Websocket connection setup takes a relatively long time - is this normal?

Question

It seems to be taking about 1 second to set up a websocket connection when the client and server are both running locally on my machine. This seems like quite a long time to me - is it? Could anyone compare this with their own experiences?

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Details:

I have a websocket request like this on the client (Chrome 25, Windows7 64):

this.ws = new WebSocket('ws://' + host + ':' + port);

On the server side I have Node with ExpressJS running and einaros/ws handling the upgrade and WS connection.

I'm timing on the client, from just before the new WebSocket() to the ws.onopen event.

Answer 1

I found a clear answer to this question. Apparently, using localhost causes the browser to try to connect to ipv6 first then fallback to ipv4 after a 1 second timeout. The problem is solved by using 127.0.0.1 because it will try to connect using ipv4 in the first place.

Source

Answer 2

That is not normal.

I am using Chrome 24 on Ubuntu with the following test code (just fire up Chrome Dev console and paste it in):

function test_ws(uri){
    start = new Date().getTime(); 
    ws = new WebSocket(uri);
    ws.onopen = function(){
        console.log("onopen of", uri, "in", (new Date().getTime() - start), "ms");
    };
}

Here are some average results I've gotten for various values of uri:

• ws://localhost:6080: 20 ms (custom python based WebSocket server)
• ws://localhost:6090: 3 ms (custom node.js + einaros/ws based WebSocket server)
• ws://echo.websocket.org: 130 ms
• wss://echo.websocket.org: 190 ms

So even using an encrypted connection to a public remote Websocket server is still less than one fifth of a second on average until the open event. The maximum time I saw was 250ms. For a local connection, the delay should really only be a few milliseconds.

My guess would be that you server setup is doing a bunch of processing before accepting the connection. Perhaps you are initializing a bunch of client data in the new connection handler?

Update:

Here is a simple einaros/ws based WebSocket server that gives 3 ms onopen response using the client test code above:

var WebSocketServer = require('ws').Server
  , wss = new WebSocketServer({port: 6090});
wss.on('connection', function(ws) {
    console.log("got connection");
});