Date: Fri, 9 Nov 2007 11:18:31 +0200 From: Nikos Vassiliadis <nvass@teledomenet.gr> To: freebsd-questions@freebsd.org Cc: Bram <bram@diomedia.be> Subject: Re: TCP/IP questions Message-ID: <200711091118.31621.nvass@teledomenet.gr> In-Reply-To: <47333C1A.7070709@diomedia.be> References: <4731E1A4.6020809@diomedia.be> <200711081408.22387.nvass@teledomenet.gr> <47333C1A.7070709@diomedia.be>
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On Thursday 08 November 2007 18:40:58 Bram wrote: > Nikos Vassiliadis schreef: > > On Wednesday 07 November 2007 18:02:44 Bram wrote: > >> Hi all, > >> > >> Can you change the timeout for a tcp connection ? > >> I need to do the following: start a tcp connection , unplug the > >> network cable (it's actually wifi but the effect is the same),send > >> some data over the connection,wait 20 seconds , reinsert the network > >> cable and just keep working. > >> When you normally do this the connection will be dead. > >> Is there a way in freebsd to change this ? are there parameters wich > >> you can set so that the above would work (20 seconds without network > >> can happen) ? > > > > TCP using the default FreeBSD settings, can survive > > 20 secs of inactivity. It can be an application forced > > timeout. What application/protocol are talking about? > > > > Nikos > > This is the more full explanation: > > I have setup a mobile pc to roam across our building. > By reducing the dwell time and changing the channel list to only the > channels I use roaming now works within ten seconds en sometimes within > one or two seconds. > The previous configuration was with fedora and there I was unable to get > roaming time under 25 seconds. > > I do have one very annoying problem however and I have no idea how to > solve it. > The software uses psycopg (a python postgresql module) wich uses the > standard system parameters for connections (At least that is what I > think). -On fedora if the connection gets lost and it takes 30 seconds > to remake a new connection operation is not interupted, after the 30 > seconds you get the data you've been waiting for. > -On freebsd however we get it a lot that the connection is "lost", you > can easily start a new connection wich works fine, but the old > connection you wore using stops working and the app. hangs (If I had to > guess I would say that roaming works about 95% of the time and the > connection is lost about 5% of the time). > > I also get a lot of IFDOWN IFUP messages but this seems normal to me. > > I am now going to program something in twisted using udp to see if this > works better. If your app is using SO_KEEPALIVE, you can increase sysctl net.inet.tcp.keepintvl. You could also trace the application to see what's going on. Something like: ktrace -i $application Nikos
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