Bind the socket to Address on the current machine. This
operation, together with tcp_listen/2 and tcp_accept/3 implement
the server-side of the socket interface. Address is either an
plain Port or a term HostPort. The first form binds the socket
to the given port on all interfaces, while the second only binds
to the matching interface. A typical example is below, causing
the socket to listen only on port 8080 on the local machine's
network.
tcp_bind(Socket, localhost:8080)
If Port is unbound, the system picks an arbitrary free port
and unifies Port with the selected port number. Port is
either an integer or the name of a registered service. See also
tcp_connect/4.