since: 2.22


g_socket_send_message (
  GSocket* socket,
  GSocketAddress* address,
  GOutputVector* vectors,
  gint num_vectors,
  GSocketControlMessage** messages,
  gint num_messages,
  gint flags,
  GCancellable* cancellable,
  GError** error


Send data to address on socket. For sending multiple messages see g_socket_send_messages(); for easier use, see g_socket_send() and g_socket_send_to().

If address is NULL then the message is sent to the default receiver (set by g_socket_connect()).

vectors must point to an array of GOutputVector structs and num_vectors must be the length of this array. (If num_vectors is -1, then vectors is assumed to be terminated by a GOutputVector with a NULL buffer pointer.) The GOutputVector structs describe the buffers that the sent data will be gathered from. Using multiple GOutputVectors is more memory-efficient than manually copying data from multiple sources into a single buffer, and more network-efficient than making multiple calls to g_socket_send().

messages, if non-NULL, is taken to point to an array of num_messages GSocketControlMessage instances. These correspond to the control messages to be sent on the socket. If num_messages is -1 then messages is treated as a NULL-terminated array.

flags modify how the message is sent. The commonly available arguments for this are available in the GSocketMsgFlags enum, but the values there are the same as the system values, and the flags are passed in as-is, so you can pass in system-specific flags too.

If the socket is in blocking mode the call will block until there is space for the data in the socket queue. If there is no space available and the socket is in non-blocking mode a G_IO_ERROR_WOULD_BLOCK error will be returned. To be notified when space is available, wait for the G_IO_OUT condition. Note though that you may still receive G_IO_ERROR_WOULD_BLOCK from g_socket_send() even if you were previously notified of a G_IO_OUT condition. (On Windows in particular, this is very common due to the way the underlying APIs work.)

The sum of the sizes of each GOutputVector in vectors must not be greater than G_MAXSSIZE. If the message can be larger than this, then it is mandatory to use the g_socket_send_message_with_timeout() function.

On error -1 is returned and error is set accordingly.

Available since: 2.22



Type: GSocketAddress

A GSocketAddress, or NULL.

The argument can be NULL.
The data is owned by the caller of the function.

Type: An array of GOutputVector

An array of GOutputVector structs.

The length of the array is specified in the num_vectors argument.
The data is owned by the caller of the function.

Type: gint

The number of elements in vectors, or -1


Type: An array of GSocketControlMessage*

A pointer to an array of GSocketControlMessages, or NULL.

The argument can be NULL.
The length of the array is specified in the num_messages argument.
The data is owned by the caller of the function.

Type: gint

Number of elements in messages, or -1.


Type: gint

An int containing GSocketMsgFlags flags, which may additionally contain other platform specific flags


Type: GCancellable

A %GCancellable or NULL.

The argument can be NULL.
The data is owned by the caller of the function.

Type: GError **

The return location for a recoverable error.

The argument can be NULL.
If the return location is not NULL, then you must initialize it to a NULL GError*.
The argument will left initialized to NULL by the method if there are no errors.
In case of error, the argument will be set to a newly allocated GError; the caller will take ownership of the data, and be responsible for freeing it.

Return value

Type: gssize

Number of bytes written (which may be less than size), or -1 on error.