import selectors

import socket

sel = selectors.DefaultSelector()

def accept(sock, mask):

    conn, addr = sock.accept()  # Should be ready  建立连接     print('accepted', conn, 'from', addr)     conn.setblocking(False)     sel.register(conn, selectors.EVENT_READ, read)#注册到时间循环列表（不立刻收，客户端可能还没有发。）如果再有活动就调用read函数

def read(conn, mask):

    data = conn.recv(1000)  # Should be ready     if data:         print('echoing', repr(data), 'to', conn)         conn.send(data)  # Hope it won't block     else:         print('closing', conn)         sel.unregister(conn)         conn.close()

sock = socket.socket()

sock.bind(('localhost', 1234)) sock.listen(100) sock.setblocking(False) sel.register(sock, selectors.EVENT_READ, accept)#先注册server对象。调用accept

while True:

    events = sel.select() #默认阻塞，有活动链接就返回活动列表     for key, mask in events:         callback = key.data         callback(key.fileobj, mask)