Add lag in both directions to tcp connection

slowproxy.js

// Generic TCP proxy that adds delay on packets in both directions                                                                                                          
var net  = require('net'),                                                                                                                                                  
    repl = require('repl'),                                                                                                                                                 
    sys  = require('sys');                                                                                                                                                  
                                                                                                                                                                            
var listenPort = 19999,                                                                                                                                                     
    fwdPort    = 9999;                                                                                                                                                      
                                                                                                                                                                            
var delayMs = 100;                                                                                                                                                          
var activeConns = 0;                                                                                                                                                        
var server;                                                                                                                                                                 
                                                                                                                                                                            
function delay(d) {                                                                                                                                                         
    if(!d && d!==0) {                                                                                                                                                       
        console.log("Delay is: ",delayMs,"ms");                                                                                                                             
        return;                                                                                                                                                             
    }                                                                                                                                                                       
    delayMs = d;
    console.log("Set delay to: ",delayMs,"ms");
}

var rpl = repl.start("slowproxy> ");
rpl.context.delay = delay;

server = net.createServer(function(listenSock) {
    var fwdSock;
    function closer() {
        activeConns --;
        fwdSock.end();
        listenSock.end();
    }
    listenSock.on('connect', function() {
        fwdSock = net.createConnection(fwdPort);
        fwdSock.on('connect', function() {
            activeConns ++;
            console.log("Active connections: ",activeConns);
        });
        fwdSock.on('data', function(data) {
            setTimeout(function() {
                listenSock.write(data);
            }, delayMs);
        });
    });
    listenSock.on('data', function(data) {
        setTimeout(function() {
            try {
                fwdSock.write(data);
            } catch (e) {
                closer();
            }
        }, delayMs);
    });
    listenSock.on('close', closer);
});

server.listen(listenPort);
console.log("Listening on ", listenPort, " ---> ", fwdPort, " [delay: ", delayMs,"ms]");