Quick and dirty AES67/Dante SAP/SDP Discovery Service. Change sdpConfig and addr accordingly

aes67_sdp.js

var dgram = require('dgram');
var socket = dgram.createSocket({ type: 'udp4', reuseAddr: true });

const PORT = 9875;
const MULTICAST_ADDR = '239.255.255.255';

//options, need to be changed
var addr = '127.0.0.1';
var multicastAddr = '239.69.0.119';

socket.bind(PORT, function(){
	socket.setMulticastInterface(addr);
});

var constructSDPMsg = function(){
	var sapHeader = Buffer.alloc(8);
	var sapContentType = Buffer.from('application/sdp\0');
	var ip = addr.split('.');

	//write version/options
	sapHeader.writeUInt8(0x20);

	//write hash
	sapHeader.writeUInt16LE(0xefef, 2);

	//write ip
	sapHeader.writeUInt8(parseInt(ip[0]), 4);
	sapHeader.writeUInt8(parseInt(ip[1]), 5);
	sapHeader.writeUInt8(parseInt(ip[2]), 6);
	sapHeader.writeUInt8(parseInt(ip[3]), 7);

	var sdpConfig = [
		'v=0',
		'o=- 10 0 IN IP4 '+addr,
		's=Name',
		'c=IN IP4 '+multicastAddr+'/15',
		't=0 0',
		'a=clock-domain:PTPv2 0',
		'm=audio 5004 RTP/AVP 98',
		'c=IN IP4 '+multicastAddr+'/15',
		'a=rtpmap:98 L24/48000/2',
		'a=source-filter: incl IN IP4 '+multicastAddr+' '+addr,
		'a=sync-time:0',
		'a=framecount:128',
		'a=ptime:1',
		'a=mediaclk:direct=0',
		'a=ts-refclk:ptp=IEEE1588-2008:00-00-00-00-00-00-00-00:0',
		'a=recvonly',
		''
	];

	var sdpBody = Buffer.from(sdpConfig.join('\r\n'));

	return Buffer.concat([sapHeader, sapContentType, sdpBody]);
}

var sendSDPMsg = function(){
	var sdpBuf = constructSDPMsg();
	socket.send(sdpBuf, PORT, MULTICAST_ADDR, function(err){});
}

sendSDPMsg();
setInterval(function(){
	sendSDPMsg();
}, 30*1000);