定义
- 什么是轮训?
- 通过定时器让程序每隔n秒执行一次操作。 什么是长轮训?
- 浏览器向后端发起请求,后端会将请求 hang 住,最多hang 30s。
如果一直不返回数据:则最多等待30s,紧接着用户立即再发送请求。
如果有数据返回:则操作数据并立即再发送请求。
PS:后台可以使用队列或redis的列表来hang主请求。轮训和长轮训目的?
由于Http请求是无状态、短连接所以服务端无法向客户端实时推送消息,
所以,我们就是可以使用:轮训和长轮训去服务端获取实时数据。
websocket是什么?
websocket是一套类似于http的协议。
扩展:
http协议:\r\n分割、请求头和请求体\r\n分割、无状态、短连接。
websocket协议:\r\n分割、创建连接后不断开、 验证+数据加密;
websocket本质:
- 就是一个创建连接后不断开的socket,当连接成功之后:
- 客户端(浏览器)会自动向服务端发送消息,包含: Sec-WebSocket-Key: iyRe1KMHi4S4QXzcoboMmw==
服务端接收之后,会对于该数据进行加密:
base64(sha1(swk + magic_string))构造响应头:
HTTP/1.1 101 Switching Protocols\r\n
Upgrade:websocket\r\n
Connection: Upgrade\r\n
Sec-WebSocket-Accept: 加密后的值\r\n
WebSocket-Location: ws://127.0.0.1:8002\r\n\r\n发给客户端(浏览器)
- 建立:双工通道,接下来就可以进行收发数据
- 发送的数据是加密,解密,根据payload_len的值进行处理:
- payload_len <=125
- payload_len ==126
- payload_len ==127
- 获取内容:
- mask_key
- 数据
根据mask_key和数据进行位运算,就可以把值解析出来。
示例
创建socket、绑定、监听、等待数据、接受数据
解析头部构造字典、base64加密、构造响应头、发送、客户端校验
客户端通过ws.seng()发送请求、服务端接受、并且send_msg加密发送
页面端
<body>
<script>
// 向127.0.0.1:8002发送一个websocket请求
ws = new WebSocket('ws://127.0.0.1:8002/')
ws.onmessage = function (event) {
console.log(event.data);
}
</script>
</body>
后台端
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
#构造socket对象
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()
#接受请求数据
data = conn.recv(8096)
#解析请求头数据
header_dict = get_headers(data)
print("---header_dict---",header_dict)
# 在验证环节对Sec-WebSocket-Key对应的值进行加密
#加密
magic_string = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
value = header_dict['Sec-WebSocket-Key'] + magic_string
ac = base64.b64encode(hashlib.sha1(value.encode('utf-8')).digest())
# 构造响应头
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://127.0.0.1:8002\r\n\r\n"
response = response_tpl %(str(ac,encoding='utf-8'),)
conn.sendall(bytes(response,encoding='utf-8'))
while True:
# 用户发过来的加密的数据
info = conn.recv(8096)
payload_len = info[1] & 127
if payload_len == 127:
extend_payload_len = info[2:10]
mask = info[10:14]
decoded = info[14:]
elif payload_len == 126:
extend_payload_len = info[2:4]
mask = info[4:8]
decoded = info[8:]
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---",body)
body = body + 'sb'
send_msg(conn,bytes(body,encoding='utf-8'))
后台输出如下:
—header_dict— {‘method’: ‘GET’, ‘url’: ‘/’, ‘protocol’: ‘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’, ‘User-Agent’: ‘Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36’, ‘Accept-Encoding’: ‘gzip, deflate, br’, ‘Accept-Language’: ‘zh-CN,zh;q=0.9’, ‘Cookie’: ‘csrftoken=Ksr2UHM7d5OLjgn6oDeqmywTY6diTZLUH0tbTlrWrVvLzvMhlB4KdnvvsFAhzFj2’, ‘Sec-WebSocket-Key’: ‘mmsKRyDDiMjZynOFubTQkg==’, ‘Sec-WebSocket-Extensions’: ‘permessage-deflate; client_max_window_bits’}
—-body— websocket
flask实现websocket
安装
pip3 install gevent-websocket
前端代码
<body>
<h1>首页</h1>
<div>
<h2>发送消息</h2>
<input id="msg" type="text" />
<input type="button" value="发送" onclick="sendMsg()">
<h2>接收消息</h2>
<div id="container">
</div>
</div>
<script src="/static/jquery-3.3.1.min.js"></script>
<script>
ws = new WebSocket('ws://127.0.0.1:5000/test');
ws.onmessage = function (event) {
var tag = document.createElement('div');
tag.className = 'msg-item';
tag.innerText = event.data;
$('#container').append(tag);
}
function sendMsg() {
ws.send($('#msg').val());
}
</script>
</body>
后端代码
from geventwebsocket.handler import WebSocketHandler
from gevent.pywsgi import WSGIServer
from flask import Flask, render_template, request
import pickle
app = Flask(__name__)
app.secret_key = 'xfsdfqw'
@app.route('/index')
def index():
return render_template('index.html')
WS_LIST = []
@app.route('/test')
def test():
ws = request.environ.get('wsgi.websocket')
if not ws:
return '请使用WebSocket协议'
# websocket连接已经成功
WS_LIST.append(ws)
while True:
# 等待用户发送消息,并接受
message = ws.receive()
# 关闭:message=None
if not message:
print("ws.close")
WS_LIST.remove(ws)
ws.close()
break
for item in WS_LIST:
item.send(message)
return "asdfasdf"
if __name__ == '__main__':
http_server = WSGIServer(('127.0.0.1', 5000,), app, handler_class=WebSocketHandler)
http_server.serve_forever()
测试效果
tornado实现
什么是Tornado?
Tornado是一个轻量级的Web框架,异步非阻塞+内置WebSocket功能。
安装:
pip3 install tornado
前端代码
<body>
<h1>首页</h1>
<div>
<h2>发送消息</h2>
<input id="msg" type="text"/> <input type="button" value="发送" onclick="sendMsg()">
<h2>接收消息</h2>
<div id="container">
</div>
</div>
<script src="/static/jquery-3.3.1.min.js"></script>
<script>
ws = new WebSocket('ws://127.0.0.1:9999/message');
ws.onmessage = function (event) {
var tag = document.createElement('div');
tag.className = 'msg-item';
tag.innerText = event.data;
$('#container').append(tag);
}
// ws.onclose = function (event) {
// // 服务端主动断开了连接
// }
function sendMsg() {
ws.send($('#msg').val());
}
// 客户端要断开连接
// ws.close()
</script>
</body>
后端代码
import tornado
from tornado.web import Application
from tornado.web import RequestHandler
from tornado.websocket import WebSocketHandler
class IndexHandler(RequestHandler):
def get(self, *args, **kwargs):
# self.write('Hello World')
self.render('index.html')
def post(self, *args, **kwargs):
user = self.get_argument('user')
self.write('成功')
WS_LIST = []
class MessageHandler(WebSocketHandler):
def check_origin(self, origin):
return True
def open(self, *args, **kwargs):
WS_LIST.append(self)
def on_message(self, message):
# self.close() 服务端主动断开连接,客户端的onclose方法自动执行
for ws in WS_LIST:
ws.write_message(message)
def on_close(self):
# 如果客户端断开连接,那么该函数就自动执行。
WS_LIST.remove(self)
settings = {
'template_path': 'templates',
'static_path': 'static',
}
app = Application([
(r"/index", IndexHandler),
(r"/message", MessageHandler),
], **settings)
if __name__ == '__main__':
app.listen(address='127.0.0.1', port=9999)
tornado.ioloop.IOLoop.instance().start()