WebSocket的通信过程与实现方法详解

GET / HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Host: example.com
Origin: http://example.com
Sec-WebSocket-Key: sN9cRrP/n9NdMgdcy2VJFQ==
Sec-WebSocket-Version: 13

Upgrade: websocket
Connection: Upgrade

Sec-WebSocket-Key: sN9cRrP/n9NdMgdcy2VJFQ==
Sec-WebSocket-Version: 13

var ws = new websocket("ws://127.0.0.1:8001");

<script type="text/javascript">
 var ws;
 var box = document.getElementById('box');

 function startWS() {
 ws = new WebSocket('ws://127.0.0.1:8001');
 ws.onopen = function (msg) {
 console.log('WebSocket opened!');
 };
 ws.onmessage = function (message) {
 console.log('receive message: ' + message.data);
 box.insertAdjacentHTML('beforeend', '<p>' + message.data + '</p>');
 };
 ws.onerror = function (error) {
 console.log('Error: ' + error.name + error.number);
 };
 ws.onclose = function () {
 console.log('WebSocket closed!');
 };
 }

 function sendMessage() {
 console.log('Sending a message...');
 var text = document.getElementById('text');
 ws.send(text.value);
 }

 window.onbeforeunload = function () {
 ws.onclose = function () {}; // 首先关闭 WebSocket
 ws.close()
 };
</script>

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat

def create_socket():
 # 启动 Socket 并监听连接
 sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 try:
 sock.bind(('127.0.0.1', 8001))

 # 操作系统会在服务器 Socket 被关闭或服务器进程终止后马上释放该服务器的端口，否则操作系统会保留几分钟该端口。
 sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 sock.listen(5)
 except Exception as e:
 logging.error(e)
 return
 else:
 logging.info('Server running...')

 # 等待访问
 while True:
 conn, addr = sock.accept() # 此时会进入 waiting 状态

 data = str(conn.recv(1024))
 logging.debug(data)

 header_dict = {}
 header, _ = data.split(r'\r\n\r\n', 1)
 for line in header.split(r'\r\n')[1:]:
 key, val = line.split(': ', 1)
 header_dict[key] = val

 if 'Sec-WebSocket-Key' not in header_dict:
 logging.error('This socket is not websocket, client close.')
 conn.close()
 return

 magic_key = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
 sec_key = header_dict['Sec-WebSocket-Key'] + magic_key
 key = base64.b64encode(hashlib.sha1(bytes(sec_key, encoding='utf-8')).digest())
 key_str = str(key)[2:30]
 logging.debug(key_str)

 response = 'HTTP/1.1 101 Switching Protocols\r\n' \
  'Connection: Upgrade\r\n' \
  'Upgrade: websocket\r\n' \
  'Sec-WebSocket-Accept: {0}\r\n' \
  'WebSocket-Protocol: chat\r\n\r\n'.format(key_str)
 conn.send(bytes(response, encoding='utf-8'))
 logging.debug('Send the handshake data')
 WebSocketThread(conn).start()

def read_msg(data):
 logging.debug(data)

 msg_len = data[1] & 127 # 数据载荷的长度
 if msg_len == 126:
 mask = data[4:8] # Mask 掩码
 content = data[8:] # 消息内容
 elif msg_len == 127:
 mask = data[10:14]
 content = data[14:]
 else:
 mask = data[2:6]
 content = data[6:]

 raw_str = '' # 解码后的内容
 for i, d in enumerate(content):
 raw_str += chr(d ^ mask[i % 4])
 return raw_str

struct.pack(fmt, v1, v2, ...)

def write_msg(message):
 data = struct.pack('B', 129) # 写入第一个字节，10000001

 # 写入包长度
 msg_len = len(message)
 if msg_len <= 125:
  data += struct.pack('B', msg_len)
 elif msg_len <= (2 ** 16 - 1):
  data += struct.pack('!BH', 126, msg_len)
 elif msg_len <= (2 ** 64 - 1):
  data += struct.pack('!BQ', 127, msg_len)
 else:
  logging.error('Message is too long!')
  return

 data += bytes(message, encoding='utf-8') # 写入消息内容
 logging.debug(data)
 return data