Re: gpsd tcp NMEA feed

[Nick Taylor]

Hi again

Reran my test with newer client:
Linux TSB-168 5.4.106-itb3.04 #1 PREEMPT Tue Jul 26 13:39:10 BST 2022 
armv7l GNU/Linux

Exact same result

Best

Nick


On 26/09/2022 15:58, Nick Taylor wrote:
> Hi Frank
>
> Sorry for the incomplete report...
>
> On 26/09/2022 14:59, Frank Nicholas wrote:
> > Hello Nick,
> >
> > Gary’s probably going to need more information:
> > 1. Version of GPSD on both client & server?
> Both are:
> gpsd: 3.24.1~dev (revision release-3.24-266-g371949e15)
>
> > 2. Where was GPSD obtained from:  Linux distro, tarball binary (from 
> > where?), or compiled from source?
> Compiled from recent git head
> > 3. Is systemd involved on the client or server?
> Normally yes, but I am running gpsd in debug mode from command line
> > 4. What OS & version are you running GPSD on?
> We're still running debian stretch!!
>
> Linux TSB-318 4.4.19-itb2.02 #1 PREEMPT Fri Feb 4 18:18:14 UTC 2022 
> armv7l GNU/Linux
>
> I'm well aware that this is rather old - will rerun test with client 
> on bullseye 5.4.106 (I assume that it's a client side issue so server 
> can stay on the older kernel)
>
> Best
>
> Nick
> > > On Sep 26, 2022, at 7:13 AM, Nick Taylor <nicktaylor@dataskill.uk> 
> > > wrote:
> > >
> > > Hey Gary
> > >
> > > You may recall in the dim and distant past we hassled you for a 
> > > change to make the tcp NMEA feed option more reliable and 
> > > resilient... It has taken us a long long time to get approval to 
> > > test this on our customer installations but we are now able to see 
> > > how the option performs in the real world.
> > >
> > > For some reason the feed works fine for a while and then gpsd stops 
> > > receiving feed - even though we can verify feed using telnet. I have 
> > > managed to setup a fail situation which may or may not be similar to 
> > > what's happening in the field, however I think this is still a valid 
> > > case where it would be nice if gpsd could reconnect to the feed.
> > >
> > > My test setup is as follows:
> > >
> > > Machine A running std gpsd with feed from hardware device
> > >
> > > Create tcp feed from machine A as per your docs:
> > > socat EXEC:'gpspipe -r' TCP-LISTEN:2948,reuseaddr,fork
> > >
> > > Machine B run gpsd in debug mode:
> > > gpsd -D5 -n -N tcp://192.168.2.53:2948
> > >
> > > All good so farnow interrupt the feed from machine A as follows:
> > > iptables -I OUTPUT -d 192.168.2.52 -j DROP; sleep 1200; iptables -D 
> > > OUTPUT -d 192.168.2.52 -j DROP
> > >
> > > Machine A we see this:
> > > 2022/09/26 09:55:07 socat[16311] E write(7, 0x7f674db0, 8192): 
> > > Connection timed out
> > >
> > > gpsd log on machine B loops as follows:
> > > gpsd:PROG: CORE: pselect: timeout
> > > gpsd:PROG: checking client(0)
> > > gpsd:CLIENT: <= client(0): ?WATCH={"enable":true,"json":true};
> > >
> > > gpsd:PROG: awaken(0) fd 7, path tcp://192.168.2.53:2948
> > > gpsd:PROG: device 0 (fd=7, path tcp://192.168.2.53:2948) already 
> > > active.
> > > gpsd:CLIENT: => client(0) len 278: 
> > > {"class":"DEVICES","devices":[{"class":"DEVICE","path":"tcp://192.168.2.53:2948","driver":"NMEA0183","a
> > > ctivated":"2022-09-26T09:37:29.345Z","flags":1}]}
> > > {"class":"WATCH","enable":true,"json":true,"nmea":false,"raw":0,"scaled":false,"timing":false,"split24":false,"pps":false} 
> > >
> > >
> > > gpsd:PROG: CORE: pselect: timeout
> > > gpsd:PROG: gpsd_multipoll(7) DEVICE_UNCHANGED for 5
> > > gpsd:PROG: checking client(0)
> > > gpsd:CLIENT: <= client(0): ?WATCH={"enable":true,"json":true};
> > >
> > > gpsd:PROG: awaken(0) fd 7, path tcp://192.168.2.53:2948
> > > gpsd:PROG: device 0 (fd=7, path tcp://192.168.2.53:2948) already 
> > > active.
> > > gpsd:CLIENT: => client(0) len 278: 
> > > {"class":"DEVICES","devices":[{"class":"DEVICE","path":"tcp://192.168.2.53:2948","driver":"NMEA0183","a
> > > ctivated":"2022-09-26T09:37:29.345Z","flags":1}]}
> > > {"class":"WATCH","enable":true,"json":true,"nmea":false,"raw":0,"scaled":false,"timing":false,"split24":false,"pps":false} 
> > >
> > >
> > > gpsd:PROG: CORE: pselect: timeout
> > > gpsd:PROG: checking client(0)
> > > gpsd:CLIENT: <= client(0): ?WATCH={"enable":true,"json":true};
> > >
> > > gpsd:PROG: awaken(0) fd 7, path tcp://192.168.2.53:2948
> > > gpsd:PROG: device 0 (fd=7, path tcp://192.168.2.53:2948) already 
> > > active.
> > > gpsd:CLIENT: => client(0) len 278: 
> > > {"class":"DEVICES","devices":[{"class":"DEVICE","path":"tcp://192.168.2.53:2948","driver":"NMEA0183","a
> > > ctivated":"2022-09-26T09:37:29.345Z","flags":1}]}
> > > {"class":"WATCH","enable":true,"json":true,"nmea":false,"raw":0,"scaled":false,"timing":false,"split24":false,"pps":false} 
> > >
> > >
> > > Feed can be seen on machine B using telnet, but it seems gpsd 
> > > doesn't notice the failed connection and the only way I found to 
> > > recover is to restart gpsd
> > >
> > > Your input would be much appreciated
> > >
> > > Thanks and regards
> > >
> > > Nick