emitter.js

var util = require('util'),
    EventEmitter = require('events').EventEmitter;

var Server = function() {
  var self = this;

  this.on('custom_event', function() {
    self.logSomething('custom_event');
  });

  this.logSomething('init');
};

util.inherits(Server, EventEmitter);

Server.prototype.doSomething = function() {
  this.emit('custom_event');
};

Server.prototype.logSomething = function(something) {
  console.log(something);
}

var s = new Server();
s.doSomething();