Synchronous request with Websockets

Question

I can send and receive messages from server on websockets. I need to write a function that will send data to the server and is awaiting a response from the server and then r

Answer 1

There's a neat way I used in some online game a while ago, but you will need to change stuff on the server side as well !

1st make a function to send the data

var socketQueueId = 0;
var socketQueue = {};

function sendData(data, onReturnFunction){
    socketQueueId++;
    if (typeof(returnFunc) == 'function'){
        // the 'i_' prefix is a good way to force string indices, believe me you'll want that in case your server side doesn't care and mixes both like PHP might do
        socketQueue['i_'+socketQueueId] = onReturnFunction;
    }
    jsonData = JSON.stringify({'cmd_id':socketQueueId, 'json_data':data});
    try{
        webSocket.send(jsonData);
        console.log('Sent');
    }catch(e){
        console.log('Sending failed ... .disconnected failed');
    }
}

Then in the server side, when processing the request, you should send the cmd_id back to the client with the response

webSocket.onmessage = function(e) {

    try{
        data = JSON.parse(e.data);
    }catch(er){
        console.log('socket parse error: '+e.data);
    }

    if (typeof(data['cmd_id']) != 'undefined' && typeof(socketQueue['i_'+data['cmd_id']]) == 'function'){
        execFunc = socketQueue['i_'+data['cmd_id']];
        execFunc(data['result']);
        delete socketQueue['i_'+data['cmd_id']]; // to free up memory.. and it is IMPORTANT thanks  Le Droid for the reminder
        return;
    }else{
        socketRecieveData(e.data);
    }
}

and create a function to handle all other types of returns:

socketRecieveData(data){
    //whatever processing you might need
}

so now simply if you want to send some data for the server and wait for response for that specific data you simple do:

sendData('man whats 1+1', function(data){console.log('server response:');console.log(data);});