Remote Procedure Calls with Socket.IO

With socket.io, we can execute a callback function over WebSockets (or a relevant alternative). The function is defined client side, yet called server side (and vice versa). This can be a very powerful way to share processing resources and functionalities between clients and servers—it's called Remote Procedure Calls (RPC).

In this recipe, we'll create a way for the server to call a client-side function that squares a number, and for the client to call a server-side function that sends a Base64 encoded (http://en.wikipedia.org/wiki/Base64) sentence back to the client.

Getting ready

We simply need to create a new folder with the new client.html and server.js files.

How to do it...

On our server, as before, we load our http module and the client.html file, create our HTTP server, and attach socket.io. Refer to the following code:

var http = require('http');
var clientHtml = require('fs').readFileSync('client.html');

var plainHttpServer = http.createServer(function...