http.createserver vs net.createserver in node.js

http.createServer() sets up a server that handles the HTTP protocol, which is indeed transmitted over tcp. net.createServer() creates a server that simply understands when a TCP connection has happened, and data has been transmitted, and so on, but doesn't know anything about whether a valid HTTP request has been received, etc.

If you are writing a web server, favor http.createServer() over net.createServer() as it will save you a lot of work. If you are writing some other kind of server, do not use http.createServer().

Straight from the Node Net documentation. NET is the basic bare-bones server you can create. It's particularly useful for setting up a cluster of servers and allows simple connections but on that you'll want communication protocols, namely HTTP, which HTTP is in fact a NET server at it's core.

The net module provides an asynchronous network API for creating stream-based TCP or IPC servers (net.createServer()) and clients (net.createConnection()).

And from the HTTP documentation. HTTP is the common way to transmit large sets of data as requested by the client and then a response is generated. It's the standard way of communicating over the internet and introduces the concept of handshakes and is done through REST protocol, you know the usual request and response way of communicating.

The HTTP interfaces in Node.js are designed to support many features of the protocol which have been traditionally difficult to use. In particular, large, possibly chunk-encoded, messages. The interface is careful to never buffer entire requests or responses — the user is able to stream data.

Websockets are an upgrade over the HTTP headers and offer low latency and less server load and are a much more minimal conversation. If you're talking peer to peer communication, that's the way you'll want to go.

I don't know much of a Node.js, but I know something about networks. HTTP is a protocol that works on 7th (Application) layer of model OSI. TCP is protocol that works on 4th (Transport) layer of model OSI. As you said, yes HTTP works on top of the TCP. The option of creating HTTP server by http.createServer() is there so you don't have to implement it by yourself by using net.createServer(). The protocol TCP might by used by lot of applications, you might create your own, or implement some different protocol than HTTP, for example: FTP, DNS, SMTP, Telnet and much much more.