WebSocket

发布时间：2023-09-06 01:43责任编辑：白小东关键词：Web

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：

+ View Code?

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：

+ View Code?

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)

基于Python实现解包过程（未实现长内容）

解包详细过程：

+ View Code?

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| | |

+-+-+<

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