了解了http协议之后，我们就可以制作一个简单的WEB应用程序了。
在之前学习的网络编程的前提下，我们知道，浏览器就相当于一个socket客户端，服务器相当于一个socket服务端。
客户端既然就是浏览器那么就不需要我们再来实现了，我们只需要编写服务端就可以了。
import socket
if __name__ == '__main__':
# 实例化socket对象
server = socket.socket()
# 绑定服务端IP和端口
server.bind(("127.0.0.1", 7777))
# 设置最大监听数
server.listen(7)
while True:
print('Server waiting...')
# 与客户端请求建立链接
connect, address = server.accept()
# 接收客户端数据
data = connect.recv(1024)
print('data = %s' % data)
# 读取要返回的HTML文档，注意，一定要以rb的模式读，因为要返回bytes类型的数据
with open('Hello_Http.html', 'rb') as f:
html = f.read()
# 响应数据要设置响应首行，否则浏览器无法解析，响应头可以省略，响应首行与响应体之间以\r\n\r\n分隔
connect.send(b'HTTP/1.1 200OK\r\n\r\n%s' % html)
connect.close()
相应的HTML文档为：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Hello Http</title>
</head>
<body>
<img src="https://www.baidu.com/img/bd_logo1.png" alt='百度一下'>
<form action="http://127.0.0.1:7777/" method="post">
<span>用户名：</span>
<label>
<input type="text" name="username">
</label>
<span>密码：</span>
<label>
<input type="password" name="password">
</label>
<label>
<input type="submit">
</label>
</form>
</body>
</html>
浏览器显示效果为：
使用form表单提交数据之后终端的输出：
Server waiting...
data = b'GET / HTTP/1.1\r\nHost: 127.0.0.1:7777\r\nConnection: keep-alive\r\nCache-Control: max-age=0\r\nUpgrade-Insecure-Requests: 1\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36\r\nSec-Fetch-Dest: document\r\nAccept: 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\r\nSec-Fetch-Site: none\r\nSec-Fetch-Mode: navigate\r\nSec-Fetch-User: ?1\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7\r\n\r\n'
Server waiting...
data = b'GET /favicon.ico HTTP/1.1\r\nHost: 127.0.0.1:7777\r\nConnection: keep-alive\r\nPragma: no-cache\r\nCache-Control: no-cache\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36\r\nSec-Fetch-Dest: image\r\nAccept: image/webp,image/apng,image/*,*/*;q=0.8\r\nSec-Fetch-Site: same-origin\r\nSec-Fetch-Mode: no-cors\r\nReferer: http://127.0.0.1:7777/\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7\r\n\r\n'
Server waiting...
data = b'POST / HTTP/1.1\r\nHost: 127.0.0.1:7777\r\nConnection: keep-alive\r\nContent-Length: 30\r\nCache-Control: max-age=0\r\nOrigin: http://127.0.0.1:7777\r\nUpgrade-Insecure-Requests: 1\r\nContent-Type: application/x-www-form-urlencoded\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36\r\nSec-Fetch-Dest: document\r\nAccept: 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\r\nSec-Fetch-Site: same-origin\r\nSec-Fetch-Mode: navigate\r\nSec-Fetch-User: ?1\r\nReferer: http://127.0.0.1:7777/\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7\r\n\r\nusername=Alex&password=1234567'
Server waiting...
data = b'GET /favicon.ico HTTP/1.1\r\nHost: 127.0.0.1:7777\r\nConnection: keep-alive\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36\r\nSec-Fetch-Dest: image\r\nAccept: image/webp,image/apng,image/*,*/*;q=0.8\r\nSec-Fetch-Site: same-origin\r\nSec-Fetch-Mode: no-cors\r\nReferer: http://127.0.0.1:7777/\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7\r\n\r\n'
Server waiting...
第一次和第二次get请求为通过浏览器请求页面，包含以下内容：
请求首行：
GET / HTTP/1.1
\r\n
请求头：
Host: 127.0.0.1:7777\r\nConnection: keep-alive\r\nCache-Control: max-age=0\r\nUpgrade-Insecure-Requests: 1\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36\r\nSec-Fetch-Dest: document\r\nAccept: 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\r\nSec-Fetch-Site: none\r\nSec-Fetch-Mode: navigate\r\nSec-Fetch-User: ?1\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7
\r\n\r\n
请求体：
无
请求首行与请求头以\r\n为分隔，请求头中的数据也都已\r\n为分隔，请求头与请求体以\r\n\r\n为分隔。
第三个post请求为浏览器通过form表单发送给服务端的请求，包含以下内容：
请求首行：
POST / HTTP/1.1
\r\n
请求头：
Host: 127.0.0.1:7777\r\nConnection: keep-alive\r\nContent-Length: 30\r\nCache-Control: max-age=0\r\nOrigin: http://127.0.0.1:7777\r\nUpgrade-Insecure-Requests: 1\r\nContent-Type: application/x-www-form-urlencoded\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36\r\nSec-Fetch-Dest: document\r\nAccept: 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\r\nSec-Fetch-Site: same-origin\r\nSec-Fetch-Mode: navigate\r\nSec-Fetch-User: ?1\r\nReferer: http://127.0.0.1:7777/\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7
\r\n\r\n
请求体：
username=Alex&password=1234567
我们的服务端应用程序设置为不管发起何种请求，返回的响应数据都是唯一的：
HTTP/1.1 200OK\r\n\r\n%s
响应首行：
HTTP/1.1 200OK
响应头：
无
\r\n\r\n
响应体：
(HTML文档)
