TCP/IP questions

Bram bram at
Thu Nov 8 08:41:12 PST 2007

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.

kind regards

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