Python socket module. Connecting to an HTTP proxy then performing a GET request on an external resource

Question

To begin with, I understand there are other modules such as Requests that would be better suited and simpler to use, but I want to use the socket module to better understand

Answer 1

To make a HTTP request to a proxy open a connection to the proxy server and then send a HTTP-proxy request. This request is mostly the same as the normal HTTP request, but contains the absolute URL instead of the relative URL, e.g.

 > GET http://www.google.com HTTP/1.1
 > Host: www.google.com
 > ...

 < HTTP response

To make a HTTPS request open a tunnel using the CONNECT method and then proceed inside this tunnel normally, that is do the SSL handshake and then a normal non-proxy request inside the tunnel, e.g.

 > CONNECT www.google.com:443 HTTP/1.1
 >
 < .. read response to CONNECT request, must be 200 ...

 .. establish the TLS connection inside the tunnel

 > GET / HTTP/1.1
 > Host: www.google.com

Answer 2

Python 3 requires the request to be encoded. Thus, expanding on David's original code, combined with Steffens answer, here is the solution written for Python 3:

def connectThroughProxy():
    headers = """GET http://www.example.org HTTP/1.1
                Host: www.example.org\r\n\r\n"""

    host = "192.97.215.348" #proxy server IP
    port = 8080              #proxy server port

    try:
        s = socket.socket()
        s.connect((host,port))
        s.send(headers.encode('utf-8'))
        response = s.recv(3000)
        print (response)
        s.close()
    except socket.error as m:
       print (str(m))
       s.close()
       sys.exit(1) 

This allows me to connect to the example.org host through my corporate proxy (at least for non SSL/TLS connections).