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Spy on a running node program by having a man on the inside

npm install spies

The first thing you need is to setup a spy inside your program

var spies = require('spies');
var net = require('net');
net.createServer(function(socket) {
    var spy = spies();
    spy.on('echo', function() {
    spy.on('load-avg', function() {

As you can see spy is simply a readable and writable stream so you can pipe to any kind of stream transport (like a websocket)

You can use the spies.listen helper if you just want to listen using a tcp server

spies.listen(9999, function(spy) {
    // attach commands here 

Afterwards you can use netcat to contact and debrief your spy

nc localhost 9999

This starts a repl where you can type in commands

$ : help
  : watch
  : echo
  : load-avg

help and watch are build in commands than print the help and runs the same command every 1 second. You invoke a command simply typing it and pressing enter and the result will be pretty printed below.

$ : 0.30126953125
  : 0.3203125
  : 0.33642578125

To pass arguments to the commands simply seperate them them by a space

echo hello
$ : hello