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Old 02-10-2010, 06:09 PM   #1
Registered: May 2009
Posts: 43

Rep: Reputation: 15
question about python and sockets.. as the accept line() exacutes program hangs

ok so my question here is i wrote a simple chat type like thing to just see if what i read was working.. anyway

on the server side once it hits the
clientsocket, address = serversocket.accept()
pythonwin dosent respond untill i actually connect with the client
its a TCP based socket SOCK_STREAM

it doest the same thing when i do it under linux as well

so i guess im just wonder is it because im using TCP that its hanging? is it waiting for the connection? could this be eliminated using udp or is their a way that i could check if a client was trying to connect and if not exacute more commands and then come back to check again after so long like a compare a count variable in a loop or something
any help is much appreciated
Old 02-10-2010, 07:32 PM   #2
Registered: Jan 2010
Location: the universe
Distribution: Slackware (modified), Slackware64 (modified), openSuSE (modified)
Posts: 342

Rep: Reputation: 62
I do not know the python API well, but the socket calls will be wrapped to c library calls, which I know well.

If a socket is created using PF_INET and SOCK_STREAM it will be a TCP socket. By default each socket is in a blocking mode. This means if no input is available, the systemcall will block until there is some available. To remove this flag you can use the fcntl syscall (F_SETFL) (see fcntl(2)). In this mode the accept call will simply return if there is no connection request with EAGAIN.

Another method is to poll the socket for input using poll(2).

I hope this helps, although it does not show how to implement it in python.


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