the buffer containing the data to send. [array length=size]
the number of bytes to send
whether to do blocking or non-blocking I/O
a GCancellable or NULL. [allow-none]
Number of bytes written (which may be less than size), or -1 on error
GException on failure.
This behaves exactly the same as g_socket_send(), except that the choice of blocking or non-blocking behavior is determined by the blocking argument rather than by socket's properties. Since 2.26