Receive a new packet that a remote system sent to a datagram socket.
int SDLNet_ReceiveDatagram(SDLNet_DatagramSocket *sock, SDLNet_Datagram **dgram);
|sock||the datagram socket to send data through|
|buf||a pointer to the data to send as a single packet.|
|buflen||the size of the data to send, in bytes.|
Returns 0 if data sent or queued for transmission, -1 on failure; call SDL_GetError() for details.
Datagram sockets send packets of data. They either arrive as complete packets or they don't arrive at all, so you'll never receive half a packet.
This call never blocks; if no new data isn't available at the time of the call, it returns 0 immediately. The caller can try again later.
On a successful call to this function, it returns zero, even if no new packets are available, so you should check for a successful return and a non-NULL value in
*dgram to decide if a new packet is available.
You must pass received packets to SDLNet_DestroyDatagram when you are done with them. If you want to save the sender's address past this time, it is safe to call SDLNet_RefAddress() on the address and hold onto the pointer, so long as you call SDLNet_UnrefAddress() on it when you are done with it.
Since datagrams can arrive from any address or port on the network without prior warning, this information is available in the SDLNet_Datagram object that is provided by this function, and this is the only way to know who to reply to. Even if you aren't acting as a "server," packets can still arrive at your socket if someone sends one.
If there's a fatal error, this function will return -1. Datagram sockets generally won't report failures, because there is no state like a "connection" to fail at this level, but may report failure for unrecoverable system-level conditions; once a datagram socket fails, you should assume it is no longer usable and should destroy it with SDL_DestroyDatagramSocket().
You should not operate on the same socket from multiple threads at the same time without supplying a serialization mechanism. However, different threads may access different sockets at the same time without problems.
This function is available since SDL_Net 3.0.0.