Why we need a carriage return r before the new line character n?

Question

In the following code the HTTP protocol needs two newline character but what is the need of the r there. Why can’t we just add two n and send the request?

import socket
mysock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
mysock.connect(("data.pr4e.org",80))
cmd = 'GET http://data.pr4e.org/romeo.txt HTTP/1.0rnrn'.encode() # here
mysock.send(cmd)
while True:
    data = mysock.recv(512)
    if len(data) > 0:
        print(data.decode())
    else :
        break
mysock.close()

Asked By: Chetan Naik

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Source

Answer 1

Because that’s how the HTTP protocol is defined. More specifically, HTTP 1.0 defines a request like this:

Request        = Simple-Request | Full-Request

Full-Request   = Request-Line             
                 *( General-Header       
                  | Request-Header      
                  | Entity-Header )    
                 CRLF
                 [ Entity-Body ]
 
Request-Line = Method SP Request-URI SP HTTP-Version CRLF

Full-Request, which is what should be used by any HTTP 1.0 compatible client (simple request is HTTP 0.9 and deprecated) needs to have two CRLF tokens (one is in Request-Line). A CRLF token is the two bytes rn. Hence the need to end the string in your example with rnrn.

This design choice was kept in HTTP 1.1.

Answered By: Marco Bonelli

Answer 2

Because that is how the HTTP protocol works.

The request/status line and headers must all end with <CR><LF> (that is, a carriage return followed by a line feed). The empty line must consist of only <CR><LF> and no other whitespace.

https://en.wikipedia.org/wiki/HTTP_message_body

Answered By: Tejas Sarade

Why we need a carriage return r before the new line character n?

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