What, at the bare minimum, is required for an HTTP request?

Question

I'm trying to issue a GET command to my local server using netcat by doing the following:

echo -e "GET / HTTP/1.1\nHost: localhost" | nc localhost 80 

Unfortunately, I get a HTTP/1.1 400 Bad Request response for this. What, at the very minimum, is required for a HTTP request?

Answer 1

if the request is: "GET / HTTP/1.0\r\n\r\n" then the response contains header as well as body, and the connection closes after the response.

if the request is:"GET / HTTP/1.1\r\nHost: host:port\r\nConnection: close\r\n\r\n" then the response contains header as well as body, and the connection closes after the response.

if the request is:"GET / HTTP/1.1\r\nHost: host:port\r\n\r\n" then the response contains header as well as body, and the connection will not close even after the response.

if your request is: "GET /\r\n\r\n" then the response contains no header and only body, and the connection closes after the response.

if your request is: "HEAD / HTTP/1.0\r\n\r\n" then the response contains only header and no body, and the connection closes after the response.

if the request is: "HEAD / HTTP/1.1\r\nHost: host:port\r\nConnection: close\r\n\r\n" then the response contains only header and no body, and the connection closes after the response.

if the request is: "HEAD / HTTP/1.1\r\nHost: host:port\r\n\r\n" then the response contains only header and no body, and the connection will not close after the response.

Answer 2

It must use CRLF line endings, and it must end in \r\n\r\n, i.e. a blank line. This is what I use:

printf 'GET / HTTP/1.1\r\nHost: www.example.com\r\nConnection: close\r\n\r\n' |   nc www.example.com 80 

Additionally, I prefer printf over echo, and I add an extra header to have the server close the connection, but those aren’t needed.