StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POHow epoll detect clientside close in Python?
text
Body
copied!<p><strong>Here is my server</strong></p> <pre><code>"""Server using epoll method""" import os import select import socket import time from oodict import OODict addr = ('localhost', 8989) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) s.bind(addr) s.listen(8) s.setblocking(0) # Non blocking socket server epoll = select.epoll() epoll.register(s.fileno(), select.EPOLLIN) # Level triggerred cs = {} data = '' while True: time.sleep(1) events = epoll.poll(1) # Timeout 1 second print 'Polling %d events' % len(events) for fileno, event in events: if fileno == s.fileno(): sk, addr = s.accept() sk.setblocking(0) print addr cs[sk.fileno()] = sk epoll.register(sk.fileno(), select.EPOLLIN) elif event & select.EPOLLIN: data = cs[fileno].recv(4) print 'recv ', data epoll.modify(fileno, select.EPOLLOUT) elif event & select.EPOLLOUT: print 'send ', data cs[fileno].send(data) data = '' epoll.modify(fileno, select.EPOLLIN) elif event & select.EPOLLERR: print 'err' epoll.unregister(fileno) </code></pre> <p><strong>client side input</strong></p> <pre><code>ideer@ideer:/home/chenz/source/ideerfs$ telnet localhost 8989 Trying ::1... Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 123456 123456 ^] telnet> q Connection closed. </code></pre> <p><strong>server side output</strong></p> <pre><code>ideer@ideer:/chenz/source/ideerfs$ python epoll.py Polling 0 events Polling 0 events Polling 1 events ('127.0.0.1', 53975) Polling 0 events Polling 1 events recv 1234 Polling 1 events send 1234 Polling 1 events recv 56 Polling 1 events send 56 Polling 0 events Polling 0 events Polling 0 events Polling 1 events recv Polling 1 events send Polling 1 events recv Polling 1 events send Polling 1 events recv Polling 1 events send Polling 1 events recv ^CTraceback (most recent call last): File "epoll.py", line 23, in <module> time.sleep(1) KeyboardInterrupt </code></pre> <p>It's strange that after the client has closed the connection, epoll still can poll recv and send events! Why does EPOLLERR event never happen? it's the same if you use EPOLLHUP.</p> <p>I notice that the EPOLLERR event only happens when you try to write a closed connection. Besides this, is there another way to tell that whether the connection has been closed or not?</p> <p>Is it correct to treat the connection as closed if you get nothing in a EPOLLIN event?</p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload