threads and socket question

**Daniel T.** · Jul 18 '05, 02:10 AM

Re: threads and socket question

Gon?alo Rodrigues <op73418@mail.t elepac.pt> wrote:
[color=blue]
> My setup is the following: I have socket s from which I want to read
> and write. So I made the following set up:
>
> There is a thread whose only job is to read. Any data read (from recv
> call) is just passed to (some) Queue. This thread is "owned" by a
> second thread waiting on a Queue for write requests. The thread just
> pops these from the Queue, and calls the send method from the socket.
> This thread also takes care of closing the socket or (possibly)
> handling any exceptions raised due to socket operation.
>
> So my question is: since I have two threads sharing the same socket,
> even though one is only reading and the other does everything else, do
> I have to watch out for any "concurrenc y" issues?
>
> P.S: This is for learning experience. So it's of no use telling me
> that I should learn Twisted :-) I may (eventually) get there, but at
> the moment I feel more omfortable with working with plain blocking
> sockets.[/color]

The first problem I can think of is the one that stopped me. Note the
code below... You can't close a blocked socket in python even from a
separate thread.

import unittest
import socket
import threading
import time

class SocketAcceptor ( threading.Threa d ):
def __init__( self, socket ):
threading.Threa d.__init__( self )
self.socket = socket
self.done = 0

def run( self ):
self.socket.bin d( ( "", 3424 ) )
self.socket.lis ten( 5 )
try:
child, ip = self.socket.acc ept()
except:
pass
self.done = 1

class SocketTester ( unittest.TestCa se ):
def testClose( self ):
ss = socket.socket()
acceptor_thread = SocketAcceptor( ss )
acceptor_thread .start()
time.sleep( 1 )
ss.close()
time.sleep( 1 )
self.assertEqua ls( acceptor_thread .done, 1 )

if __name__ == '__main__':
unittest.main()

**Gonçalo Rodrigues** · Jul 18 '05, 02:12 AM

Re: threads and socket question

On Mon, 01 Sep 2003 01:34:32 GMT, "Daniel T."
<postmaster@ear thlink.net> wrote:
[color=blue]
>Gon?alo Rodrigues <op73418@mail.t elepac.pt> wrote:
>[color=green]
>> My setup is the following: I have socket s from which I want to read
>> and write. So I made the following set up:
>>
>> There is a thread whose only job is to read. Any data read (from recv
>> call) is just passed to (some) Queue. This thread is "owned" by a
>> second thread waiting on a Queue for write requests. The thread just
>> pops these from the Queue, and calls the send method from the socket.
>> This thread also takes care of closing the socket or (possibly)
>> handling any exceptions raised due to socket operation.
>>
>> So my question is: since I have two threads sharing the same socket,
>> even though one is only reading and the other does everything else, do
>> I have to watch out for any "concurrenc y" issues?
>>
>> P.S: This is for learning experience. So it's of no use telling me
>> that I should learn Twisted :-) I may (eventually) get there, but at
>> the moment I feel more omfortable with working with plain blocking
>> sockets.[/color]
>
>The first problem I can think of is the one that stopped me. Note the
>code below... You can't close a blocked socket in python even from a
>separate thread.
>[/color]

Thanks for this piece of info. My experiences with my setup confirm
it.

I really want to keep the socket-closing in the write thread so my
problem is reduced to be able to order to read thread to die. What I
chose to do is to have it periodically check some exit flag to know
when to exit. I believe this can be done by calling select with a
timeout before the recv blocking call. Back to the docs and
Python-experimenting-mode.

With my best regards,
G. Rodrigues

threads and socket question

threads and socket question

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