SDL Wiki
(This function is part of SDL_net, a separate library from SDL.)


Create and bind a new datagram socket.


SDLNet_DatagramSocket * SDLNet_CreateDatagramSocket(SDLNet_Address *addr, Uint16 port);

Function Parameters

address the local address to listen for connections on, or NULL.
the port on the local address to listen for connections on, or zero for the system to decide.

Return Value

Returns a new SDLNet_DatagramSocket, or NULL on error; call SDL_GetError() for details.


Datagram sockets follow different rules than stream sockets. They are not a reliable stream of bytes but rather packets, they are not limited to talking to a single other remote system, they do not maintain a single "connection" that can be dropped, and they more nimble about network failures at the expense of being more complex to use. What makes sense for your app depends entirely on what your app is trying to accomplish.

Generally the idea of a datagram socket is that you send data one chunk ("packet") at a time to any address you want, and it arrives whenever it gets there, even if later packets get there first, and maybe it doesn't get there at all, and you don't know when anything of this happens by default.

This function creates a new datagram socket.

This function does not block, and is not asynchronous, as the system can decide immediately if it can create a socket or not. If this returns success, you can immediately start talking to the network.

You can specify an address to listen for connections on; this address must be local to the system, and probably one returned by SDLNet_GetLocalAddresses(), but almost always you just want to specify NULL here, to listen on any address available to the app.

If you need to bind to a specific port (like a server), you should specify it in the port argument; datagram servers should do this, so they can be reached at a well-known port. If you only plan to initiate communications (like a client), you should specify 0 and let the system pick an unused port. Only one process can bind to a specific port at a time, so if you aren't acting as a server, you should choose 0. Datagram sockets can send individual packets to any port, so this just declares where data will arrive for your socket.

Datagram sockets don't employ any protocol (above the UDP level), so they can talk to apps that aren't using SDL_net, but if you want to speak any protocol beyond arbitrary packets of bytes, such as WebRTC, you'll have to implement that yourself on top of the stream socket.

Unlike BSD sockets or WinSock, you specify the port as a normal integer; you do not have to byteswap it into "network order," as the library will handle that for you.

Thread Safety

It is safe to call this function from any thread.


This function is available since SDL_Net 3.0.0.


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