Static Version

Hello Node!

In programming literature it has become the standard to create a hello world program as the first example. This article will go through a few simple hello world type examples with everything from simple terminal output to an http server that uses an external framework for some semantic sugar.

Then we'll shift gears and go through a real example that teaches enough to get you up on your feet writing your own web application using node.JS.

Hello World Examples

Here are four simple hello world examples. The comments in the code explain how the code works and the text around it explain what it does and how to test it.

Hello Console

This example is about as plain as it can get. It prints the words "Hello World" to the terminal.

hello-console.js
// Load the sys module since we want to write to the terminal
var sys = require('sys');

// Call the puts function on the sys module.
sys
.puts("Hello World");

You can run this by putting it in a file called "hello-console.js" and running it with node hello-console.js

Hello HTTP

I'd guess that while it's not the only use case for node.JS, most people are using it as a web application platform. So the next example will be a simple HTTP server that responds to every request with the plain text message "Hello World"

hello-http.js
// Load the sys module for console writing.
var sys = require('sys');
// Load the http module to create an http server.
var http = require('http');

// Configure our HTTP server to respond with Hello World to all requests.
var server = http.createServer(function (request, response) {
  response
.writeHead(200, {"Content-Type": "text/plain"});
  response
.write("Hello World\n");
  response
.close();
});

// Listen on port 8000, IP defaults to 127.0.0.1
server
.listen(8000);

// Put a friendly message on the terminal
sys
.puts("Server running at http://127.0.0.1:8000/");

Hello TCP

Node also makes an excellent TCP server, and here is an example that responds to all TCP connections with the message "Hello World" and then closes the connection.

hello-tcp.js
// Load the sys module for console writing.
var sys = require('sys');
// Load the net module to create a tcp server.
var net = require('net');

// Setup a tcp server
var server = net.createServer(function (socket) {

 
// Every time someone connects, tell them hello and then close the connection.
  socket
.addListener("connect", function () {
    sys
.puts("Connection from " + socket.remoteAddress);
    socket
.write("Hello World\n");
    socket
.end();
 
});

});

// Fire up the server bound to port 7000 on localhost
server
.listen(7000, "localhost");

// Put a friendly message on the terminal
sys
.puts("TCP server listening on port 7000 at localhost.");

Hello Router

Often you won't be using the node built-in libraries because they are designed to be very low level. This makes node quick, nimble, and easy to maintain, but is usually not enough to get started on a real world application. My first node framework is node-router. This example shows an HTTP server that responds with "Hello World" to all requests to "/" and responds with a 404 error to everything else.

hello-router.js
// Load the node-router library by creationix
var server = require('node-router').getServer();

// Configure our HTTP server to respond with Hello World the root request
server
.get("/", function (request, response) {
  response
.simpleText(200, "Hello World!");
});

// Listen on port 8080 on localhost
server
.listen(8000, "localhost");

In order to test this, you will need to install the node-router library. There are two ways to do this. You can either install it into a path that node recognizes (I create a symlink into ~/.node_libraries) or put the node-router.js file in your application and reference it locally. See the node docs on modules for more details on how modules work.

Installing Libraries

I'll install the following libraries that are common to my projects:

  • node-router - Wraps the built-in http library with many convenience functions like request routing and message body decoding.
  • haml-js - Template engine that compiles HAML templates into HTML
  • proto - Baby library that adds some useful stuff to Object.prototype

You can install these however you please, but here is how I'd do it. The following code will clone the four libraries and install them into your local node library search path:

install.sh
mkdir ~/NodeLibs
cd ~/
NodeLibs
git clone git
://github.com/creationix/node-router.git
git clone git
://github.com/creationix/haml-js.git
git clone git
://github.com/creationix/proto.git
mkdir
~/.node_libraries
cd ~/
.node_libraries
ln
-s ~/NodeLibs/*/lib/* ./

That's it for now, this article was going to explain more, but it seems it got lost and fell through the cracks. Hopefully this will help you get started working with node.JS, it's a blast!.


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