index.js

#!/usr/bin/env node
var gst = require('gstreamer-superficial');
const port = process.env.UDPPORT || 5000
const timeout = process.env.UDPTIMEOUT || 500

var pipeline = new gst.Pipeline('udpsrc name=src port='+port+' timeout='+timeout+'000000 ! application/x-rtp,media=audio,clock-rate=44100,encoding-name=L16,channels=2,payload=96 ! rtpL16depay ! audioconvert ! autoaudiosink');
var src = pipeline.findChild('src');
pipeline.pollBus((msg) => {
    if (msg.name == 'GstUDPSrcTimeout') {
        console.log(new Date, 'source timeout in port ' + src.port);
        pipeline.stop();
    }
});
pipeline.play();
console.log(new Date, 'listening on ' + port);

loop.sh

#!/bin/bash
while true; do
  UDPPORT=5000 ./index.js
  UDPPORT=5001 ./index.js
done

test1.sh

#!/bin/bash
gst-launch-1.0 audiotestsrc ! audio/x-raw,channels=2,rate=44100 ! rtpL16pay ! udpsink host=127.0.0.1 port=5000

test2.sh

#!/bin/bash
gst-launch-1.0 audiotestsrc wave=white-noise ! audio/x-raw,channels=2,rate=44100 ! rtpL16pay ! udpsink host=127.0.0.1 port=5001