Printing messages to the console isn't all that exciting. Let's do what Node.js was designed to do, and write a program that writes out via HTTP. Create a new file called http.server.js and put the following code into it:

After you run this program, you'll notice that it doesn't exit right away. That's because a Node.js program always runs until it's certain that no further events are possible. In this case, the open HTTP server is the source of events that will keep things going.

Testing the server is as simple as opening a new browser tab, and navigating to the hostname and port your provided in the listen() method. As expected, you should see a response that reads: Hello, HTTP!.

Let's have a closer look at the steps involved in our little program. In the first line, we include the HTTP core module and assign it to a variable called http.

Next, we create a variable called server by calling http.createServer(). The argument passed into this call is a closure that is called whenever an HTTP request comes in.

Finally, we call server.listen() to tell Node.js the port on which we want our server to run.

When you point your browser to the server, the connection closure is invoked with a req and res object. The req is a readable stream that emits 'data' events for each incoming piece of data (like a form submission or file upload). The res object is a writable stream that is used to send data back to the client. In our case, we are simply sending a 200 OK header, as well as the body Hello, HTTP!.