Poor network performance with Websockets running on apple device

Question

I am working on an HTML/Javascript running on mobile devices that is communicating with a Qt/C++ application running on a PC. Both the mobile device and the PC are on a local network. The communication between the HTML page (client) and the C++ app (server) is done using Websockets.
The HTML page is a remote control for the C++ application, so it is needed to have a low latency connection between the mobile device and the PC.
When using any non-Apple device as a client, data is sent to a rate between 60 to 120 frames/sec, which is totally acceptable. When using an Apple device, this rate falls to 3-4 frames/sec. I also checked ping times (Websocket implementation, not a ping command from command line). They are acceptable (1-5 ms) for Apple devices as long as the device is not transmitting data. Whenever it transmits data, this ping time raises to 200ms.
Looking from the Javascript side, the Apple devices always send data at a consistent rate of 60 frames/sec, as any other devices do. However, on the server side, only 3 to 4 of these 60 frames are received when the client is an Apple device.
Does anyone have any idea on what can be happening?
Here is my Javascript code :
<script language="javascript" type="text/javascript">
        var wsUri = document.URL.replace("http", "ws");
        var output;
        var websocket;
        function init()
            output = document.getElementById("output");
            wsConnect();
        function wsConnect()
            console.log("Trying connection to " + wsUri);
            try
                output = document.getElementById("output");
                websocket = new WebSocket(wsUri);
                websocket.onopen = function(evt)
                        onOpen(evt)
                websocket.onclose = function(evt)
                        onClose(evt)
                websocket.onmessage = function(evt)
                        onMessage(evt)
                websocket.onerror = function(evt)
                        onError(evt)
            catch (e)
                console.log("Exception " + e.toString());
        function onOpen(evt)
            alert("Connected to " + wsUri);
        function onClose(evt)
            alert("Disconnected");
        function onMessage(evt)
            alert('Received message : ' + evt.data);
        function onError(evt)
            alert("Error : " + evt.toString());
        function doSend(message)
            websocket.send(message);
        window.addEventListener("load", init, false);
</script>
Data is sent from Javascript side using dosend() function.

Answer 1

What version of websocket is your server using? That is pretty much on the bleeding edge of things. It looks like you need to use RFC6455 and iOS6 and it should work fine.
Thanks for the post. I didn't know about websockets. Very interesting.