In TCPConnectionMap.TCPConnection(), the following code is executed:
sock=socketFactory.createSocket(); // (1)
sock.bind(); // (2)
sock.connect(); // (3)

In the first step, an unconnected socket is created and added to the 'sockets' hashmap in DefaultSocketFactory. This is used to dump the open sockets in a JGroups program (e.g. via probe.sh socks).

However, if step (3) fails, e.g. because the destination is not reachable, the socket should be removed from the 'sockets' hashmap, but isn't !

SOLUTIUON:
#1 Check all occurrences of this or similar code and make sure exceptions don't lead to lingering sockets
#2 Make the 'sockets' hashmap a weak hashmap, so refs can be GC'ed when memory is low
#3 Store string reps of the sockets rather than the sockets themselves