[ntp:questions] How to get shared memory access from gpsd to ntpd to work?

Etaoin Shrdlu etaoin at clickworkorange.com
Tue Aug 22 14:14:06 UTC 2017

On Tue, 2017-08-22 at 08:50 -0400, Charles Elliott wrote:
> For one thing, 10110 may be the wrong port number to use: "The
> registered ports are those from 1024 through 49151. IANA maintains
> the official list of well-known and registered ranges.[3] The dynamic
> or private ports are those from 49152 through 65535. One common use
> for this range is for ephemeral ports."
> (https://en.wikipedia.org/wiki/Port_(computer_networking))  Second,
> port 10110 may be reserved for NMEA-0183 Navigational Data (on GPS
> devices).  See https://www.iana.org/assignments/service-names-port-
> numbers/service-names-port-numbers.xhtml?
> <https://www.iana.org/assignments/service-names-port-numbers/service-
> names-port-numbers.xhtml?&page=117> &page=117.  You might want to
> consider a port number in [49152, 65535] on, if that
> is your computer’s IP address.  I am referring to these error
> messages:

Fine, but it does work - how else would gpsmon be able to show all the
data? Did you see my initial message? I have already confirmed long ago
that gpsd has no trouble receiving and parsing the incoming UDP. The
problem is getting the data from gpsd to ntpd. 

> I agree with the person who wrote that he had never heard of
> accessing a GPS device with UDP; NTPD is not set up for that,
> although using shared memory may be a good workaround.  I am not so
> sure of the PPS signal coming in that way though.  NTPD is set to
> detect PPS from the rising or falling edge of a single RS-232 port
> pin, DCD if I recall correctly.
> Charles Elliott

More information about the questions mailing list