dtrace based blocking http api to map local port to uid

dtrace.js

var http = require('http');
var spawn = require('child_process').spawn;
var dtrace = spawn("dtrace", ["-s", "dtrace.d", "-C"]);

var known_ports = {};
var pending_requests = {};

dtrace.stdout.on("data", function(data){
    var lines = data.toString().split("\n");
    for (i in lines) {
        line = lines[i];
        if (line === "") continue;
        var parts = line.split(" ");
        if (parts.length < 5) continue;
        var uid = parts[parts.length-4];
        var port = parts[parts.length-3];
        console.log("uid", uid, port);
        known_ports[port] = uid;
        if (pending_requests[port] !== undefined) {
	        res.end(uid);
			delete pending_requests[port];
			console.log("returned port to pending request");
		}
    };
});

dtrace.stderr.on("data", function(data){
    console.log("got error: ", data.toString());
});

dtrace.on("exit", function(data){
    console.log("got exit: ", data);
});

http.createServer(function (req, res) {
    var port = req.url.substr(1);
    console.log("requested port", port);
    res.writeHead(200, {'Content-Type': 'text/plain'});
    if (known_ports[port] !== undefined) {
        res.end(known_ports[port]);
		console.log("port is already known");
        // delete known_ports[port];
    } else {
        pending_requests[port] = res;
		console.log("port is not known, queing request");
		setTimeout(function(){
			delete pending_requests[port];
			res.end("not found");
			console.log("timing out");
		}, 1000)
    }
}).listen(1337, '127.0.0.1');