The first thing we need to do is build our server. You will always need to build a server when writing back-end code. A server can be built in pure Node.js, but Express gives us simpler syntax to work with.
Servers are computer programs that receive requests from other programs, the clients and send back a response e.g share data, information or hardware and software resources.
A server is a computer program. Its job is to send and receive data.
Let's take a website for example. A website is just a collection of HTML and CSS files, images, maybe some javascript files. When you type a website address in your browser's address bar, the browser (client) sends a request to the server that lives at that address. The browser asks the server to give it the files it needs to display the website properly.
Let's build our server! Before we do anything, let's create a new file called server.js. This is where all our server code is going to live.
We already installed Express in Step 2, but we need to make sure it is included in this file specifically so we can make use of its methods. In Node.js, when you want to access the functionality of a library or module in another file, you require it.
To import Express, write the following inside server.js:
var express = require('express');To initialise our server, we just need to call the express() function. This will create an Express application for us to work with.
Add the second line of code to your server.js file:
var express = require('express');
var app = express();One more step left, we need to set a port for our server to listen to. Think of a port as a door number; any requests that come to the server will come via that door. Setting a port will allow us to find where our server is running.
We use the app.listen method to do this. This method takes two arguments: a port and a callback function telling it what to do once the server is running. Need clarification? Read more about the app.listen method in the Express documentation.
We're going to run our server on port 3000 (8080 if you are using cloud9), and run a simple console.log as our callback function. Update your server.js file, calling the app.listen method as follows:
if you are using a local environment:
var express = require('express');
var app = express();
app.listen(3000, function () {
console.log('Server is listening on port 3000. Ready to accept requests!');
});And if you are using cloud9:
var express = require('express');
var app = express();
app.listen(8080, function () {
console.log('Server is listening on port 8080. Ready to accept requests!');
});You've built your server, but it isn't running yet.
if you are using a local environment:
We need to run a command in the terminal to do this. We are going to use the node keyword to run the server file.
Type the following command in your terminal (or the cloud9 terminal):
$ node server.js
if you are using cloud9, you can also select the file server.js in the workspace folder tree and click the Run button on the top menu.
If you see this, congratulations! 👏 👏 You have built yourself a server!
| Keyword | Explanation |
|---|---|
| server | A web server is a software application which handles HTTP requests sent by the client, like web browsers, and returns web pages and information in response. |
| client | A client requests services and information from the server. Typically, a client is a computer application, such as a web browser. |
| request | A request is the message sent via HTTP from the client to the server, asking for information. |
| response | A response is the data sent back to the client from the server after an HTTP request is made. |
require() |
Require is used in Node.js to import functionality from another file or an external module. |
| module | A module is a bit of reusable code, written by you or someone else, that can be imported into a Node.js project using require. |
| method | Method is another name for a function. |
| port | A port is a number that serves as an endpoint, determining where you can access your web application. |