Back-end web framework with sockets

Question

I recently became interested in back end web frameworks in python, but I didn't want to use django or flask. (I want to make something similar to django or flask) So I decided to make my own. This is what I have so far. I have been programming for nearly two years and I mostly do c++. But I would like to improve my python. What can I do to improve this, or my python in general? Thanks!

import socket as Socket

class Server:
    def __init__(self, host, port):
        self.host = host
        self.port = port
        self.__run_allowed = True
        self.__HTTP_response_codes = {200: " OK", 404: " Not Found"}
        self.__socket = Socket.socket(Socket.AF_INET, Socket.SOCK_STREAM)

    def run(self):
        self.__socket.bind((self.host, self.port))
        self.__socket.listen(1)
        while self.__run_allowed:
            connection, address = self.__socket.accept()
            request = connection.recv(1024).decode("utf-8")
            webpage = request.split(' ')[1].split('?')[0].lstrip('/')
            docInfo = self.__getDocumentInfoTuple__(webpage)
            header = self.__generateHTTPResponseHeader__(docInfo[1], docInfo[2])
            connection.send(header + docInfo[0])
            connection.close()

    def __getDocumentInfoTuple__(self, page):
        print(page)
        html = None
        return_code = 200
        content_type = "text/html"
        try:
            with open(page) as file:
                html = str.encode(file.read())
        except:
            with open("404.html") as file:
                html = str.encode(file.read())
                return_code = 404
            print("Failed to find requested page!\nDefaulting to PageNotFound.html...")
        if page.endswith(".html"):
            content_type = "text/html"
        elif page.endswith(".css"):
            content_type = "text/css"
        elif page.endswith(".js"):
            content_type = "text/javascript"
        return (html, return_code, content_type)

    def __generateHTTPResponseHeader__(self, HTTP_response_code, content_type):
        header = b"HTTP/1.1 " + str.encode(str(HTTP_response_code)) + str.encode(self.__HTTP_response_codes[HTTP_response_code]) + b"\r\n"
        header += b"Content-Type: " + str.encode(content_type) + b"; Encoding: UTF-8\n\n"
        return header

def main(`enter code here`):
    server = Server("127.0.0.1", 8080)
    server.run()

if __name__ == "__main__":
    main()