Normally you establish one listening instance on a given port. You can, however, setup a "shared" listening port that will properly deliver data to devices based on their sending IP.
To do this you simply setup two devices, like normal, that both use the same UDP port but also add
receiveFrom to the connection string with the source IP of the device, e.g.:
localport=4712; transportProtocol=UDP; interface=0.0.0.0; receiveFrom=192.168.0.11
As long as there is a
receiveFrom IP defined in the connection string, the system will know to share an IP and properly pick up data for the device based on it's incoming IP address.
Hope that helps!