Get the amount of data pending in the OS input buffer, without blocking.
socket is a UDP or SCTP socket, this will return the size of
just the next packet, even if additional packets are buffered after
Note that on Windows, this function is rather inefficient in the
UDP case, and so if you know any plausible upper bound on the size
of the incoming packet, it is better to just do a
g_socket_receive() with a buffer of that size, rather than calling
g_socket_get_available_bytes() first and then doing a receive of
exactly the right size.
Available since: 2.32