Subscribe to a topic with TIcsMQTTClient

[Alberto Fornés 22]

Hi, I have a Mosquitto server that publishes messages and I can subscribe to it using programs like MQTT Explorer. By testing with TIcsMQTTClient, I can connect to the host and port (it also uses a username and password) and it validates. I subscribe to a topic, but I don't receive any messages like I see in MQTT Explorer. Is there anything I should check that could be causing me to not receive the messages?

[Angus Robertson 645]

First place to look would be the Mosquitto log file, maybe subscribe failed for some reason.  

 

I did test the latest version against local and remote Mosquitto servers, but my knowledge of the MQTT protocol is almost nil so I don't know what to expect when I click the various test buttons.

 

Angus

 

[Mark- 32]

2 hours ago, Alberto Fornés said:

 I subscribe to a topic,...

Did you receive a SUBACK response when you subscribed?

 

[Angus Robertson 645]

My  Mosquitto log shows exactly that. 

 

2025-03-21T12:51:02: Received SUBSCRIBE from CID64860
2025-03-21T12:51:02:     update/memo (QoS 2)
2025-03-21T12:51:02: Sending SUBACK to CID64860

 

Angus

 

[Alberto Fornés 22]

This is the Mosquito log when connect to server:

 

Quote

1747327152: New connection from 192.168.1.130:52181 on port 1883.
1747327152: New client connected from 192.168.1.130:52181 as CID52177 (p1, c0, k10, u'keeptrack_cajas').
1747327152: Will message specified (19 bytes) (r0, q2).
1747327152:     will/CID52177
1747327152: Sending CONNACK to CID52177 (0, 0)
1747327152: Received SUBSCRIBE from CID52177
1747327152:     lectura/cajas/+ (QoS 1)
1747327152: CID52177 1 lectura/cajas/+
1747327152: Sending SUBACK to CID52177

 

[Alberto Fornés 22]

2 hours ago, Mark- said:

Did you receive a SUBACK response when you subscribed?

 

Yes, it appears as the last message when I log in and subscribe

[Mark- 32]

20 minutes ago, Alberto Fornés said:

Yes, it appears as the last message when I log in and subscribe

OK.

 

> but I don't receive any messages like I see in MQTT Explorer.

 

Is it the lack of a confirmation the subscribe was successful? or

Is the value in the server changing and you are not being notified?

[Alberto Fornés 22]

16 minutes ago, Mark- said:

OK.

 

> but I don't receive any messages like I see in MQTT Explorer.

 

Is it the lack of a confirmation the subscribe was successful? or

Is the value in the server changing and you are not being notified?

I don't receive any message in the event: MQTTClientMsg(Sender: TObject; aTopic: UTF8String; aMessage: AnsiString; aQos : TMQTTQOSType; aRetained : boolean)

[Angus Robertson 645]

The onClientMsg event is only triggered for published messages, 

 

Sorry, don't know off hand which event is triggered to acknowledge subscribe, you'll need to check the source code.

 

Angus

 

[Alberto Fornés 22]

Problem solved. I set the subscription to reading/boxes/+, and the correct option was reading/boxes/#. Thanks to those who responded and tried to help.👍