Service discovery using node.js and ssdp / universal plug n play

ssdp.node.js

var dgram = require('dgram'); // dgram is UDP

// Listen for responses
function listen(port) {
	var server = dgram.createSocket("udp4");

	server.on("message", function (msg, rinfo) {
		console.log("server got: " + msg + " from " + rinfo.address + ":" + rinfo.port);
	});

	server.bind(port); // Bind to the random port we were given when sending the message, not 1900

	// Give it a while for responses to come in
	setTimeout(function(){
		console.log("Finished waiting");
		server.close();
	},2000);
}

function search() {
	
	var message = new Buffer(
		"M-SEARCH * HTTP/1.1\r\n" +
		"HOST:239.255.255.250:1900\r\n" +
		"MAN:\"ssdp:discover\"\r\n" +
		"ST:ssdp:all\r\n" + // Essential, used by the client to specify what they want to discover, eg 'ST:ge:fridge'
		"MX:1\r\n" + // 1 second to respond (but they all respond immediately?)
		"\r\n"
	);

	var client = dgram.createSocket("udp4");
	client.bind(); // So that we get a port so we can listen before sending
	listen(client.address().port);
	client.send(message, 0, message.length, 1900, "239.255.255.250");
	client.close();
}

search();

Nice post. I had to move the "client.close" statement inside the .send callback to get this run my local PC (Windows 7). I've uploaded a listener code to listen UDP port 1900 here: https://github.com/harikandakkai/ssdp/blob/master/UPnPListener.js

Get this error:

dgram.js:323
throw errnoException(process._errno, 'getsockname')
^
Error: getsockname EINVAL

Any ideas why?

@leonbrag you need to wait for client.bind(); on line 32 to finish - put a callback inside client.bind() and run the other stuff in there.

@chr15m, thank you!