[MUD-Dev] randomly dropped connections

Ben Greear greearb at candelatech.com
Fri Mar 3 00:18:04 New Zealand Daylight Time 2000


cg at ami-cg.GraySage.Edmonton.AB.CA wrote:
> 
> [Matthew Mihaly <diablo at best.com>:]
> 
> > I have been having a rather serious problem lately with Achaea, and we are
> > relatively baffled. What is happening is that players are spontaneously
> > getting their links cut. This cannot be the fault of our code (which is
> > interpreted by the vortex engine), as we don't have the power to cut
> > someone's link in this manner (Basically, they lose their link, and then
> > our routine which cycles through looking for players with lost connections
> > ditches the player). It's happened to me a few times, and, when telnetting
> > straight from a linux prompt, the only message I receive is the
> > "connection cut by foreign host" (or something similar). The weird thing
> > is that it seems to 'follow' a character around for a bit. It COULD be our
> > vortex engine, but the author of it assures me he's not touched anything
> > to do with networking for over a year.
> >
> > Something JC said in his post about network setups made me wonder if maybe
> > our ISP (mudservices) has a bad piece of hardware. Could a faulty router
> > or something be causing this sort of problem?
> 
> I'm not a networking expert, so hopefully you'll get some replies from
> some of them. However, the one thing that occurs to me is to find out
> what you are seeing at your end. One way would be to get the author of
> Vortex to put some debugging stuff in, to show the reasons for any
> disconnection. If both ends of the connection see the equivalent of
> "connection dropped by other end", then it sure looks like your ISP or
> something.
> 
> Another way would be to put some kind of network tester box between your
> host machine and the network connection. It should be able to see which
> end is triggering the disconnect. From what I know of TCP/IP, such a
> box should exist, but I don't know of any in particular. They won't
> be cheap, so you would have to borrow one. Actually, a cheap PC with
> a pair of ethernet cards could do the job, but I don't know if software
> to handle it exists out there.

Actually, they are pretty cheap.  Get a pc, and run something like tcpdump,
or ethereal.  (This assumes you're running linux...)  If you have windows,
netxray is good, if very expensive.)

Also, you only need one NIC, just a hub to plug it into (that is also
plugged into your server of course.)  A ether-switch will NOT work for
snooping like this...  If you are fast, you can probably pull the link,
insert the hub, and re-connect fast enough to not lose too many connections :)

Put filters on to grab every IP pkt going between the two endpoint IP
addresses, and watch it go.  If it isn't obvious, if you can post a
log, or send it to me, I might be able to offer some help...

Ben

> 
> --
> Don't design inefficiency in - it'll happen in the implementation.
> 
> Chris Gray     cg at ami-cg.GraySage.Edmonton.AB.CA
>                http://www.GraySage.Edmonton.AB.CA/cg/
> 
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--
Ben Greear (greearb at candelatech.com)  http://scry.wanfear.com/~greear 
Author of ScryMUD:  scry.wanfear.com 4444        (Released under GPL)
http://scry.wanfear.com



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