MQTT Connections
If an MQTT connection cannot be established or messages are not being received, check the following points. If the flow does not reach the transfer stage at all, first follow the steps in “” and “Transfer läuft nicht” .
Check the connection
The MQTT connection includes its own test: Open the plug-in configuration and trigger “Check connection”—see MQTT Plug-in Configuration .
The port and encryption do not match
The port depends on the encryption settings: When TLS/SSL is enabled, 8883 is typically set by default; without TLS/SSL, 1883 is generally used. Check both values together—see Connection Details and Enable TLS/SSL.
Also verify that the firewall allows traffic on the outbound port—see network-ports .
Multiple instances with the same client ID
If you are running multiple instances against the same broker, each one requires its own client ID. The field supports placeholders that generate a different ID for each instance, as well as a button for a random ID—see Authentication .
Cloud Profiles: Provider Symptom Tables
Each of the MQTT plug-in’s three cloud profiles includes its own symptom table with provider-specific messages—these lists the specific causes and solutions:
| Profile | Supported Symptoms | Page |
|---|---|---|
| Azure IoT Hub | 401 Unauthorized, Device not found, Connection refused (Port 8883), Access denied (Policy) | Azure |
| AWS IoT Core | Handshake/Authentication failed, Access denied, No route to host / Timeout, Duplicate Client-ID | AWS |
| Wago Cloud | Unable to establish connection, authentication failed, incorrect device addressed | Wago Cloud |
These tables apply to logging in to the respective cloud. They do not apply to a self-hosted broker; in that case, the connection test, port, encryption, and certificate verification remain the starting points.
Messages are received, but with a delay or in a different order
This is not a connection error. For information on how Quality of Service, connection persistence, and runtime affect performance, see MQTT Performance ; if Store and Forward is enabled, cached values are delivered in parallel with ongoing transfers and therefore do not necessarily arrive in their original order.