lsof.js

var cluster = require('cluster');
var http = require('http');
var cp = require('child_process');

if (cluster.isMaster) {
    var worker = cluster.fork();
} 
else {
    server = http.createServer(); // number of servers is arbitrary
    server2 = http.createServer();
    server.listen(10011, 'localhost')
    server2.listen(10012, 'localhost')
    setTimeout(run, 100); // need this timeout to recreate
}

function run() {
    var sleep = cp.spawn('sleep', ['7']);
    var lsof = cp.spawn('lsof', ['-p', sleep.pid]); 
    var grep = cp.spawn('grep', ['LISTEN']);

    lsof.stdout.on('data', function(data) {
        grep.stdin.write(data);
    });
    lsof.on('close', function() {
        grep.stdin.end();
    });

    grep.stdout.on('data', function(data) {
        console.log(data.toString());
    });
}

output is (roughly)

sleep 46028 dstibrany 11u IPv4 0x28b8ad9c32befc2d 0t0 TCP localhost:10011 (LISTEN)
sleep 46028 dstibrany 13u IPv4 0x28b8ad9c350db37d 0t0 TCP localhost:10012 (LISTEN)