Search:

Can you write a small program that shows the error, execute the program and copy and paste the program and the full text of the error message here?

Use a ServerSocket to listen on at a port for future communications.

Use threads to allow sending on one socket while listening at another port.

I'm not sure what you are asking. The Socket constructor uses an IP address and port for the remote, server host.

How do you specify what port the client is to use?
You need to open a Socket...