Listening port and connecting.

For multiplayer, I know that you can use the console node and use the command “travel mapname?listen” or “travel mapname?listen” to create a server. Then, the client can use “travel serverIP” or “open serverIP” to connect to the listening server.

But, I am not sure how to set the listening/connecting port. When I do something like “travel mapname?listen?port=4237” and then “travel”, it doesn’t work

Also, whats the difference between travel and open?