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Connection Class

A Connection object represents a connection between a local Port object and a remote computer, specified by an IP address/port pair. The P2PTransport class manages a number of connections, one between each remote address and each local address, and chooses the best one for sending data. Connection objects are responsible for monitoring the health of their writability, and reporting this, as well as sending out pings to keep a connection open, if necessary, though these tasks are handled automatically. Connections send the Connection::SignalReadPacket signal when new data arrives over the network; P2PTransportChannel calls Send to send data out to the remote computer.

This is a pure virtual class. libjingle includes two subclasses of Connection: ProxyConnection, which defers most of the work to the Port object, and TCPConnection, which connects directly with the socket itself. This page describes both subclasses; TCPConnection differs only in the addition of a constructor, a destructor, and the Socket function. A TCPConnection object works with TCPPort. A ProxyConnection works with UDPPort , StunPort, and RelayPort.

Connection defines the following timeout values:

Const Name Description Value
CONNECTION_READ_TIMEOUT The length of time we wait before timing out readability on a connection. 30 seconds
CONNECTION_WRITE_TIMEOUT The length of time we wait before timing out writability on a connection. 15 seconds
CONNECTION_WRITE_CONNECT_TIMEOUT The length of time we wait before we become unwritable. 5 seconds
CONNECTION_WRITE_CONNECT_FAILURES The number of pings that must fail to respond before we become unwritable. 5 pings
CONNECTION_RESPONSE_TIMEOUT This is the length of time that we wait for a ping response to come back. 5 seconds.

Syntax

class Connection : public MessageHandler, 
                   public sigslot::has_slots<> 

The following table describes the protected and public methods of Connection and the inherited classes. The methods shown are not thread-safe, and can be called on any thread, but you should call them from the worker thread.

Methods

Connection defines the following public or protected members.

Name Description
void CheckTimeout() Checks whether this connection is unreadable/writable and should be destroyed. If so, it calls Destroy.
~Connection Destructor.
Connection(Port *port, size_t index, const Candidate &candidate) Constructor. Call it with the local Port object, the index of this connection in the caller's vector of connections, and the address of a remote candidate.
void Destroy() Causes this connection to be deleted.
virtual int GetError() = 0 Retrieves the error if Send returns a value less than zero.
uint32 last_ping_sent() Returns the time that the last ping was sent (absolute time value).
Candidate& local_candidate() Retrieves the local part of this connection. Contrast this with remote_candidate.
void OnConnectionRequestErrorResponse(StunMessage *response, uint32 rtt) Called when a connection request fails.
void OnConnectionRequestResponse(StunMessage *response, uint32 rtt) Called when a connection request succeeds.
void OnMessage(Message *pmsg) Messaging loop message receiver method.
void OnReadPacket(const char *data, size_t size) Called when the port reads a packet from the other computer.
void OnSendStunPacket(const void *data, size_t size) Called when a STUN packet is ready to send.
void Ping(uint32 now) Sends a ping across a connection. now should be the current time.
Port* port() Returns a pointer to the Port object associated with this connection.
const Port* port() const A const version of port.
void Prune() Clears pending messages in this connection. Called when a connection is determined no longer useful to this application. It is not destroyed in case the other side wants to use it, but we can safely stop pinging it, and we can allow it to time out if the other side stops using it as well.
bool pruned() Returns a boolean value indicating whether or not this connection has been pruned.
ReadState read_state() const Returns a ReadState enumerated value indicating the current read state. ReadState values are listed below. See also write_state.
void ReceivedPing() Called whenever a valid ping is received on this connection. This is public because the connection intercepts the first ping.
size_t recv_bytes_second() Read speed of this connection, in bytes per second.
size_t recv_total_bytes() Total number of bytes received over this connection.
const Candidate& remote_candidate() const The remote connection. Contrast this with local_candidate.
uint32 rtt() const Estimate of the round-trip time over this connection, in milliseconds.
virtual int Send(const void *data, size_t size)=0 Sends a packet of data asynchronously.
size_t sent_bytes_second() The write speed of this connection, in bytes per second.
size_t sent_total_bytes() Total number of bytes sent over this connection.
void set_connected(bool value) Sets a value indicating whether or not the connection is writable. If False and the read state is STATE_READ_TIMEOUT, the connection will destroy itself.
void set_read_state(ReadState value) Sets the read state of the connection. If the connection is both unwritable and unreadable, it will trigger the destruction of the connection.
set_write_state(WriteState value) Sets the write state of this connection. f False and the read state is STATE_READ_TIMEOUT, the connection will destroy itself.
void UpdateState(uint32 now) Checks the read and write states of this connection. If both are bad, it will trigger destruction of the connection. now is the current time, which is compared against various timeouts.
WriteState write_state() Returns the current write state. Possible values are listed below. See also read_state.
TCPConnection(TCPPort* port, const Candidate& candidate, AsyncTCPSocket* socket) Constructor for TCPConnection objects. This is called by TCPPort, which passes in itself, a remote candidate address, and a socket that handles the connection.
TCPPort* TCPPort() Returns the Port object for a TCPConnection.

Enumerations

Name Description
ReadState

Indicates the readability of this connection. The following values are defined:

  • STATE_READABLE   The application has received pings recently.
  • STATE_READ_TIMEOUT   The application hasn't received pings recently.
WriteState

Indicates the writeability of this connection. The following values are defined:

  • STATE_WRITABLE   The application has received ping responses recently.
  • STATE_WRITE_CONNECT   The application has had a few ping failures.
  • STATE_WRITE_TIMEOUT   The application has had many ping failures.

Signals

SignalStateChange<Connection *>
Sent when the state of the connection has changed.
SignalDestroyed<Connection *>
Sent when the connection has been destroyed.
SignalReadPacket<Connection *, const char *, size_t >
Sent when an incoming packet of data has been received from a Port object.

Attributes: public

Declaration file: talk/p2p/base/port.h

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