Fix crash if a packet fails to reach the client

From the POSIX manpages: ENETUNREACH Network unreachable (POSIX.1-2001).

This is an error that, albeit quite rare, can occur if a packet fails to reach a client and bounces back to the server. This normally happens if an IP address gets invalidated while a packet to that address is in transit, as the PPP routing is then clearing out those addresses, making the packet unroutable. People with flaky internet connections are more likely to run into this, but it's still a pretty rare occurance.

This patch also cleans up some of the networking logic including removing a debug print that was used to diagnose LAN discovery a few months back.