types.hpp"

posted when torrent_handle::post_piece_availability() is called

struct piece_availability_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   std::vector<int> piece_availability;
};

piece_availability

info about pieces being downloaded for the torrent

tracker_list_alert

Declared in "libtorrent/alert_types.hpp"

posted when torrent_handle::post_trackers() is called

struct tracker_list_alert final : torrent_alert
{
   std::string message () const override;

   static constexpr alert_category_t static_category  = alert_category::status;
   std::vector<announce_entry> trackers;
};

trackers

list of trackers and their status for the torrent

alert

Declared in "libtorrent/alert.hpp"

The alert class is the base class that specific messages are derived from. alert types are not copyable, and cannot be constructed by the client. The pointers returned by libtorrent are short lived (the details are described under session_handle::pop_alerts())

struct alert
{
   time_point timestamp () const;
   virtual int type () const noexcept = 0;
   virtual char const* what () const noexcept = 0;
   virtual std::string message () const = 0;
   virtual alert_category_t category () const noexcept = 0;

   static constexpr alert_category_t error_notification  = 0_bit;
   static constexpr alert_category_t peer_notification  = 1_bit;
   static constexpr alert_category_t port_mapping_notification  = 2_bit;
   static constexpr alert_category_t storage_notification  = 3_bit;
   static constexpr alert_category_t tracker_notification  = 4_bit;
   static constexpr alert_category_t connect_notification  = 5_bit;
   static constexpr alert_category_t status_notification  = 6_bit;
   static constexpr alert_category_t ip_block_notification  = 8_bit;
   static constexpr alert_category_t performance_warning  = 9_bit;
   static constexpr alert_category_t dht_notification  = 10_bit;
   static constexpr alert_category_t session_log_notification  = 13_bit;
   static constexpr alert_category_t torrent_log_notification  = 14_bit;
   static constexpr alert_category_t peer_log_notification  = 15_bit;
   static constexpr alert_category_t incoming_request_notification  = 16_bit;
   static constexpr alert_category_t dht_log_notification  = 17_bit;
   static constexpr alert_category_t dht_operation_notification  = 18_bit;
   static constexpr alert_category_t port_mapping_log_notification  = 19_bit;
   static constexpr alert_category_t picker_log_notification  = 20_bit;
   static constexpr alert_category_t file_progress_notification  = 21_bit;
   static constexpr alert_category_t piece_progress_notification  = 22_bit;
   static constexpr alert_category_t upload_notification  = 23_bit;
   static constexpr alert_category_t block_progress_notification  = 24_bit;
   static constexpr alert_category_t all_categories  = alert_category_t::all();
};

time_point timestamp () const;

virtual int type () const noexcept = 0;

std::vector<alert*> alerts;
ses.pop_alerts(&alerts);
for (alert* a : alerts) {
        switch (a->type()) {

                case read_piece_alert::alert_type:
                {
                        auto* p = static_cast<read_piece_alert*>(a);
                        if (p->ec) {
                                // read_piece failed
                                break;
                        }
                        // use p
                        break;
                }
                case file_renamed_alert::alert_type:
                {
                        // etc...
                }
        }
}

virtual char const* what () const noexcept = 0;

virtual std::string message () const = 0;

virtual alert_category_t category () const noexcept = 0;

alert_cast()

Declared in "libtorrent/alert.hpp"

template <typename T> T const* alert_cast (alert const* a);
template <typename T> T* alert_cast (alert* a);

When you get an alert, you can use alert_cast<> to attempt to cast the pointer to a specific alert type, in order to query it for more information.

operation_name()

Declared in "libtorrent/operations.hpp"

char const* operation_name (operation_t op);

maps an operation id (from peer_error_alert and peer_disconnected_alert) to its name. See operation_t for the constants

enum operation_t

Declared in "libtorrent/operations.hpp"

int

Declared in "libtorrent/alert_types.hpp"

user_alert_id

user defined alerts should use IDs greater than this

num_alert_types

this constant represents "max_alert_index" + 1

alert_category_t

Declared in "libtorrent/alert.hpp"

error

Enables alerts that report an error. This includes:

• tracker errors
• tracker warnings
• file errors
• resume data failures
• web seed errors
• .torrent files errors
• listen socket errors
• port mapping errors

peer

Enables alerts when peers send invalid requests, get banned or snubbed.

port_mapping

Enables alerts for port mapping events. For NAT-PMP and UPnP.

storage

Enables alerts for events related to the storage. File errors and synchronization events for moving the storage, renaming files etc.

tracker

Enables all tracker events. Includes announcing to trackers, receiving responses, warnings and errors.

connect

Low level alerts for when peers are connected and disconnected.

status

Enables alerts for when a torrent or the session changes state.

ip_block

Alerts when a peer is blocked by the ip blocker or port blocker.

performance_warning

Alerts when some limit is reached that might limit the download or upload rate.

dht

Alerts on events in the DHT node. For incoming searches or bootstrapping being done etc.

stats

If you enable these alerts, you will receive a stats_alert approximately once every second, for every active torrent. These alerts contain all statistics counters for the interval since the lasts stats alert.

session_log

Enables debug logging alerts. These are available unless libtorrent was built with logging disabled (TORRENT_DISABLE_LOGGING). The alerts being posted are log_alert and are session wide.

torrent_log

Enables debug logging alerts for torrents. These are available unless libtorrent was built with logging disabled (TORRENT_DISABLE_LOGGING). The alerts being posted are torrent_log_alert and are torrent wide debug events.

peer_log

Enables debug logging alerts for peers. These are available unless libtorrent was built with logging disabled (TORRENT_DISABLE_LOGGING). The alerts being posted are peer_log_alert and low-level peer events and messages.

incoming_request

enables the incoming_request_alert.

dht_log

enables dht_log_alert, debug logging for the DHT

dht_operation

enable events from pure dht operations not related to torrents

port_mapping_log

enables port mapping log events. This log is useful for debugging the UPnP or NAT-PMP implementation

picker_log

enables verbose logging from the piece picker.

file_progress

alerts when files complete downloading

piece_progress

alerts when pieces complete downloading or fail hash check

upload

alerts when we upload blocks to other peers

block_progress

alerts on individual blocks being requested, downloading, finished, rejected, time-out and cancelled. This is likely to post alerts at a high rate.

all

The full bitmask, representing all available categories.

since the enum is signed, make sure this isn't interpreted as -1. For instance, boost.python does that and fails when assigning it to an unsigned parameter.

hasher

Declared in "libtorrent/hasher.hpp"

this is a SHA-1 hash class.

You use it by first instantiating it, then call update() to feed it with data. i.e. you don't have to keep the entire buffer of which you want to create the hash in memory. You can feed the hasher parts of it at a time. When You have fed the hasher with all the data, you call final() and it will return the sha1-hash of the data.

The constructor that takes a char const* and an integer will construct the sha1 context and feed it the data passed in.

If you want to reuse the hasher object once you have created a hash, you have to call reset() to reinitialize it.

The built-in software version of sha1-algorithm was implemented by Steve Reid and released as public domain. For more info, see src/sha1.cpp.

class hasher
{
   hasher ();
   hasher& operator= (hasher const&) &;
   hasher (hasher const&);
   explicit hasher (span<char const> data);
   hasher (char const* data, int len);
   hasher& update (span<char const> data);
   hasher& update (char const* data, int len);
   sha1_hash final ();
   void reset ();
};

hasher& operator= (hasher const&) &;
hasher (hasher const&);
explicit hasher (span<char const> data);
hasher (char const* data, int len);

hasher& update (span<char const> data);
hasher& update (char const* data, int len);

sha1_hash final ();

void reset ();

hasher256

Declared in "libtorrent/hasher.hpp"

class hasher256
{
   hasher256 ();
   hasher256& operator= (hasher256 const&) &;
   explicit hasher256 (span<char const> data);
   hasher256 (hasher256 const&);
   hasher256 (char const* data, int len);
   hasher256& update (char const* data, int len);
   hasher256& update (span<char const> data);
   sha256_hash final ();
   void reset ();
   ~hasher256 ();
};

hasher256& operator= (hasher256 const&) &;
explicit hasher256 (span<char const> data);
hasher256 (hasher256 const&);
hasher256 (char const* data, int len);