I am trying to connect HiveMQ Edge via MQTT bridge to Azure Event Grid. For that purpose I created self signed certificates. After filling in the details on host username and certificate in the MQTT bridge UI, I get the following message:
Bridge az disconnected: CONNECT failed as CONNACK contained an Error Code: IMPLEMENTATION_SPECIFIC_ERROR.
Azure side is set up correctly correctly, with regards to certificates, clients, permission bindings. This was verified by using MQTTX client with same certificates.
I would like to provide you with a technical explanation of the current situation.
HiveMQ Edge is designed to include a User Property “client-agent=HiveMQ-Edge; 2025.14” in its MQTT5 CONNECT messages as part of its standard protocol implementation. However, Azure Event Grid’s MQTT5 support has certain limitations that affect this functionality.
According to Microsoft’s documentation (MQTT Features Supported by Azure Event Grid MQTT Broker - Azure Event Grid ), Azure Event Grid does not support user properties on CONNECT, SUBSCRIBE, DISCONNECT, PUBACK, and AUTH packets. The service documentation specifically states that if any of these requests include user properties, the request will fail.
This limitation creates an incompatibility between HiveMQ Edge Bridge and Azure Event Grid’s MQTT5 implementation, as the required user property in the CONNECT message causes connection failures.
Unfortunately, there is no available workaround for this issue at present, as it stems from fundamental differences in protocol support between the two services.
Should you wish to add any new functionality in future versions of HiveMQ Edge, I would encourage you to submit a feature request through https://github.com/hivemq/hivemq-edge/issues
