tcpip() does the equivalent of bind() without SO_REUSEADDR https://stackoverflow.com/questions/14388706/socket-options-so-reuseaddr-and-so-reuseport-how-do-they-differ-do-they-mean-t
If you need multiple simultaneous connections, they will have to be on different ports.
One strategy in common use (by some of the key daemons, but not so much with user programs) is to publish a port for the client to make the connection to (e.g., the 30000), but instead of holding on to that port for the entire conversation, instead the server creates a new listener on another port, and responds to the client telling it what port the listener was created on, and then ends the connection. All of the clients need to talk to the same master port to get told what port the conversation will take place on, but those conversations are short and any refused connection can be retried a short time later to get the system a chance to finish the previous (short) conversation.
