python之websocket

python之websocket

一、websocket

   WebSocket协议是基于TCP的一种新的协议。WebSocket最初在HTML5规范中被引用为TCP连接,作为基于TCP的套接字API的占位符。它实现了浏览器与服务器全双工(full-duplex)通信。其本质是保持TCP连接,在浏览器和服务端通过Socket进行通信。

 本文将使用Python编写Socket服务端,一步一步分析请求过程!!!

1. 启动服务端

import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind(('127.0.0.1', 8002))
sock.listen(5)
# 等待用户连接
conn, address = sock.accept()
...
...
...

启动Socket服务器后,等待用户【连接】,然后进行收发数据。

2. 客户端连接

<script type="text/javascript">

    var socket = new WebSocket("ws://127.0.0.1:8002/xxoo");
    ...
</script>

当客户端向服务端发送连接请求时,不仅连接还会发送【握手】信息,并等待服务端响应,至此连接才创建成功!

3. 建立连接【握手】

import socket
 
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind(('127.0.0.1', 8002))
sock.listen(5)
# 获取客户端socket对象
conn, address = sock.accept()
# 获取客户端的【握手】信息
data = conn.recv(1024)
...
...
...
conn.send('响应【握手】信息')

请求和响应的【握手】信息需要遵循规则:

  • 从请求【握手】信息中提取 Sec-WebSocket-Key
  • 利用magic_string 和 Sec-WebSocket-Key 进行hmac1加密,再进行base64加密
  • 将加密结果响应给客户端

注:magic string为:258EAFA5-E914-47DA-95CA-C5AB0DC85B11

请求【握手】信息为:

GET /chatsocket HTTP/1.1
Host: 127.0.0.1:8002
Connection: Upgrade
Pragma: no-cache
Cache-Control: no-cache
Upgrade: websocket
Origin: http://localhost:63342
Sec-WebSocket-Version: 13
Sec-WebSocket-Key: mnwFxiOlctXFN/DeMt1Amg==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
...
...

提取Sec-WebSocket-Key值并加密:

import socket
import base64
import hashlib
 
def get_headers(data):
    """
    将请求头格式化成字典
    :param data:
    :return:
    """
    header_dict = {}
    data = str(data, encoding='utf-8')
 
    for i in data.split('\r\n'):
        print(i)
    header, body = data.split('\r\n\r\n', 1)
    header_list = header.split('\r\n')
    for i in range(0, len(header_list)):
        if i == 0:
            if len(header_list[i].split(' ')) == 3:
                header_dict['method'], header_dict['url'], header_dict['protocol'] = header_list[i].split(' ')
        else:
            k, v = header_list[i].split(':', 1)
            header_dict[k] = v.strip()
    return header_dict
 
 
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind(('127.0.0.1', 8002))
sock.listen(5)
 
conn, address = sock.accept()
data = conn.recv(1024)
headers = get_headers(data) # 提取请求头信息
# 对请求头中的sec-websocket-key进行加密
response_tpl = "HTTP/1.1 101 Switching Protocols\r\n" \
      "Upgrade:websocket\r\n" \
      "Connection: Upgrade\r\n" \
      "Sec-WebSocket-Accept: %s\r\n" \
      "WebSocket-Location: ws://%s%s\r\n\r\n"
magic_string = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
value = headers['Sec-WebSocket-Key'] + magic_string
ac = base64.b64encode(hashlib.sha1(value.encode('utf-8')).digest())
response_str = response_tpl % (ac.decode('utf-8'), headers['Host'], headers['url'])
# 响应【握手】信息
conn.send(bytes(response_str, encoding='utf-8'))
...
...
...

4.客户端和服务端收发数据

客户端和服务端传输数据时,需要对数据进行【封包】和【解包】。客户端的JavaScript类库已经封装【封包】和【解包】过程,但Socket服务端需要手动实现。

第一步:获取客户端发送的数据【解包】

基于Python实现解包过程(未实现长内容)

解包详细过程:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0                   1                   2                   3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-------+-+-------------+-------------------------------+ |F|R|R|R| opcode|M| Payload len |    Extended payload length    | |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           | |N|V|V|V|       |S|             |   (if payload len==126/127)   | | |1|2|3|       |K|             |                               | +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - + |     Extended payload length continued, if payload len == 127  | + - - - - - - - - - - - - - - - +-------------------------------+ |                               |Masking-key, if MASK set to 1  | +-------------------------------+-------------------------------+ | Masking-key (continued)       |          Payload Data         | +-------------------------------- - - - - - - - - - - - - - - - + :                     Payload Data continued ...                : + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + |                     Payload Data continued ...                | +---------------------------------------------------------------+

第二步:向客户端发送数据【封包】

def send_msg(conn, msg_bytes):
    """
    WebSocket服务端向客户端发送消息
    :param conn: 客户端连接到服务器端的socket对象,即: conn,address = socket.accept()
    :param msg_bytes: 向客户端发送的字节
    :return: 
    """
    import struct

    token = b"\x81"
    length = len(msg_bytes)
    if length < 126:
        token += struct.pack("B", length)
    elif length <= 0xFFFF:
        token += struct.pack("!BH", 126, length)
    else:
        token += struct.pack("!BQ", 127, length)

    msg = token + msg_bytes
    conn.send(msg)
    return True

也可以看看GoEasy文库的其他资料。

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