Ok great, thanks. Yah it seems the port number doesn't matter so long as it's not being used by a registered application currently running and ideally the port numbers should be 49152 or above. You can have ports from 1024 upwards also but these are registered with the port-management people so certain applications may conflict with you. I guess either way you have to keep searching for a port number until you find an open one, and it's not likely that they'll all (or even many) be used.
So long as the computer you are sending to is reading the port number that you are sending to, the message should get there (assuming it doesn't get lost), so the ports for the sender and receiver don't have to be the same. The send-to port has to be the same as the receive-from port for a given computer, but I guess you could also have dedicated send and receive ports or however you want to do it.
So long as the computer you are sending to is reading the port number that you are sending to, the message should get there (assuming it doesn't get lost), so the ports for the sender and receiver don't have to be the same. The send-to port has to be the same as the receive-from port for a given computer, but I guess you could also have dedicated send and receive ports or however you want to do it.