Thx - just tried mirroring exactly your config, but I still get "empty queue".
Here is the debug log from the run (as you can see, I have updated to 0.54b and even included your little fix you just posted on GIT):
Apr 28 22:52:20 server systemd[1]: Started LSB: weewx weather system.
Apr 28 22:52:20 server weewx[661236] INFO user.interceptor: driver version is 0.54b
Apr 28 22:52:20 server weewx[661236] INFO user.interceptor: device type: fineoffset-bridge
Apr 28 22:52:20 server weewx[661236] INFO user.interceptor: mode is listen
Apr 28 22:52:20 server weewx[661236] INFO user.interceptor: listen on :8000
Apr 28 22:52:20 server weewx[661236] INFO user.interceptor: sensor map: {'pressure': 'pressure', 'barometer': 'barometer', 'outHumidity': 'humidity_out', 'inHumidity': 'humidity_in', 'outTemp': 'temperature_out', 'inTemp': 'temperature_in', 'windSpeed': 'wind_speed', 'windGust': 'wind_gust', 'windDir': 'wind_dir', 'windGustDir': 'wind_gust_dir', 'radiation': 'solar_radiation', 'dewpoint': 'dewpoint', 'windchill': 'windchill', 'rain': 'rain', 'rainRate': 'rain_rate', 'UV': 'uv', 'txBatteryStatus': 'wh26_battery', 'extraTemp1': 'temperature_1', 'extraTemp2': 'temperature_2', 'extraTemp3': 'temperature_3', 'extraHumid1': 'humidity_1', 'extraHumid2': 'humidity_2', 'soilTemp1': 'soil_temperature_1', 'soilTemp2': 'soil_temperature_2', 'soilMoist1': 'soil_moisture_1', 'soilMoist2': 'soil_moisture_2', 'soilMoist3': 'soil_moisture_3', 'soilMoist4': 'soil_moisture_4', 'leafWet1': 'leafwetness_1', 'leafWet2': 'leafwetness_2', 'pm2_5': 'pm2_5', 'extraTemp4': 'temperature_4', 'extraTemp5': 'temperature_5', 'extraTemp6': 'temperature_6', 'extraTemp7': 'temperature_7', 'extraTemp8': 'temperature_8', 'extraHumid3': 'humidity_3', 'extraHumid4': 'humidity_4', 'extraHumid5': 'humidity_5', 'extraHumid6': 'humidity_6', 'extraHumid7': 'humidity_7', 'extraHumid8': 'humidity_8', 'soilTemp3': 'soil_temperature_3', 'soilTemp4': 'soil_temperature_4', 'windBatteryStatus': 'wh68_battery', 'supplyVoltage': 'wh40_battery'}
Apr 28 22:52:20 server weewx[661236] DEBUG user.interceptor: start tcp server
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdTimeSynch
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdTimeSynch
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdConvert
Apr 28 22:52:20 server weewx[661236] INFO weewx.engine: StdConvert target unit is 0x1
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdConvert
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdCalibrate
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdCalibrate
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdQC
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdQC
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.wxservices.StdWXCalculate
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.manager: Daily summary version is 1.0
Apr 28 22:52:20 server weewx[661236] INFO weewx.wxservices: The following values will be calculated: pressure=prefer_hardware, barometer=prefer_hardware, altimeter=prefer_hardware, windchill=hardware, heatindex=hardware, dewpoint=prefer_hardware, inDewpoint=prefer_hardware, rainRate=hardware, maxSolarRad=prefer_hardware, cloudbase=prefer_hardware, humidex=prefer_hardware, appTemp=prefer_hardware, ET=prefer_hardware, windrun=prefer_hardware
Apr 28 22:52:20 server weewx[661236] INFO weewx.wxservices: The following algorithms will be used for calculations: altimeter=aaASOS, maxSolarRad=RS
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.wxservices.StdWXCalculate
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdArchive
Apr 28 22:52:20 server weewx[661236] INFO weewx.engine: Archive will use data binding wx_binding
Apr 28 22:52:20 server weewx[661236] INFO weewx.engine: Record generation will be attempted in 'hardware'
Apr 28 22:52:20 server weewx[661236] INFO weewx.engine: Using archive interval of 300 seconds (specified in weewx configuration)
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Use LOOP data in hi/low calculations: 1
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdArchive
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.restx.StdStationRegistry
Apr 28 22:52:20 server weewx[661236] INFO weewx.restx: StationRegistry: Station will be registered.
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.restx.StdStationRegistry
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.restx.StdWunderground
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.restx: WU essentials: {}
Apr 28 22:52:20 server weewx[661236] INFO weewx.restx: Wunderground-PWS: Data for station IHESSENR12 will be posted
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.restx.StdWunderground
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.restx.StdPWSweather
Apr 28 22:52:20 server weewx[661236] INFO weewx.restx: PWSweather: Posting not enabled.
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.restx.StdPWSweather
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.restx.StdCWOP
Apr 28 22:52:20 server weewx[661236] INFO weewx.restx: CWOP: Posting not enabled.
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.restx.StdCWOP
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.restx.StdWOW
Apr 28 22:52:20 server weewx[661236] INFO weewx.restx: WOW: Posting not enabled.
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.restx.StdWOW
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.restx.StdAWEKAS
Apr 28 22:52:20 server weewx[661236] INFO weewx.restx: AWEKAS: Data will be uploaded for user maxgutberlet
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.restx.StdAWEKAS
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdPrint
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdPrint
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Loading service weewx.engine.StdReport
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Finished loading service weewx.engine.StdReport
Apr 28 22:52:20 server weewx[661236] INFO __main__: Starting up weewx version 4.0.0b18
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.engine: Station does not support reading the time
Apr 28 22:52:20 server weewx[661236] INFO weewx.engine: Using binding 'wx_binding' to database 'weewx.sdb'
Apr 28 22:52:20 server weewx[661236] INFO weewx.manager: Starting backfill of daily summaries
Apr 28 22:52:20 server weewx[661236] INFO weewx.engine: Starting main packet loop.
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.manager: Daily summary version is 1.0
Apr 28 22:52:20 server weewx[661236] DEBUG weewx.manager: Daily summary version is 1.0
Apr 28 22:52:30 server weewx[661236] DEBUG user.interceptor: empty queue
Apr 28 22:53:30 server weewx[661236] message repeated 6 times: [ DEBUG user.interceptor: empty queue]
Apr 28 22:53:40 server weewx[661236] DEBUG user.interceptor: empty queue
Apr 28 22:53:50 server weewx[661236] DEBUG user.interceptor: empty queue
Apr 28 22:55:00 server weewx[661236] message repeated 7 times: [ DEBUG user.interceptor: empty queue]
Apr 28 22:55:10 server weewx[661236] DEBUG user.interceptor: empty queue
And here is the tcpdump at the same time that clearly shows the unit connecting to port 8000:
tcpdump -i eth0 "src 192.168.0.68 and dst port 8000"
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
22:54:15.110857 IP 192.168.0.68.6929 > server.gutberlet.org.8000: Flags [S], seq 19845874, win 5840, options [mss 1460], length 0
22:54:15.118857 IP 192.168.0.68.6929 > server.gutberlet.org.8000: Flags [P.], seq 19845875:19846415, ack 4034944965, win 5840, length 540
22:54:15.127088 IP 192.168.0.68.6929 > server.gutberlet.org.8000: Flags [F.], seq 540, ack 504, win 5337, length 0
22:55:19.115660 IP 192.168.0.68.22747 > server.gutberlet.org.8000: Flags [S], seq 19957218, win 5840, options [mss 1460], length 0
22:55:19.141821 IP 192.168.0.68.22747 > server.gutberlet.org.8000: Flags [P.], seq 19957219:19957759, ack 732863350, win 5840, length 540
22:55:19.149284 IP 192.168.0.68.22747 > server.gutberlet.org.8000: Flags [F.], seq 540, ack 504, win 5337, length 0
22:56:23.112251 IP 192.168.0.68.40696 > server.gutberlet.org.8000: Flags [S], seq 20072022, win 5840, options [mss 1460], length 0
22:56:23.120399 IP 192.168.0.68.40696 > server.gutberlet.org.8000: Flags [P.], seq 20072023:20072563, ack 292068405, win 5840, length 540
22:56:23.128518 IP 192.168.0.68.40696 > server.gutberlet.org.8000: Flags [F.], seq 540, ack 504, win 5337, length 0
Same things happen when I do wu-client sniff - I clearly see the packages going to WU in the tcpdump but nothing ever pops up in interceptor.
Looks like something is broken when actually queuing the packets - I was already suspecting something like apparmor to interfere but I am not seeing