Returns the address of the socket at the other side of the connection.
The socket must be connected, which implies it has executed a successful socket->connect
(client) or is a cloned socket from a socket in socket->listen
mode (server, see socket<-clients and socket->accept_message).
If the socket is in the Unix socket<-domain,
the return value is a name describing the file (which will be the same
as the absolute
path-name of the file used to create the
socket).
If the socket is in the inet socket<-domain,
the return value is a
tuple object holding a
name describing the internet address of the socket at the other end in
decimal numeric notation and an integer describing the port.
