MQTT Authentication not implemented? username and password not being picked up

[dw-1983]

Firstly, what I can see from the documentation - great work! I have tried different gateways and none provides the flexibility I see here to bulk read and write multiple registers from/to a modbus slave in combination of mapping this functionality to MQTT topics.

My use case:

• Read sensor data (holding registers) contained in multiple subsequent register-blocks from a Sugar Valley Pool Controller and (same modbus line) a HE200 VFD Inverter for filte rpump motor controlling
• Write holding registers to both components for starting/stopping filtering, setting pump motor speed, etc. I have the special need to write a single register value using Function 16 (0x10, write_multiple_holding_register), as the component does not accept/react to a single register write operation (at least for a special register) when writing a value of 0. Maybe I will raise another issue for this case, currently I can help myself in writing the following register, too, to force a write_multiple.

My current setup:

• I am running a mosquitto broker/server on OpenWRT using the OOTB user/password authentication using passwd file. Connection to the broker runs fine since several years using user/passwd from different clients like tasmota, MQTTX and HA.
• I am running the latest mqmgateway in a docker container using the host network on QNAP NAS stotrage (Container Station)

The Issue:

• The gateway comes up fine in the logs and connects to the broker. The connection is listed in the mosquitto logs of the server broker. After connecting, the server immediately closes the connection due to missing authentication.

My mqtt configuration snippet for mqmgateway:

mqtt:  
  client_id: 'modbus'  
  refresh: 1s  
  broker:  
    host: 192.168.2.1  
    port: 1883  
    keepalive: 60  
    username: '<masked username>'  
    password: '<masked password>'

The logs of the gateway look like this:

2023-Sep-22 11:45:46.199642: [INFO]     modmqttd is starting  
2023-Sep-22 11:45:46.248124: [INFO]     Added converter plugin std  
2023-Sep-22 11:45:46.327991: [INFO]     Connecting to 192.168.2.208:8899  
2023-Sep-22 11:45:46.328252: [INFO]     modbus: connecting  
2023-Sep-22 11:45:46.329952: [INFO]     modbus: connected  
2023-Sep-22 11:45:46.330161: [INFO]     Waiting for mqtt network to become online  
2023-Sep-22 11:45:46.351543: [INFO]     Connecting to 192.168.2.1:1883  
2023-Sep-22 11:45:46.351816: [INFO]     Waiting for mqtt network to become online  
2023-Sep-22 11:45:46.361430: [INFO]     Connection estabilished  
2023-Sep-22 11:45:46.361664: [INFO]     Mqtt conected, sending subscriptions...  
2023-Sep-22 11:45:46.361845: [INFO]     Mqtt ready to process messages  
2023-Sep-22 11:45:46.361976: [INFO]     Disconnected from mqtt broker, code:The connection was refused.  
2023-Sep-22 11:45:46.362084: [INFO]     reconnecting to mqtt broker  
2023-Sep-22 11:45:46.449680: [INFO]     Disconnected from mqtt broker, code:The connection was lost.  
2023-Sep-22 11:45:46.449902: [INFO]     reconnecting to mqtt broker

The logs of the broker server look like this:

Fri Sep 22 13:21:48 2023 daemon.notice mosquitto[30795]: 1695381708: New connection from 192.168.2.202:49910 on port 1883.  
Fri Sep 22 13:21:48 2023 daemon.debug mosquitto[30795]: 1695381708: Sending CONNACK to modbus (0, 5)  
Fri Sep 22 13:21:48 2023 daemon.notice mosquitto[30795]: 1695381708: Client modbus disconnected, not authorised.

It looks like the mqtt client does not use credentials at all, as successful user/pass connection attempts look like this:

Fri Sep 22 13:21:43 2023 daemon.notice mosquitto[30795]: 1695381703: New connection from 192.168.3.178:16281 on port 1883.  
Fri Sep 22 13:21:43 2023 daemon.notice mosquitto[30795]: 1695381703: New client connected from 192.168.3.178:16281 as DVES_XXXX (p2, c1, k15, u'USERNAME_MASKED')

As far as I can see from the code, mosquitto_username_pw_set is not being called prior to mosquitto_connect. As I am no C++ developer, I don't trust myself to provide a PR (and have no dev environment setup, atm). Would you mind having a look at this issue? I will provide additional logs and do testing as required, of course.

[BlackZork]

Write holding registers to both components for starting/stopping filtering, setting pump motor speed, etc. I have the special need to write a single register value using Function 16 (0x10, write_multiple_holding_register), as the component does not accept/react to a single register write operation (at least for a special register) when writing a value of 0. Maybe I will raise another issue for this case, currently I can help myself in writing the following register, too, to force a write_multiple.

That is interesting. Unfortunately mqmgateway uses write_multiple_holding_register only when number of register to write is > 1. Do do this you have to specify count: (2 or more) in config for command topic.

I am not sure what you mean at the end, you have workaround for this problem? Only one I can think of is to read at least two adjacent registers and write ["0","(last value]".

[dw-1983]

Thanks for the fast fix! I see there is a docker pipeline set up, so probably the docker repo will auto-update at some time later?

Regarding my custom write_multiple case:

• Yes, my workaround currently is to write the target and the following register.
• I have seen implementations where you have a flag "write_type" (or register_type, in your implementation), which could be set to holdings (plural) and force a write_multiple_holding_register despite having a register count of 1.

Currently that workaround is working fine, because the followup register holds a binary value (that states "having heating installed" or not), which is always static (0) for my setup.

[BlackZork]

Thanks for the fast fix! I see there is a docker pipeline set up, so probably the docker repo will auto-update at some time later?

Unfortunately I do not have docker image build setup yet. There is a pull request #28, but it is not merged yet.

[dw-1983]

@BlackZork just fyi, I finally managed to set up a linux targeting c++ dev environment and able to build the binaries and a docker container. After starting up the service, everything worked out fine right away (mqtt connection, modbus register read/write). Especially the automatic register grouping is a huge boost of performance and minimizes the configuration effort on my integration path into Home Assistant. Incomparable to the native modbus implementation in HA (pymodbus-based). Thanks again for your work!

[BlackZork]

Good to know that it works for you, thanks :-)

[git-developer]

FYI: v1.2.0 is available as Docker image ckware/mqmgateway:v1.2.0 on Docker Hub.