Building the server

In this article we'll set up the server for our phone app. The server file will look like a regular Express server file with one difference, the Peer server.

First of all, create a file called server.js in the same location as the HTML and CSS files you created previously. This is the entry point of our app, as defined in our package.json file.
You'll need to start your code by requiring the peer server at the top of the server.js file, to ensure that we have access to the peer server:
js
```
const { ExpressPeerServer } = require("peer");
```
You then need to actually create the peer server. Add the following code below your previous line:
js
```
const peerServer = ExpressPeerServer(server, {
  proxied: true,
  debug: true,
  path: "/myapp",
  ssl: {},
});
```
We use the ExpressPeerServer object to create the peer server, passing it some options in the process. The peer server will handle the signalling required for WebRTC for us, so we don't have to worry about STUN/TURN servers or other protocols.

Finally, you'll need to tell your app to use the peerServer by calling app.use(peerServer). Your finished server.js should include the other necessary dependencies you'd include in a server file, as well as serving the index.html file to the root path. Update server.js so that it looks like this:

const express = require("express");
const http = require("http");
const path = require("path");
const app = express();
const server = http.createServer(app);
const { ExpressPeerServer } = require("peer");
const port = process.env.PORT || "8000";

const peerServer = ExpressPeerServer(server, {
  proxied: true,
  debug: true,
  path: "/myapp",
  ssl: {},
});

app.use(peerServer);

app.use(express.static(path.join(__dirname)));

app.get("/", (request, response) => {
  response.sendFile(`${__dirname}/index.html`);
});

server.listen(port);
console.log(`Listening on: ${port}`);

You should be able to connect to your app via localhost (in our server.js we're using port 8000 (defined on line 7) but you may be using another port number). Run yarn start (where start refers to the script you declared in package.json on the previous page) in your terminal. Visit localhost:8000 in your browser and you should see a page that looks like this:

If you want to learn more about Peer.js, check out the Peer.js Server repo on GitHub.