http.createserver vs net.createserver in node.js

问题:

I am having trouble understanding the difference between net.createserver and http.createserver in node.js.

I have read the documentation for both methods located at these two urls https://nodejs.org/api/net.html#/net_net, https://nodejs.org/api/http.html#/http_class_http_server.

I understand that http.createserver creates an http server. However, the documentation says that net.createserver creates a tcp server. I understand that tcp is the transmission protocol that http is on top of and that http servers are set up to read http request headers. I also understand the concept of even emitters in node.js pretty well. However, I don't understand this notion of a tcp server and why one would be made in node.js. The context is I am coding a chat application example in the "node.js in action" book.

回答1:

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().

回答2:

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.