Try using a different port for both. If one is using port 6346, then make the other use a different port to connect thru. That may mean manual port forwarading for one of them. Try a port between (49152 - 65535) for example.

Unless you tell us the router/modem device brand & model number then I can't direct you to instructions for this if you're not sure (but that's if I can find such.)