tcp networking question (CLOSE_WAIT)

Ray rui.vapps at gmail.com
Thu Feb 25 12:55:49 EST 2016


hi,

I'm new to python networking. I am waiting TCP server/client app by using python built-in SocketServer. My problem is if client get killed, then the tcp port will never get released, in CLOSE_WAIT

maybe I didn't do the handler right? or anyway I can catch the client get killed?

I wrote following simple code to explain the issue I have, server listen on 127.0.0.1:1234
client need to send multi-messages (I am sending 2 in this test) if client get killed (I just do kill client_pid) then if I check lsof, I will see the new allocated tcp do not get released 

########server.py########

#!/usr/bin/python
import threading
import SocketServer
import time

class TCPServerRequestHandler(SocketServer.BaseRequestHandler):

    def handle(self):
        while True:
            data=self.request.recv(1024)
            if not data:
                time.sleep(0.1)
                continue
            print data
            self.request.send(data)
            if data=='end':
                break

def main():
    server = TCPServer(('127.0.0.1', 1234), TCPServerRequestHandler)
    ip, port = server.server_address
    server_thread = threading.Thread(target=server.serve_forever)
    server_thread.daemon = True
    server_thread.start()
    time.sleep(600)
    server.shutdown()
    server.server_close()
if __name__=='__main__':
    main()

########client.py########
import socket
import time

def client():
    sock=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect(('127.0.0.1', 1234))
    sock.sendall('hello')
    response=sock.recv(1024)
    print "Received:", response
    time.sleep(60)
    sock.sendall('end')
    response=sock.recv(1024)
    print "Received:", response
    sock.close()

if __name__=='__main__':
    client()


when I run it, client has 60 seconds sleep, so I just kill the process from OS
kill 93948

then I'm running lsof to find my TCP/UDP 
lsof -n -p $(ps -ef|grep serve[r]|awk '{print $2}')|egrep '(TCP|UDP)'|awk '{print $NF}'

TCP 127.0.0.1:search-agent (LISTEN)
TCP 127.0.0.1:search-agent->127.0.0.1:59411 (CLOSE_WAIT)

I will see the CLOSE_WAIT, this is where the client get killed.


any help would be great!

Thanks a lot!
 


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