I. Essence of Web Framework

All Web applications are essentially a socket server, and the user's browser is a socket client.

Return different contents according to different paths

You can write several simple pages and then access the corresponding page test by http://127.0.0.1:8080/page name

import socket

server = socket.socket()  # The default is TCP Agreement
server.bind(('127.0.0.1',8080))  # binding IP port
server.listen(5)  # Monitoring Semi-Link Pool: Protecting Computer Security

while True:
    conn, addr = server.accept()   # Waiting for connection
    data = conn.recv(1024)         # Receiving client information
    # follow HTTP Protocol, which adds a response status line to the response message
    conn.send(b'HTTP/1.1 200 OK\r\n\r\n')
    res = data.decode('utf-8')
    current_path = res.split('\r\n')[0].split(' ')[1]  # String Cutting, Getting Path
    # print(current_path)
    # Return different contents according to different paths
    if current_path == '/index':
        # conn.send(b'index')
        with open('templates/111.html','rb') as f:
            conn.send(f.read())
    elif current_path == '/login':
        conn.send(b'login')
    else:
        conn.send(b'404')
    conn.close()

Browser access page request information:

HTTP protocol mainly specifies the communication format between client and server

Response-related information can be seen in the network tab of the browser debug window. You can cut pages to get the required requests based on view information

First line of request
b'GET / HTTP/1.1\r\n  
Request header
Host: 127.0.0.1:8080\r\n
Connection: keep-alive\r\n
Cache-Control: max-age=0\r\n
Upgrade-Insecure-Requests: 1\r\n
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.142 Safari/537.36\r\n
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3\r\n
Accept-Encoding: gzip, deflate, br\r\n
Accept-Language: zh-CN,zh;q=0.9,en;q=0.8\r\n
Cookie: csrftoken=3vPenhmlRQb8Tvl4okwYM0OZpDCl3P7rbxvfpRDOHJy1zUApw89ugxM6OZSxhIBM\r\n
\r\n
//Requestor
'
http://127.0.0.1:8080/index
view Open:

Return different page requests according to different paths - Functional Edition

import socket

sk = socket.socket()
sk.bind(('127.0.0.1',8001))
sk.listen()

# Encapsulating different parts of content into functions
def index(url):
    # read index.html Page content
    with open("index.html",'rb',encoding="utf-8") as f:
        s = f.read()
    # Returns byte data
    return bytes(s,encoding="utf-8")

def login(url):
    with open("login.html",'rb',encoding="utf-8") as f:
        s = f.read()
    return bytes(s, encoding="utf-8")

list1= [
    ("templates/111.html","/index"),
    ("templates/login.html",'/login'),
]

while True:
    # Waiting for connection
    conn,add = sk.accept()
    data = conn.recv(1024) # Receive messages from clients
    # from data Get the path in
    data = str(data,encoding='utf-8') # Converting received byte-type data into strings
    print("data>>>",data)
    # Press\r\n cutting,url Access paths separated from messages sent from browsers
    url = data.split("\r\n")[0].split(' ')[1]
    print("url>>>>",url)
    conn.send(b'HTTP/1.1 200 OK\r\n\r\n') #follow http Protocol, so the message to reply also needs to add status line
    # Return different contents according to different paths. reponse Is the specific responder
    func = None
    for i in list1:
        if i[0].split("/")[1] == url:
            func = i[1]
            break
    # print("func>>>",func)
    if func:
        reponse = func(url)
    else:
        reponse = b"404 not found!"

    conn.send(reponse)
    conn.close()

# There are still some problems.//TODO

Server applications and Applications

For python web programs in real development, they are generally divided into two parts: server programs and applications.
The server program is responsible for encapsulating the socket server and sorting out all kinds of data requested when the request arrives.

The application is responsible for specific logical processing. In order to facilitate the development of applications, there are many Web frameworks, such as Django, Flask, web.py and so on. Different frameworks have different ways of development, but in any case, the developed applications must cooperate with server programs in order to provide services for users.

WSGI (Web Server Gateway Interface) is a specification that defines the interface format between web applications written in Python and web server programs, and realizes the decoupling between web applications and web server programs.

uwsgi and Gunicorn are commonly used WSGI servers. The independent WSGI server provided by Python standard library is called wsgiref, and the Django development environment uses this module as the server.

1.wsgiref module

Using wsgiref module to replace the socket server part of our own web Framework

# Pre-splitting code
# http://127.0.0.1/index accesses the corresponding name to the corresponding page
from wsgiref.simple_server import make_server

def index():
    return 'index'

def reg():
    return 'res'

def login():
    return 'login'

def error():
    return '404'

urls = [
    ('/index',index),
    ('/reg',reg),
    ('/login',login),
]

def run(env,reponse):
    reponse('200 OK', [])  # Fixed format
    print(env)  # Processing http format data, forming a field for you to call
    current_path = env.get('PATH_INFO')
    # if current_path == '/index':
    #     return [b'index']
    func = None
    for url_tuple in urls:
        if current_path == url_tuple[0]:
            func = url_tuple[1]   # If the routing matches, go back to the corresponding function
            break
    if func:
        res = func()
    else:
        res = error()
    return [res.encode('utf-8')]

if __name__ == '__main__':
    server = make_server('127.0.0.1',8080,run)  # Always listen for addresses, and whenever there is a request, it calls the last function or object: run() to execute
    server.serve_forever()

# urls.py Store pages with access links

from views import *
urls = [
    ('/index',index),
    ('/reg',reg),
    ('/login',login),
]


# views.py Store access page functions
def index():
    return 'index'

def reg():
    return 'res'

def login():
    return 'login'

def error():
    return '404'

# wsgiref.py Storage startup
from wsgiref.simple_server import make_server
from urls import urls
from views import *

def run(env,response):
    response('200 OK', [])  # Fixed format does not need to be mastered
    print(env)  # take http Format data is processed to form a field for you to call
    current_path = env.get('PATH_INFO')
    func = None
    for url_tuple in urls:
        if current_path == url_tuple[0]:
            func = url_tuple[1]  # If the routing matches, go back to the corresponding function.
            break
    if func:
        res = func(env)
    else:
        res = error(env)
    return [res.encode('utf-8')]

if __name__ == '__main__':
    server = make_server('127.0.0.1',8080,run)
    server.serve_forever()