标签：res nts 一个 bind recv www 监视 通知 written
I/O多路复用（multiplexing）的本质是通过一种机制（系统内核缓冲I/O数据），让单个进程可以监视多个文件描述符，一旦某个描述符就绪（一般是读就绪或写就绪），能够通知程序进行相应的读写操作。
select、poll 和 epoll 都提供的 IO 复用方式。
（1）select，poll实现需要自己不断轮询所有fd集合，直到设备就绪，期间可能要睡眠和唤醒多次交替。而epoll其实也需要调用 epoll_wait不断轮询就绪链表，期间也可能多次睡眠和唤醒交替，但是它是设备就绪时，调用回调函数，把就绪fd放入就绪链表中，并唤醒在 epoll_wait中进入睡眠的进程。虽然都要睡眠和交替，但是select和poll在“醒着”的时候要遍历整个fd集合，而epoll在“醒着”的 时候只要判断一下就绪链表是否为空就行了，这节省了大量的CPU时间，这就是回调机制带来的性能提升。
（2）select，poll每次调用都要把fd集合从用户态往内核态拷贝一次，并且要把current往设备等待队列中挂一次，而epoll只要 一次拷贝，而且把current往等待队列上挂也只挂一次（在epoll_wait的开始，注意这里的等待队列并不是设备等待队列，只是一个epoll内 部定义的等待队列），这也能节省不少的开销。
selectors实现IO多路复用
#服务端 #!/usr/bin/env python # -*- coding: utf-8 -*- import select, socket response = b"hello world" #创建一个server socket serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) serversocket.bind((‘localhost‘, 8080)) serversocket.listen(1) serversocket.setblocking(0) inputs = [serversocket, ] while True: rlist, wlist, xlist = select.select(inputs, [], []) for sock in rlist: ＃ server socket读就绪 if sock == serversocket: con, addr = serversocket.accept() ＃将这个connection添加到读就绪中 inputs.append(con) else: data = sock.recv(1024) if data: sock.send(response) ＃从读就绪的list中删除 inputs.remove(sock) sock.close() #客户端 from socket import * c=socket(AF_INET,SOCK_STREAM) c.connect((‘127.0.0.1‘,8080)) while True: msg=input(‘>>: ‘) if not msg:continue c.send(msg.encode(‘utf-8‘)) data=c.recv(1024) print(data.decode(‘utf-8‘))
poll实现IO多路复用
server端：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import select, socket
response = b"hello world"
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
serversocket.bind((‘192.168.199.197‘, 8080))
serversocket.listen(1)
serversocket.setblocking(0)
#
poll = select.poll()
poll.register(serversocket.fileno(), select.POLLIN)
connections = {}
while True:
for fd, event in poll.poll():
if event == select.POLLIN:
if fd == serversocket.fileno():
con, addr = serversocket.accept()
poll.register(con.fileno(), select.POLLIN)
connections[con.fileno()] = con
else:
con = connections[fd]
data = con.recv(1024)
if data:
poll.modify(con.fileno(), select.POLLOUT)
elif event == select.POLLOUT:
con = connections[fd]
con.send(response)
poll.unregister(con.fileno())
con.close()
epoll实现IO多路复用
import socket, select EOL1 = b‘\n\n‘ EOL2 = b‘\n\r\n‘ response = b‘HTTP/1.0 200 OK\r\nDate: Mon, 1 Jan 1996 01:01:01 GMT\r\n‘ response += b‘Content-Type: text/plain\r\nContent-Length: 13\r\n\r\n‘ response += b‘Hello, world!‘ serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) serversocket.bind((‘0.0.0.0‘, 8080)) serversocket.listen(1) serversocket.setblocking(0) epoll = select.epoll() epoll.register(serversocket.fileno(), select.EPOLLIN) try: connections = {}; requests = {}; responses = {} while True: events = epoll.poll(1) for fileno, event in events: if fileno == serversocket.fileno(): connection, address = serversocket.accept() connection.setblocking(0) epoll.register(connection.fileno(), select.EPOLLIN) connections[connection.fileno()] = connection requests[connection.fileno()] = b‘‘ responses[connection.fileno()] = response elif event & select.EPOLLIN: requests[fileno] += connections[fileno].recv(1024) if EOL1 in requests[fileno] or EOL2 in requests[fileno]: epoll.modify(fileno, select.EPOLLOUT) print(‘-‘*40 + ‘\n‘ + requests[fileno].decode()[:-2]) elif event & select.EPOLLOUT: byteswritten = connections[fileno].send(responses[fileno]) responses[fileno] = responses[fileno][byteswritten:] if len(responses[fileno]) == 0: epoll.modify(fileno, 0) connections[fileno].shutdown(socket.SHUT_RDWR) elif event & select.EPOLLHUP: epoll.unregister(fileno) connections[fileno].close() del connections[fileno] finally: epoll.unregister(serversocket.fileno()) epoll.close() serversocket.close()
详情见：https://www.cnblogs.com/9527chu/p/5661932.html
标签：res nts 一个 bind recv www 监视 通知 written
原文地址：https://www.cnblogs.com/lvxw/p/11028454.html
