What is the difference between socket.io client and socket.io server? Alternatives to socket.io?

Question

I have been breaking my head on understanding what exactly is socket.io and its role in the whole persistent communication between client and server in general. Some fundamental questions that keep coming up in my mind are :

• Are node.js and socket.io server different ways of doing the same thing ? Like lighthttpd and apache ?
• Why should I use socket.io server if I have node.js ?
• Can I use socket.io client with another server side programming language like PHP ?
• Are there alternatives to using socket.io client ?
• Is socket.io client just another javascript library for websocket communication ?

Thanks :)

Answer 1

The Socket.IO server accepts connections from Socket.IO clients. This is not any different than any other server (such as a web server like Apache) accepting a connection from a client (such as a web browser like Internet Explorer).

Node.js is a platform built on top of the V8 JavaScript engine, which comes with a convenient library usually used for web and network applications. Socket.IO is a web-socket-like communication wrapper and RPC which enables servers and clients to communicate over a variety of transports (every thing from long-polling JSON to real Web Sockets). Generally, the Socket.IO server code runs in your JavaScript application running on top of Node.js, and the Socket.IO client runs in your JavaScript on a web browser. (Note that you can run the Socket.IO client in your Node.js application to, which I have used in the past as a quick RPC between multiple Node.js applications.)

There are Socket.IO clients available for many languages, and yes I believe there is one for PHP but I haven't used it personally.

If you want to communicate with a Socket.IO server, you must use a Socket.IO client. It is a protocol all on its own.