08-27-周三_17-09-29
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Python/Flask框架/web框架的本质.md
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Python/Flask框架/web框架的本质.md
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# 自定义web框架
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web应用本质上就是一个socket服务端，浏览器是socket客户端，基于请求做出响应，客户都先请求，服务端做出对应的响应，按照http协议的请求协议发送请求，服务端按照http协议的响应协议来响应请求，这样的网络通信，我们就可以自己实现Web框架了。
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准备一个html文件
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```html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>测试页面</title>
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</head>
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<body>
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<h1>标题1</h1>
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<img src="https://iproute.cn/images/logo.png" alt="头像">
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</body>
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</html>
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```
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编写python的socket服务端
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```python
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import socket
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sk = socket.socket()
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sk.bind(('127.0.0.1',8080))
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sk.listen()
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conn,addr = sk.accept()
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b_msg = conn.recv(1024)
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str_msg = b_msg.decode('utf-8')
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conn.send(b'HTTP/1.1 200 ok \r\n\r\n')
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conn.send(b'hello')
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print(str_msg)
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conn.close()
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sk.close()
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```
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运行服务端之后，浏览器访问`http://127.0.0.1:8080` ，浏览器传给socket的内容如下
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```
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GET / HTTP/1.1 # 请求行，其中的/是路径
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Host: 127.0.0.1:8080
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Connection: keep-alive
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Upgrade-Insecure-Requests: 1
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User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.116 Safari/537.36
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Sec-Fetch-Dest: document
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Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
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Sec-Fetch-Site: none
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Sec-Fetch-Mode: navigate
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Sec-Fetch-User: ?1
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Accept-Encoding: gzip, deflate, br
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Accept-Language: zh-CN,zh;q=0.9,zh-TW;q=0.8
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Cookie: smid=sys4OxpO9GZqFqSAA37ZAWOnLB54KsilDWWuipaewHYE9ggajIeWtlHRrIBuSZyR038Q7r4c2XNUXdfdWR-I4A; APP_HOST=http%3A//127.0.0.1%3A49153/; HOST=http%3A//127.0.0.1%3A49153/; kodUserLanguage=zh-CN; kodUserID=1; X-CSRF-TOKEN=i9YQRqWXnS4Iy3uRt3vW; p_h5_u=057F0CAB-3644-4539-A2BC-249B82EA9934
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```
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修改socket服务端，让其返回网页内容
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```python
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import socket
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sk = socket.socket()
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sk.bind(('127.0.0.1',8080))
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sk.listen()
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conn,addr = sk.accept()
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b_msg = conn.recv(1024)
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str_msg = b_msg.decode('utf-8')
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print(str_msg)
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conn.send(b'HTTP/1.1 200 ok \r\n\r\n')
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with open('test.html','rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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sk.close()
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```
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这样就可以将网页内容返回给浏览器了
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如果想要在网页中携带本地路径的图片，那么修改html代码
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```html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>测试页面</title>
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</head>
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<body>
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<h1>标题1</h1>
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<img src="logo.png" alt="头像">
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</body>
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</html>
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```
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然后修改socket服务端
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```python
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import socket
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sk = socket.socket()
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sk.bind(('127.0.0.1',8080))
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sk.listen()
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while 1: # 浏览器多次访问，所以需要while
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conn,addr = sk.accept()
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b_msg = conn.recv(1024)
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str_msg = b_msg.decode('utf-8')
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path = str_msg.split('\r\n')[0].split(' ')[1]
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print('path>>>',path)
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conn.send(b'HTTP/1.1 200 ok \r\n\r\n')
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if path == '/':
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with open('test.html','rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close() # HTTP协议是短链接的，一次请求对应一次响应，这个请求就结束了，所以我们需要写上close，不然浏览器自己断了
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elif path == '/logo.png':
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with open('logo.png','rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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sk.close()
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```
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可以改成使用函数的版本
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```python
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import socket
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sk = socket.socket()
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sk.bind(('127.0.0.1',8080))
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sk.listen()
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def func1(conn):
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with open('test.html', 'rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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def func2(conn):
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with open('logo.png', 'rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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while 1:
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conn,addr = sk.accept()
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b_msg = conn.recv(1024)
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str_msg = b_msg.decode('utf-8')
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path = str_msg.split('\r\n')[0].split(' ')[1]
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print('path>>>',path)
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conn.send(b'HTTP/1.1 200 ok \r\n\r\n')
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if path == '/':
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func1(conn)
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elif path == '/logo.png':
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func2(conn)
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sk.close()
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```
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现在还不支持高并发的情况，可以加上多线程
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```python
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import socket
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from threading import Thread
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sk = socket.socket()
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sk.bind(('127.0.0.1',8080))
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sk.listen()
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def func1(conn):
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with open('test.html', 'rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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def func2(conn):
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with open('logo.png', 'rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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while 1:
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conn,addr = sk.accept()
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b_msg = conn.recv(1024)
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str_msg = b_msg.decode('utf-8')
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path = str_msg.split('\r\n')[0].split(' ')[1]
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print('path>>>',path)
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conn.send(b'HTTP/1.1 200 ok \r\n\r\n')
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if path == '/':
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t = Thread(target=func1,args=(conn,))
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t.start()
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elif path == '/logo.png':
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t = Thread(target=func2,args=(conn,))
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t.start()
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sk.close()
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```
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替换字符串，实现不同的时间访问返回时间戳模拟动态内容
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在网页中，用特殊的符号`@@666@@`表示需要被替换掉的地方，修改html代码
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```html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>测试页面</title>
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</head>
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<body>
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<h1>标题1</h1>
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<img src="logo.png" alt="头像">
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<h2>@@666@@</h2>
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</body>
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</html>
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```
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修改socket服务端
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```python
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import socket
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from threading import Thread
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import time
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sk = socket.socket()
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sk.bind(('127.0.0.1',8080))
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sk.listen()
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def func1(conn):
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with open('test.html', 'r',encoding="utf-8") as f:
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f_data = f.read()
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now = str(time.time())
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f_data = f_data.replace("@@666@@",now).encode('utf-8')
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conn.send(f_data)
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conn.close()
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def func2(conn):
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with open('logo.png', 'rb') as f:
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f_data = f.read()
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conn.send(f_data)
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conn.close()
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while 1:
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conn,addr = sk.accept()
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b_msg = conn.recv(1024)
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str_msg = b_msg.decode('utf-8')
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path = str_msg.split('\r\n')[0].split(' ')[1]
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print('path>>>',path)
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conn.send(b'HTTP/1.1 200 ok \r\n\r\n')
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if path == '/':
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t = Thread(target=func1,args=(conn,))
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t.start()
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elif path == '/logo.png':
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t = Thread(target=func2,args=(conn,))
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t.start()
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sk.close()
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```
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