How is default port determined if not given in config?

[Christoph Mayer]

If no port number is given, tcp and udp currently bind to 41402 (see AribaModule.cpp). If two nodes run locally both choose this port and the latter one will fail to bind. Actually each node could choose a random port (best > 1024) and see which one it can bind to.

Or should all nodes bind to a default if none is given in the config? This would of course not allow multiple nodes one one machine as they would try to bind on the same default port.