How to know when all data has arrived in node sockets

I'm using node.js with the net module on my backend and flash on my frontend. I want to pass objects with json format. How would I know when all data has arrived in my backend so I can then do a JSON.parse?

My actionscript:

var obj = new Object();
obj.msg = "I want pizza";
xmlSocket.send(JSON.encode(obj));

My javascript:

    socket.on("data", function(data){
        var msg = JSON.parse(data.toString());

        var i = 0;
        while(i < clientData.length){

            var client = clientData[i];
            if(client.writable){
                client.write(msg.msg, 'utf8');
            }
            i++;    
        }

});

At the moment I'm getting an error, which I'm not sure has to do with this since it displays the whole object:

undefined:1
{"msg":"I want pizza"}
                      ^
SyntaxError: Unexpected token