rcv..js

var dgram = require('dgram'),
    vsocket = dgram.createSocket('udp4'),
    dataRcv=0, prevDataRcv=0;


setInterval(function(){
    console.log('Rcv rate',dataRcv-prevDataRcv);
    prevDataRcv = dataRcv;
},1000)


vsocket.bind(35668,'127.0.0.1',function(){
    vsocket.addMembership('224.0.0.101','127.0.0.1');
      vsocket.on('message',function(data){
        dataRcv+=data.length;
    });
});

send.js

var dgram = require('dgram'),
    socket = dgram.createSocket('udp4'),
    dataSent=0, prevdataSent= 0,
    buf = new Buffer(65507);


setInterval(function(){
    console.log('Send rate',dataSent-prevdataSent);
    prevdataSent = dataSent;
},1000)


socket.bind('127.0.0.1',function(){
    socket.addMembership('224.0.0.101','127.0.0.1');
    socket.setMulticastLoopback(false);
    function send(){
        dataSent+=buf.length;
        socket.send(buf,0,buf.length,35668,'224.0.0.101',send);
    }
    send();
});

Test of max UDP multicats rate on loopback interface.

Hey
I can't reproduce this
Suggest you look at https://github.com/hij1nx/net-log
for an initial direction on how you might want to go about this.