Connecting to HTML5 Websocket

Question

I'm a bit confused about HTML5 Websockets. I've looked at numerous tutorials out there and a lot of them have different variations of connecting using different ports. What do these ports mean?

Adobe for instance, uses this:

new WebSocket('ws://localhost:1740');

Then another tutorial has this where no ports are required:

new WebSocket("ws://www.websockets.org");

And finally a third tutorial has a port, but it's completely different:

new WebSocket("ws://localhost:8080/echo");

My question would be, why do these vary? How do I know which ports to connect to? Also, I've attempted to do my own connection:

var ws = new WebSocket("ws://test.ontarget-network.com/");

But I get the following error: Unexpected response code: 200

I've tested around and tried connecting to various other "ports" (not knowing what I'm doing obviously, typing in random numbers) and this error would disappear, however, my code

ws.onopen = function(){
   alert("Connection Established");
};

would not execute.

I'm trying to fully understand HTML5's Websockets API so I can experiment and create more dynamic applications. Thanks for the help.

Answer 1

The following comes from the latest WebSocket draft:

By default the WebSocket protocol uses port 80 for regular WebSocket connections and port 443 for WebSocket connections tunneled over TLS [RFC2818].

Really though, you should be able to use any valid port not in use. As long as clients are trying to connect to the same port that the server-side script opens for the socket connection, you should be fine.

A quick note on ports:

• Port 80 is the HTTP port.
• Port 8080 is the alternate HTTP port.
• Port 443 is the HTTPS (i.e., HTTP with TLS) port.
• Port 1740 in the Adobe code seems like some random port not already in use by other services.

For a full list of preset ports, please see the following:
http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers

As for your "Unexpected response code: 200" error, I'm guessing that the WebSocket URL you're using on the client side is not pointing to a valid server-side script, but that's hard to comment on without more info.

Answer 2

The server should have an endpoint that accepts WebSocket connections. So, if that endpoint is /echo you would want to connect to:

ws://localhost:8080/echo/websocket

You will get the Unexpected response code: 200 error if you exclude the /websocket suffix after the endpoint. I was having the same confusion and this link cleared things up a bit for me.