It’s a well know fact that you can preform HTTP requests with CURL. Zend Framework does the same job with Zend_Http. Especially Zend_Http_Client can be used to “replace” the usual client – the browser, and to perform some basic requests.

I’ve seen mostly GET requests, although Zend_Http_Client can perform various requests such as POST as well.

// new HTTP request to some HTTP address
$httpClient = new Zend_Http_Client('http://www.example.com/');
// GET the response
$response = $httpClient->request(Zend_Http_Client::GET);

Here’s a little snippet showing how to POST some data to a server.

// new HTTP request to some HTTP address
$client = new Zend_Http_Client('http://www.example.com/');
// set some parameters
$client->setParameterPost('name', 'value');
// POST request
$response = $client->request(Zend_Http_Client::POST);

Note that the request method returns a response. Thus if you are simulating a form submit action you can “redirect” to the desired page just like the form.

// new HTTP request to some HTTP address
$client = new Zend_Http_Client('http://www.example.com/');
// set some parameters
$client->setParameterPost('name', 'value');
// POST request
$response = $client->request(Zend_Http_Client::POST);
echo $response->location;

After Node.js is istalled, described in my previous post, I can simply run this command:

stoimenpopov:~# node server.js

and this will start the server with the code within server.js. But what’s the code of server.js?

Following the instructions of Node’s homepage and most of the tutorials I’ve found, I can simply copy/paste the code from the first lines of Node’s page:

var http = require('http');
http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(8124, "127.0.0.1");
console.log('Server running at http://127.0.0.1:8124/');

There are several things I find interesting in this code, making it different from JavaScript as we know it. First of all what is

var http = require(‘http’)

and why I need it? What is the purpouse of 8124 and 127.0.0.1?

Node is built in modules and to use one of them you must first include it with require. Just like the example above with require(‘http’). In the same manner you can include every module of Node.

What are the Node’s modules are pretty well described in the API page. Well I’d like to say that the API page is quite insufficient. That is very bad, cause most of the code you’ll need developing a node.js applicatoin isn’t described/explained there.

However is more than obvious that 8124 is the port, while 127.0.0.1 is the IP address of the server, which in this case is the localhost. Thus after running the server and typing http://127.0.0.1:8124/ into your browser you’ll get “Hello World”. This is not enough when the server is running on a remote machine, while you’ve to access it from your local computer.

The first server

As I described the code above shows you an example server. In fact the API page shows a slightly different code:

var http = require('http');

http.createServer(function (request, response) {
  response.writeHead(200, {'Content-Type': 'text/plain'});
  response.end('Hello World\n');
}).listen(8124);

console.log('Server running at http://127.0.0.1:8124/');

Here the line:

}).listen(8124);

omits the address of the server. It appears to be non-required and the server is supposed to listen on this machine on the given port. To be honest I’m not sure why you’ve to write the server address, except for limit the possible address to this one. However in my case the server was installed on a remote machine indeed, while I was trying to access it from my local machine. So here are some base steps to do before accomplishing this.

1. Changing the IP address

First of all you can omit the IP address. This can help you move the code from one server to another without changing the code.

}).listen(8124, ip_address);

possibly a better solution is:

}).listen(8124);

Node can listen on whatever port you say so this is up to you to decide which port should be opened.

2. Opening the port

While everything’s on the localhost you wont have problems with port opening. If you’d like to access it remotely however, you’ve to open the port. In other words http://127.0.0.1:8124/ is OK without port opening, but http://example.com:8124/ – is not!

To open a port in UNIX/Linux you’ve to type this command in the terminal:

iptables -A INPUT -p tcp --dport 8124 -j ACCEPT

don’t forget to change the port number from 8124 to whatever port number you’re using.

3. The first AJAX call

We still cannot make the first AJAX call to the Node server. Here I’m using jQuery because of the easy AJAX interface.

$(document).ready(function() {
	$.ajax({
    	// setup the server address
        url : 'http://example:8124/',
        success : function(response) {
        	// on success
        	alert(response);
		},
        error : function() {
        	// on error
        }
    });
});

After executing this code in a browser there wont be a response. That is because of the remote AJAX calls restriction. To overcome this you’ve to change the returned header from the Node’s server, by adding this:

'Access-Control-Allow-Origin' : '*'

Now server.js will look like this:

var http = require('http');

http.createServer(function (request, response) {
	response.writeHead(200, {
		'Content-Type': 'text/plain',
		'Access-Control-Allow-Origin' : '*'
	});
	response.end('Hello World\n');
}).listen(8124);

you can now either load http://example.com:8124/ into your browser or to make the AJAX call. In both cases the answer will be “Hello World”

Summary

Now you have a very simple Node.js server. Well it is nothing special as it responses with “Hello World” on every request, but it works remotely.

Soon I’ll describe how to change the server so it can waits to respond until some event is emitted – which is the real power of Node.js.

$httpClient = new Zend_Http_Client('http://..../');
// request via post
$response = $httpClient->request(Zend_Http_Client::POST);
// or get
$response = $httpClient->request(Zend_Http_Client::GET);

However the interesting and useful thing is that you can perform authenticated requests:

$httpClient = new Zend_Http_Client('http://username:password@example.com/');
// or define it later
$httpClient = new Zend_Http_Client('http://example.com/');
$httpClient->setAuth('username', 'password');

That’s an opportunity to send/receive authenticated POST requests.

$httpClient = new Zend_Http_Client('http://username:password@example.com/');
// now post
$httpClient->request(Zend_Http_Client::POST);

This is a common task. You’d like to know whether the image on the remote server exists. Zend Framework gives the answer of this question and in particular this can be completed with Zend_Http_Client.

Content-Type and Content-Length

The little problem is that checking for content-type is not always correct, because it will return an image content type even when the image does not exists, so it’s better to check for content-length.

Code

The simple way to check this is like that:

$client = new Zend_Http_Client('http://remote-machine/image.jpg');
$response = $client->request('head');
if ( NULL == $response->getHeader('Content-Length') )
    // do whatever if the image does not exists.

In fact here, in this example I don’t check for GET request, because is way to slow than the HEAD method, but you should be aware of incorrect responses when using HEAD. In fact if you request the HEAD of a FLV video it will be returned text content-type, while using GET everything’s working fine but slow though.