Socket
A GSocket is a low-level networking primitive. It is a more or less direct mapping of the BSD socket API in a portable GObject based API. It supports both the UNIX socket implementations and winsock2 on Windows.
GSocket is the platform independent base upon which the higher level network primitives are based. Applications are not typically meant to use it directly, but rather through classes like class@Gio.SocketClient, class@Gio.SocketService and class@Gio.SocketConnection. However there may be cases where direct use of GSocket is useful.
GSocket implements the iface@Gio.Initable interface, so if it is manually constructed by e.g. ctor@GObject.Object.new you must call method@Gio.Initable.init and check the results before using the object. This is done automatically in ctor@Gio.Socket.new and ctor@Gio.Socket.new_from_fd, so these functions can return NULL.
Sockets operate in two general modes, blocking or non-blocking. When in blocking mode all operations (which don’t take an explicit blocking parameter) block until the requested operation is finished or there is an error. In non-blocking mode all calls that would block return immediately with a G_IO_ERROR_WOULD_BLOCK error. To know when a call would successfully run you can call method@Gio.Socket.condition_check, or method@Gio.Socket.condition_wait. You can also use method@Gio.Socket.create_source and attach it to a type@GLib.MainContext to get callbacks when I/O is possible. Note that all sockets are always set to non blocking mode in the system, and blocking mode is emulated in GSocket.
When working in non-blocking mode applications should always be able to handle getting a G_IO_ERROR_WOULD_BLOCK error even when some other function said that I/O was possible. This can easily happen in case of a race condition in the application, but it can also happen for other reasons. For instance, on Windows a socket is always seen as writable until a write returns G_IO_ERROR_WOULD_BLOCK.
GSockets can be either connection oriented or datagram based. For connection oriented types you must first establish a connection by either connecting to an address or accepting a connection from another address. For connectionless socket types the target/source address is specified or received in each I/O operation.
All socket file descriptors are set to be close-on-exec.
Note that creating a GSocket causes the signal SIGPIPE to be ignored for the remainder of the program. If you are writing a command-line utility that uses GSocket, you may need to take into account the fact that your program will not automatically be killed if it tries to write to stdout after it has been closed.
Like most other APIs in GLib, GSocket is not inherently thread safe. To use a GSocket concurrently from multiple threads, you must implement your own locking.
Nagle’s algorithm
Since GLib 2.80, GSocket will automatically set the TCP_NODELAY option on all G_SOCKET_TYPE_STREAM sockets. This disables Nagle’s algorithm as it typically does more harm than good on modern networks.
If your application needs Nagle’s algorithm enabled, call method@Gio.Socket.set_option after constructing a GSocket to enable it:
socket = g_socket_new (…, G_SOCKET_TYPE_STREAM, …);
if (socket != NULL)
{
g_socket_set_option (socket, IPPROTO_TCP, TCP_NODELAY, FALSE, &local_error);
// handle error if needed
}Skipped during bindings generation
parameter
condition: C Type GIOCondition is ignoredparameter
condition: C Type GIOCondition is ignoredparameter
condition: C Type GIOCondition is ignoredparameter
value: value: Out parameter is not supportedparameter
buffer: buffer: Out parameter is not supportedparameter
address: address: Out parameter is not supportedparameter
address: address: Out parameter is not supportedmethod
receive_message: In/Out parameter is not supportedparameter
messages: InputMessageparameter
buffer: buffer: Out parameter is not supportedparameter
buffer: Array parameter of type guint8 is not supportedparameter
vectors: OutputVectorparameter
vectors: OutputVectorparameter
messages: OutputMessageparameter
buffer: Array parameter of type guint8 is not supportedparameter
buffer: Array parameter of type guint8 is not supportedmethod
local-address: Property getter throwsmethod
remote-address: Property getter throwsmethod
type: Property has no getter nor setter
Since
2.22
Constructors
Creates a new #GSocket with the defined family, type and protocol. If @protocol is 0 (%G_SOCKET_PROTOCOL_DEFAULT) the default protocol type for the family and type is used.
Creates a new #GSocket from a native file descriptor or winsock SOCKET handle.
Properties
The socket’s address family.
The number of outstanding connections in the listen queue.
Whether outgoing multicast packets loop back to the local host.
Time-to-live out outgoing multicast packets
The ID of the protocol to use, or -1 for unknown.
Functions
Accept incoming connections on a connection-based socket. This removes the first outstanding connection request from the listening socket and creates a #GSocket object for it.
When a socket is created it is attached to an address family, but it doesn't have an address in this family. g_socket_bind() assigns the address (sometimes called name) of the socket.
Checks and resets the pending connect error for the socket. This is used to check for errors when g_socket_connect() is used in non-blocking mode.
Connect the socket to the specified remote address.
Creates a #GSocketConnection subclass of the right type for
Get the amount of data pending in the OS input buffer, without blocking.
Gets the blocking mode of the socket. For details on blocking I/O, see g_socket_set_blocking().
Gets the broadcast setting on @socket; if true, it is possible to send packets to broadcast addresses.
Returns the credentials of the foreign process connected to this socket, if any (e.g. it is only supported for %G_SOCKET_FAMILY_UNIX sockets).
Gets the socket family of the socket.
Gets the keepalive mode of the socket. For details on this, see g_socket_set_keepalive().
Gets the listen backlog setting of the socket. For details on this, see g_socket_set_listen_backlog().
Try to get the local address of a bound socket. This is only useful if the socket has been bound to a local address, either explicitly or implicitly when connecting.
Gets the multicast loopback setting on @socket; if true (the default), outgoing multicast packets will be looped back to multicast listeners on the same host.
Gets the multicast time-to-live setting on @socket; see g_socket_set_multicast_ttl() for more details.
Gets the socket protocol id the socket was created with. In case the protocol is unknown, -1 is returned.
Try to get the remote address of a connected socket. This is only useful for connection oriented sockets that have been connected.
Gets the socket type of the socket.
Gets the timeout setting of the socket. For details on this, see g_socket_set_timeout().
Initializes the object implementing the interface.
Check whether the socket is connected. This is only useful for connection-oriented sockets.
Registers @socket to receive multicast messages sent to @group.
Registers @socket to receive multicast messages sent to @group.
Removes @socket from the multicast group defined by @group, @iface, and @source_specific (which must all have the same values they had when you joined the group).
Removes @socket from the multicast group defined by @group, @iface, and @source_specific (which must all have the same values they had when you joined the group).
Receives data (up to @size bytes) from a socket.
Sets the blocking mode of the socket. In blocking mode all operations (which don’t take an explicit blocking parameter) block until they succeed or there is an error. In non-blocking mode all functions return results immediately or with a %G_IO_ERROR_WOULD_BLOCK error.
Sets whether @socket should allow sending to broadcast addresses. This is false by default.
Sets or unsets the %SO_KEEPALIVE flag on the underlying socket. When this flag is set on a socket, the system will attempt to verify that the remote socket endpoint is still present if a sufficiently long period of time passes with no data being exchanged. If the system is unable to verify the presence of the remote endpoint, it will automatically close the connection.
Sets the maximum number of outstanding connections allowed when listening on this socket. If more clients than this are connecting to the socket and the application is not handling them on time then the new connections will be refused.
Sets whether outgoing multicast packets will be received by sockets listening on that multicast address on the same host. This is true by default.
Sets the time-to-live for outgoing multicast datagrams on @socket. By default, this is 1, meaning that multicast packets will not leave the local network.
Sets the time in seconds after which I/O operations on @socket will time out if they have not yet completed.
Checks if a socket is capable of speaking IPv4.