Having a getter for the local port of the server socket permits the
use of port 0.
While creating a ServerSocket, port 0 means the socket will use any
available port of the system. To know which port was chosen, you need
the getter added by this commit.
... so far, this can not be turned off (will do when I have
merged the recent build system changes into this branch - I am
glad that I at least have a working reference point now ;)).
unfortunately, imdiag currently does not offer many counters (to
phrase it politely). Will need to implement a counter interface as
one of the very next steps...
