Fix documentation for server implementation

[Bruce-Hopkins]

I noticed two issues with the server code example:

1. The documentation for the server implementation includes the line server.ws

But in documentation, we don't console.log the port like we do HTTP and UTP:

server.on('listening', function () {
  // fired when all requested servers are listening
  console.log('listening on http port:' + server.http.address().port)
  console.log('listening on udp port:' + server.udp.address().port)
})

2. The three variables being used on the server.listen() function are not defined.

server.listen(port, hostname, onlistening)

Can I add these to the doc?