# websocket实现原理

'''

1.服务端开启socket，监听ip和端口

2.客户端发送连接请求（带上ip和端口）

3.服务端允许连接

4.客户端生成一个随机字符串，和magic string组合进行一个sha1加密，加密。并将随机字符串发送给服务端

5.然后服务端也要用相同的方式进行加密。

6.然后服务端将加密之后的密串返回给客户端

7.客户端将服务端返回的密串和自己加密之后的密串进行比对，如果一样，说明遵循同样的协议。如果不一样，就没法玩了·····

'''

import socket

import base64

import hashlib

from pprint import pprint

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

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

server.bind(('localhost', 8080))

server.listen(5)

# 等待用户连接

conn, addr = server.accept()

# 握手消息

content = conn.recv(1024)

'''

>>> print(content)

b'GET / HTTP/1.1\r\nHost: localhost:8080\r\nConnection: Upgrade\r\nPragma: no-cache\r\nCache-Control: no-cache\r\nUpgrade: websocket\r\nOrigin: http://localhost:63342\r\nSec-WebSocket-Version: 13\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: zh-CN,zh;q=0.9\r\nCookie: uuid=81a68694c772e0c62d4a5a3c256fe3e0; sensorsdata2015jssdkcross=%7B%22distinct_id%22%3A%2216453a8bf2bbe-09a40e8e58a866-5e442e19-1fa400-16453a8bf2c745%22%7D; Hm_lvt_2af69bc2b378fb58ae04ed2a04257ed1=1530411925; Pycharm-bdfc5fce=a920e49d-da4e-4d2f-a76e-17acfacc6462\r\nSec-WebSocket-Key: 1y6WpsSgfF80wqi3HpmrqQ==\r\nSec-WebSocket-Extensions: permessage-deflate; client_max_window_bits\r\n\r\n'

'''

# 获取请求头

headers = get_headers(content)

'''

>>>pprint(headers)

{'Cache-Control': 'no-cache',

 'Connection': 'Upgrade',

 'Cookie': 'Pycharm-bdfc5fce=a920e49d-da4e-4d2f-a76e-17acfacc6462',

 'Host': 'localhost:8080',

 'Origin': 'http://localhost:63342',

 'Sec-WebSocket-Key': 'RRGDeYeYSGEP9eHy85u8oQ==',

 'Sec-WebSocket-Version': '13',

 'Upgrade': 'websocket',

 'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) '

               'like Gecko',

 'method': 'GET',

 'protocol': 'HTTP/1.1',

 'url': '/'}

'''

# 规定：魔法字符串就叫这个

magic_string = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"

# 获取随机密串，并将其与魔法字符串组合

value = headers["Sec-WebSocket-Key"] + magic_string

# 进行加密,规定，只能按照此加密方式

hash_str = base64.b64encode(hashlib.sha1(bytes(value, encoding='utf-8')).digest())

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"

# 获取握手消息，组合魔法字符串，进行sha1加密

# 发送给客户端

response_str = response_tpl % (str(hash_str, encoding='utf-8'), headers['Host'], headers['url'])

conn.send(bytes(response_str, encoding='utf-8'))

# 也可以发送数据

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

# 那么便可以接受数据了，注意接受的数据必须按照一定的规则才能够获取

while True:

    info = conn.recv(1024)

    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)

    # 可以将获取的body加上新的字符

    body = body + "我是你爸"

    send_msg(conn, bytes(body, encoding="utf-8"))