demo.py

import httpy

req = httpy.get('http://httpbin.org/robots.txt')

req.status # => 200
req.data # => 'User-agent: *\nDisallow: /deny'

httpy.py

from parsers import parse_url, parse_response
from request_helper import get as raw_get

class Result:
    def __init__(self, status, data):
        self.status = status
        self.data = data

def get(url):
    return Result(*parse_response(raw_get(*parse_url(url))))

parsers.py

import pyparsing as pp

def parse_url(url):
    """Pase url based on this format:

    http://[host[:port]]path[?query][#fragment]

    >>> parse_url('http://httpbin.org/')
    ('httpbin.org', 80, '/')
    >>> parse_url('http://httpbin.org/robots.txt')
    ('httpbin.org', 80, '/robots.txt')
    >>> parse_url('http://test:1234/lorem?a=b#c')
    ('test', 1234, '/lorem?a=b')
    >>> parse_url('https://mhasbini.com/')
    Traceback (most recent call last):
        ...
    ValueError: Invalid URL
    >>> parse_url('httpmhasbini.com')
    Traceback (most recent call last):
        ...
    ValueError: Invalid URL
    """

    host_pp = pp.Word(pp.alphanums + '.' + pp.alphas).setResultsName('host')
    port_pp = pp.pyparsing_common.signed_integer.setResultsName('port')
    path_pp = pp.Combine('/' + pp.Optional(pp.Word(pp.srange("[a-zA-Z0-9.-_~!$&'()*+,;=:@]")))).setResultsName('path')
    fragment_pp = pp.Optional('#' + pp.Word(pp.srange("[a-zA-Z0-9/?"))).setResultsName('fragment')

    syntax_pp = 'http://' + host_pp + pp.Optional(':' + port_pp) + path_pp + fragment_pp

    try:
        result = syntax_pp.parseString(url)        
    except pp.ParseException:
        raise ValueError('Invalid URL')

    return result.get('host'), result.get('port', 80), result.get('path')

def parse_response(raw_response):
    """Parse raw http response and return status code and body.

    >>> parse_response('HTTP/1.1 200 OK\\r\\nDate: Thu, 05 Nov 2020 03:22:48 GMT\\r\\nContent-Type: text/plain\\r\\nContent-Length: 30\\r\\nConnection: close\\r\\nServer: gunicorn/19.9.0\\r\\nAccess-Control-Allow-Origin: *\\r\\nAccess-Control-Allow-Credentials: true\\r\\n\\r\\nUser-agent: *\\nDisallow: /deny\\n')
    (200, 'User-agent: *\\nDisallow: /deny')
    >>> parse_response('lorem ipsum')
    Traceback (most recent call last):
        ...
    ValueError: Invalid raw response
    """

    DELIMITER = '\r\n\r\n'

    status_pp = pp.pyparsing_common.signed_integer.setResultsName('status')
    body_pp = pp.SkipTo(pp.Regex(r'$')).setResultsName('body')

    response_pp = pp.LineStart() + 'HTTP/1.1' + status_pp + pp.SkipTo(DELIMITER) + body_pp + pp.LineEnd()

    try:
        result = response_pp.parseString(raw_response)
    except pp.ParseException:
        raise ValueError('Invalid raw response')

    return result.get('status'), result.get('body')

request_helper.py

import socket

class ConnectionError(OSError):
    """Raised when a socket connection fail for any reason"""
    pass

def get(host, port, path):
    """Open connection and send GET HTTP request and return raw response

    >>> get('httpbin.org', 80, '/robots.txt') # doctest:+ELLIPSIS
    'HTTP/1.1 200 OK\\r\\nDate: ...\\r\\nContent-Type: text/plain\\r\\nContent-Length: 30\\r\\nConnection: close\\r\\nServer: gunicorn/19.9.0\\r\\nAccess-Control-Allow-Origin: *\\r\\nAccess-Control-Allow-Credentials: true\\r\\n\\r\\nUser-agent: *\\nDisallow: /deny\\n'
    >>> get('mhasbini.com', 1234, '/robots.txt')
    Traceback (most recent call last):
        ...
    tt2.ConnectionError: [Errno 113] No route to host
    """

    # Generate request message 
    request_m  = f'GET {path} HTTP/1.1\r\n'
    request_m += f'Host: {host}:{port}\r\n'
    request_m += 'Connection: close\r\n'
    request_m += '\r\n'

    try:
        # AF_INET -> ipv4
        # SOCK_STREAM -> TCP
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.connect((host, port))
        sock.sendall(request_m.encode())

        # Get data 1024 bytes at a time
        data = b''
        while True:
            _buffer = sock.recv(1024)

            if not _buffer:
                break

            data += _buffer

        sock.close()

        return data.decode()
    except OSError as e:
        raise ConnectionError(str(e)) from None