In some parts of the code a reverse-lookup (e.g. "connection from xxx") is used.
An address-family independent reverse-lookup function is provided by this patch,
exploiting that a socket is described by {src addr, src port, dst addr, dst port}:
* host_and_port(): prints host and port number of given socket,
* local_name(): pretty-prints src-addr/src-port,
* remote_name(): pretty-prints dst-addr/dst-port;