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】
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[i] ^ mask[i % 4] bytes_list.append(chunk) body = str(bytes_list, encoding='utf-8') print(body)
解包详细过程：
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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('\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 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\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" 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[i] ^ 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
<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title></title> </head> <body> <div> <input type="text" id="txt"/> <input type="button" id="btn" value="提交" onclick="sendMsg();"/> <input type="button" id="close" value="关闭连接" onclick="closeConn();"/> </div> <div id="content"></div> <script type="text/javascript"> var socket = new WebSocket("ws://127.0.0.1:8003/chatsocket"); socket.onopen = function () { /* 与服务器端连接成功后，自动执行 */ var newTag = document.createElement('div'); newTag.innerHTML = "【连接成功】"; document.getElementById('content').appendChild(newTag); }; socket.onmessage = function (event) { /* 服务器端向客户端发送数据时，自动执行 */ var response = event.data; var newTag = document.createElement('div'); newTag.innerHTML = response; document.getElementById('content').appendChild(newTag); }; socket.onclose = function (event) { /* 服务器端主动断开连接时，自动执行 */ var newTag = document.createElement('div'); newTag.innerHTML = "【关闭连接】"; document.getElementById('content').appendChild(newTag); }; function sendMsg() { var txt = document.getElementById('txt'); socket.send(txt.value); txt.value = ""; } function closeConn() { socket.close(); var newTag = document.createElement('div'); newTag.innerHTML = "【关闭连接】"; document.getElementById('content').appendChild(newTag); } </script> </body> </html>
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()
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Python聊天室</title> </head> <body> <div> <input type="text" id="txt"/> <input type="button" id="btn" value="提交" onclick="sendMsg();"/> <input type="button" id="close" value="关闭连接" onclick="closeConn();"/> </div> <div id="container" style="border: 1px solid #dddddd;margin: 20px;min-height: 500px;"> </div> <script src="/static/jquery-2.1.4.min.js"></script> <script type="text/javascript"> $(function () { wsUpdater.start(); }); var wsUpdater = { socket: null, uid: null, start: function() { var url = "ws://127.0.0.1:8888/chat"; wsUpdater.socket = new WebSocket(url); wsUpdater.socket.onmessage = function(event) { console.log(event); if(wsUpdater.uid){ wsUpdater.showMessage(event.data); }else{ wsUpdater.uid = event.data; } } }, showMessage: function(content) { $('#container').append(content); } }; function sendMsg() { var msg = { uid: wsUpdater.uid, message: $("#txt").val() }; wsUpdater.socket.send(JSON.stringify(msg)); } </script> </body> </html>
