Interesting. Running gpsd in debug mode shows me:
gpsd -nND 4 udp://
255.255.255.255:6125gpsd:INFO: launching (Version 3.19)
gpsd:INFO: listening on port gpsd
gpsd:PROG: NTP: shmat(0,0,0) succeeded, segment 0
gpsd:PROG: NTP: shmat(1,0,0) succeeded, segment 1
gpsd:PROG: NTP: shmat(2,0,0) succeeded, segment 2
gpsd:PROG: NTP: shmat(3,0,0) succeeded, segment 3
gpsd:PROG: NTP: shmat(4,0,0) succeeded, segment 4
gpsd:PROG: NTP: shmat(5,0,0) succeeded, segment 5
gpsd:PROG: NTP: shmat(6,0,0) succeeded, segment 6
gpsd:PROG: NTP: shmat(7,0,0) succeeded, segment 7
gpsd:PROG: successfully connected to the DBUS system bus
gpsd:PROG: shmget(0x47505344, 20816, 0666) for SHM export succeeded
gpsd:PROG: shmat() for SHM export succeeded, segment 8
gpsd:INFO: stashing device udp://
255.255.255.255:6125 at slot 0
gpsd:PROG: no /etc/gpsd/device-hook present, skipped running ACTIVATE hook
gpsd:INFO: opening UDP feed at 255.255.255.255, port 6125.
gpsd:INFO: gpsd_activate(2): activated GPS (fd 6)
gpsd:INFO: PPS:udp://
255.255.255.255:6125 ntpshm_link_activate: 1
gpsd:INFO: device udp://
255.255.255.255:6125 activated
gpsd:INFO: running with effective group ID 20
gpsd:INFO: running with effective user ID 65534
gpsd:INFO: startup at 2023-02-15T20:43:22.000Z (1676493802)
gpsd:PROG: switching to match packet type 1: $GPRMC,204323,A,5254.6976,N,00127.6425,W,0.02,305.32,150223,,,A,V*17\x0d\x0a
gpsd:PROG: switch_driver(NMEA0183) called...
gpsd:PROG: selecting NMEA0183 driver...
gpsd:INFO: udp://
255.255.255.255:6125 identified as type NMEA0183, 1 sec @ 0bps
gpsd:PROG: => Probing for Garmin NMEA
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 0
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493803.000000000 @ 1676493803.151867593
gpsd:PROG: => Probing for SiRF
gpsd:PROG: => Probing for FV-18
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
gpsd:PROG: tagged GGA as a cycle ender. 0x100000
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493804.000000000 @ 1676493804.171680860
gpsd:PROG: => Probing for Trimble Copernicus
gpsd:PROG: GPGGA ends a reporting cycle.
gpsd:PROG: => Probing for Evermore
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493805.000000000 @ 1676493805.151296342
gpsd:PROG: => Probing for GPSClock
gpsd:PROG: GPGGA ends a reporting cycle.
gpsd:PROG: => Probing for Ashtech
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493806.000000000 @ 1676493806.181353876
gpsd:PROG: => Probing for UBX
gpsd:PROG: => GPS: UBX class: 06, id: 00, len: 0, crc: 0618
gpsd:PROG: GPGGA ends a reporting cycle.
gpsd:PROG: => Probing for MediaTek
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493807.000000000 @ 1676493807.131408366
gpsd:PROG: => Probing for Javad GREIS
gpsd:PROG: GPGGA ends a reporting cycle.
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493808.000000000 @ 1676493808.151297129
gpsd:PROG: GPGGA ends a reporting cycle.
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
gpsd:PROG: NTP: ntpshm_put(udp://
255.255.255.255:6125,-20) 1676493809.000000000 @ 1676493809.141298758
gpsd:PROG: GPGGA ends a reporting cycle.
gpsd:PROG: GPRMC starts a reporting cycle. lasttag 20
So working fine - but no sign of the GSV messages
tcpdump for the incoming UDP broadcast shows:
20:56:15.150536 IP (tos 0x0, ttl 64, id 26061, offset 0, flags [none], proto UDP (17), length 144)
10.212.1.156.4997 > 255.255.255.255.6125: [udp sum ok] UDP, length 116
E...e...@..!
............|..NMEA message
$GPGGA,205615,5254.6972,N,00127.6427,W,1,12,0.5,52.9,M,47.5,M,,0000*64
..............................
20:56:15.170444 IP (tos 0x0, ttl 64, id 26062, offset 0, flags [none], proto UDP (17), length 144)
10.212.1.156.4997 > 255.255.255.255.6125: [udp sum ok] UDP, length 116
E...e...@..
............|..NMEA message
$GPGSV,3,1,10,01,42,265,46,03,06,210,41,08,68,159,53,10,38,055,48,0*6A................................
The first message - GPGGA - seems to be parsed fine.
The second, GSV, seems to be ignored.
Looking at the traffic in wireshark, each of the GPGGA sentances ends with 0x0d 0x0a
The GSV sentances terminate only with 0x0d
It seems likely you are expecting two bytes, and not getting them, for the GSV messages....
I wonder why they are not being sent. I may have to investigate the source!
0000 ff ff ff ff ff ff 00 21 32 01 e0 cf 08 00 45 00 .......!2.....E.
0010 00 90 50 6c 00 00 40 11 1d 82 0a d4 01 9c ff ff ..Pl..@.........
0020 ff ff 13 85 17 ed 00 7c 7f df 4e 4d 45 41 20 6d .......|..NMEA m
0030 65 73 73 61 67 65 0d 0a 24 47 50 52 4d 43 2c 32 essage..
$GPRMC,20040 30 34 38 30 38 2c 41 2c 35 32 35 34 2e 36 39 37
04808,A,5254.6970050 39 2c 4e 2c 30 30 31 32 37 2e 36 34 32 36 2c 57
9,N,00127.6426,W0060 2c 30 2e 30 31 2c 33 30 35 2e 33 32 2c 31 35 30
,0.01,305.32,1500070 32 32 33 2c 2c 2c 41 2c 56 2a 31 41
0d 0a 00 00
223,,,A,V*1A....
0080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ..............
0000 ff ff ff ff ff ff 00 21 32 01 e0 cf 08 00 45 00 .......!2.....E.
0010 00 90 50 6f 00 00 40 11 1d 7f 0a d4 01 9c ff ff ..Po..@.........
0020 ff ff 13 85 17 ed 00 7c 53 4e 4e 4d 45 41 20 6d .......|SNNMEA m
0030 65 73 73 61 67 65 0d 0a 24 47 50 47 53 56 2c 33 essage..$GPGSV,3
0040 2c 32 2c 31 32 2c 31 34 2c 32 34 2c 33 31 34 2c ,2,12,14,24,314,
0050 33 38 2c 31 36 2c 30 32 2c 31 37 37 2c 32 31 2c 38,16,02,177,21,
0060 32 31 2c 36 37 2c 32 37 30 2c 34 39 2c 32 32 2c 21,67,270,49,22,
0070 2c 2c 34 33 2c 30 2a 35 33 0d 00 00 00 00 00 00 ,,43,0*53.......
0080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ..............