Re: gpsd tcp NMEA feed

[Nick Taylor]

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