[Boost-users] Bind to first available port

I know how to do this with Windows sockets, but how do I bind a UDP listen socket to the first available port? I want to send a packet from client to the server to subscribe to data and tell the server what port to send the subscribed data to. I don't care what port the client listens to. If I hard code it, I can only run a single client on a PC. I want to bind to the first available one so I can run as many clients on the same PC as I want.