Asynchronous Handing of Socket Responses - sockets

Question

My problem is as follows: I have a TCP socket on which I asynchronously send messages based on a proprietary protocol. Upon receiving a response for a message I need to make sure that data gets sent back to the function that initially sent the message. The problem is I can only listen for responses on a "data" event on the socket (in this case in Node.js) and I have no way of easily determining which responses correspond to which messages.
Below is an example that I hope will give you an idea of what I am trying to accomplish.
function getTemperature (callback) {
socket.write(message);
// Good?
socket.on('data', callback);
}
function getVoltage (callback) {
socket.write(message);
// Other way to invoke callback?
}
getTemperature(function (err, temperature) {});
getVoltage(function (err, voltage) {});
socket.on('data', handleData function (data) {
// Somehow send data to correct function
}
One idea I had was registering multiple event handlers for the data event but this seems kind of wacky. What is the correct way to handle this?

Answer 1

When dealing with an asynchronous protocol, you would typically need to design the protocol so that each request has a unique ID that is included in the request data and gets sent back in the response. That way, you can receive responses out of order, and even receive unsolicited messages.
When you send a request, put the request ID in a list somewhere, along with a callback that will be called when the response arrives.
When you get a data event, append the raw data to a buffer, and then parse out only complete messages from the buffer, leaving incomplete messages for later completion. For each complete message parsed out, check if it has a request ID. If no, the message is unsolicited, so process it accordingly. Otherwise, look for the request ID in the list, and if found then call the callback associated with it.