This form appears when you press
CHANGE UDP port in the parent Reception
of Nmea 0183 Sentences form. You should enter the UDP port
number that the multiplexer uses.
UDP is a connection-less protocol. This means that the sender (the
multiplexer in this case) just sends the messages and does not
care if they are received or not. It suffices to specify the port
number to listen to and there is no need to specify an IP Address.
This is so because the multiplexer uses the IP Address
192.168.4.255 which means that all clients in the same sub net and
listening on the specified port number will receive the messages.