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 socketsock = 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

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/1.1Host: 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 socketimport 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(´
´):
        print(i)
    header, body = data.split(´
´, 1)
    header_list = header.split(´
´)
    for i in range(0, len(header_list)):
        if i == 0:
            if len(header_list.split(´ ´)) == 3:
                header_dict[´method´], header_dict[´url´], header_dict[´protocol´] = header_list.split(´ ´)
        else:
            k, v = header_list.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
" 
      "Upgrade:websocket
" 
      "Connection: Upgrade
" 
      "Sec-WebSocket-Accept: %s
" 
      "WebSocket-Location: ws://%s%s
"
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】

info = conn.recv(8096)
payload_len = info[1] & 127
if payload_len == 126:
extend_payload_len = info[2:4]
mask = info[4:8]
decoded = info[8:]
elif payload_len == 127:
extend_payload_len = info[2:10]
mask = info[10:14]
decoded = info[14:]
else:
extend_payload_len = None
mask = info[2:6]
decoded = info[6:]
bytes_list = bytearray()
for i in range(len(decoded)):
chunk = decoded ^ mask[i % 4]
bytes_list.append(chunk)
body = str(bytes_list, encoding=´utf-8´)
print(body)

解包详细过程：

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

5. 基于Python实现简单示例a. 基于Python socket实现的WebSocket服务端：

#!/usr/bin/env python# -*- coding:utf-8 -*-
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´)
 
    header, body = data.split(´
´, 1)
    header_list = header.split(´
´)
    for i in range(0, len(header_list)):
        if i == 0:
            if len(header_list.split(´ ´)) == 3:
                header_dict[´method´], header_dict[´url´], header_dict[´protocol´] = header_list.split(´ ´)
        else:
            k, v = header_list.split(´:´, 1)
            header_dict[k] = v.strip()
    return header_dict
 
 
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
 
 
def run():
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind((´127.0.0.1´, 8003))
    sock.listen(5)
 
    conn, address = sock.accept()
    data = conn.recv(1024)
    headers = get_headers(data)
    response_tpl = "HTTP/1.1 101 Switching Protocols
" 
                   "Upgrade:websocket
" 
                   "Connection:Upgrade
" 
                   "Sec-WebSocket-Accept:%s
" 
                   "WebSocket-Location:ws://%s%s
"
 
    value = headers[´Sec-WebSocket-Key´] + ´258EAFA5-E914-47DA-95CA-C5AB0DC85B11´
    ac = base64.b64encode(hashlib.sha1(value.encode(´utf-8´)).digest())
    response_str = response_tpl % (ac.decode(´utf-8´), headers[´Host´], headers[´url´])
    conn.send(bytes(response_str, encoding=´utf-8´))
 
    while True:
        try:
            info = conn.recv(8096)
        except Exception as e:
            info = None
        if not info:
            break
        payload_len = info[1] & 127
        if payload_len == 126:
            extend_payload_len = info[2:4]
            mask = info[4:8]
            decoded = info[8:]
        elif payload_len == 127:
            extend_payload_len = info[2:10]
            mask = info[10:14]
            decoded = info[14:]
        else:
            extend_payload_len = None
            mask = info[2:6]
            decoded = info[6:]
 
        bytes_list = bytearray()
        for i in range(len(decoded)):
            chunk = decoded ^ mask[i % 4]
            bytes_list.append(chunk)
        body = str(bytes_list, encoding=´utf-8´)
        send_msg(conn,body.encode(´utf-8´))
 
    sock.close()
 
if __name__ == ´__main__´:
    run()

b. 利用JavaScript类库实现客户端

6. 基于Tornado框架实现Web聊天室

Tornado是一个支持WebSocket的优秀框架，其内部原理正如1~5步骤描述，当然Tornado内部封装功能更加完整。

以下是基于Tornado实现的聊天室示例：

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import uuid
import json
import tornado.ioloop
import tornado.web
import tornado.websocket
class IndexHandler(tornado.web.RequestHandler):
def get(self):
self.render(´index.html´)
class ChatHandler(tornado.websocket.WebSocketHandler):
# 用户存储当前聊天室用户
waiters = set()
# 用于存储历时消息
messages = []
def open(self):
"""
客户端连接成功时，自动执行
:return:
"""
ChatHandler.waiters.add(self)
uid = str(uuid.uuid4())
self.write_message(uid)
for msg in ChatHandler.messages:
content = self.render_string(´message.html´, **msg)
self.write_message(content)
def on_message(self, message):
"""
客户端连发送消息时，自动执行
:param message:
:return:
"""
msg = json.loads(message)
ChatHandler.messages.append(message)
for client in ChatHandler.waiters:
content = client.render_string(´message.html´, **msg)
client.write_message(content)
def on_close(self):
"""
客户端关闭连接时，，自动执行
:return:
"""
ChatHandler.waiters.remove(self)
def run():
settings = {
´template_path´: ´templates´,
´static_path´: ´static´,
}
application = tornado.web.Application([
(r"/", IndexHandler),
(r"/chat", ChatHandler),
], **settings)
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
if __name__ == "__main__":
run()

π导航

python之websocket

1. 启动服务端

2. 客户端连接

3. 建立连接【握手】

4.客户端和服务端收发数据

5. 基于Python实现简单示例

6. 基于Tornado框架实现Web聊天室