python的epoll及EPOLLLT

Posted 2020-08-14

今天没事练习python的epoll，一开始写了个客户端：

#! /usr/python

import socket,sys,select

c=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
host = ‘127.0.0.1‘
port=57777
c.connect((host,port))

epoll_fd = select.epoll()

epoll_fd.register(c.fileno(),select.EPOLLIN)
epoll_fd.register(sys.stdin.fileno(), select.EPOLLIN)
str=""
while True:
    e_list = epoll_fd.poll()
    for fd,events in e_list:
      if fd == c.fileno() and events&select.EPOLLIN:
        buf =  c.recv(1024)
        if not len(buf):
           break
        print "ser:",buf
      if fd == c.fileno() and events & select.EPOLLOUT:
        #print ‘send msg to ser.‘
        c.send(str)
        epoll_fd.modify(c.fileno(), select.EPOLLIN)
      if fd == sys.stdin.fileno() and events & select.EPOLLIN:
        str="ssf"
        epoll_fd.modify(c.fileno(), select.EPOLLOUT)

c.close()

发现服务端总是进入死循环收信息，甚是迷惑。后来修改了 str="ssf"处，修改为raw_input，发现程序正常运行，恍然醒悟，epoll默认

是LT模式，缓冲里的数据没读走，是每次都会触发的，因此，上面的代码修改epoll_fd.register(sys.stdin.fileno(), select.EPOLLIN)

为epoll_fd.register(sys.stdin.fileno(), select.EPOLLIN|select.EPOLLOUT) 也是能正常工作的。

附上最终代码：

client.py

 

#! /usr/python

import socket,sys,select

c=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
host = ‘127.0.0.1‘
port=57777
c.connect((host,port))

epoll_fd = select.epoll()

epoll_fd.register(c.fileno(),select.EPOLLIN)
epoll_fd.register(sys.stdin.fileno(), select.EPOLLIN)
str=""
while True:
    e_list = epoll_fd.poll()
    for fd,events in e_list:
      if fd == c.fileno() and events&select.EPOLLIN:
        buf =  c.recv(1024)
        if not len(buf):
           break
        print "ser:",buf
      if fd == c.fileno() and events & select.EPOLLOUT:
        #print ‘send msg to ser.‘
        c.send(str)
        epoll_fd.modify(c.fileno(), select.EPOLLIN)
      if fd == sys.stdin.fileno() and events & select.EPOLLIN:
        str=raw_input("me: ")
        epoll_fd.modify(c.fileno(), select.EPOLLOUT)

c.close()

 

简单的server和client相似

import socket, os,select,sys

host=‘127.0.0.1‘
port=57777

s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((host,port))
s.listen(10)

epoll_obj=select.epoll()

epoll_obj.register(sys.stdin.fileno(), select.EPOLLIN)

print ‘wait for connect‘

cs,caddr=s.accept()
epoll_obj.register(cs.fileno(), select.EPOLLIN)
str=""
while 1:
    readylist = epoll_obj.poll()
    for fd,event in readylist:
        if fd == cs.fileno() and event & select.EPOLLIN:
            buf = cs.recv(128)
            if not len(buf):
                cs.close()
                break
            print "cli: ", buf

        if fd == cs.fileno() and event & select.EPOLLOUT:
            cs.send(str)
            epoll_obj.modify(cs.fileno(), select.EPOLLIN)

        if fd == sys.stdin.fileno() and event&select.EPOLLIN:
            str=raw_input("me:")
            epoll_obj.modify(cs.fileno(), select.EPOLLOUT)