Venus-signalk MQTT connection

Modifications
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Title:
MQTT on LAN (Cerbo GX v3.72) – connection refused / inconsistent interfaces / SignalK integration

Description:

I’m trying to set up a local (LAN) MQTT connection between a Cerbo GX and a SignalK server (Raspberry Pi), as a more robust alternative to the existing VRM integration.

Current setup:

  • Device: Victron Cerbo GX MK2

  • Firmware: v3.72

  • MQTT access: enabled (Settings → Services → MQTT Access ON)

  • Local network security profile: tested (currently verifying Secured vs Unsecured)

  • Multiple IP addresses on Cerbo:

    • 192.168.1.101

    • 192.168.1.102

    • 192.168.1.105

Goal:

  • Direct local MQTT (LAN) integration with SignalK

  • Using signalk-venus-plugin in MQTT mode (instead of VRM)

Problem:

  • MQTT connection on port 1883 results in:

    ECONNREFUSED

  • Tested from Raspberry Pi with:

    mosquitto_sub -h 192.168.1.102 -t "N/#" -v
mosquitto_sub -h 192.168.1.101 -t "N/#" -v
mosquitto_sub -h 192.168.1.105 -t "N/#" -v

Results:

  • Some IPs → connection refused

  • Some IPs → connection established but no data received

  • Additionally, the signalk-venus-plugin keeps reverting to:

    tcp:host=...,port=78

    (D-Bus over TCP), even when MQTT is explicitly configured

What I already tried:

  • Enabled/disabled MQTT access

  • Rebooted Cerbo GX

  • Cleared all plugin settings (no VRM, no D-Bus)

  • Adjusted local network security profile

  • Tested all available Cerbo IP addresses

  • Verified network connectivity (ping/SSH OK)

Questions:

  1. On which interface/IP does the Cerbo GX MQTT broker actually listen?

  2. Is port 1883 still available in Venus OS v3.72, or only TLS (8883)?

  3. Is a specific “Local network security profile” required for plaintext MQTT?

  4. Is it expected behavior that MQTT connections are accepted but no data is published?

  5. Can the presence of D-Bus TCP (port 78) cause clients/plugins to fall back automatically?

  6. What is the recommended way to reliably use local MQTT (LAN) instead of VRM?

Additional context:

  • VRM integration via signalk-venus-plugin works perfectly

  • Goal is redundancy: local MQTT + VRM fallback

  • Network is stable and functioning correctly

Any insights would be highly appreciated, especially regarding MQTT behavior in recent Venus OS versions.

Thanks!