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MQTT Problems

Troubleshoot MQTT broker connectivity and publishing issues.

Cannot Connect to Broker

Check Broker Status

  1. Verify broker is running
  2. Check broker logs
  3. Test with MQTT client: 
    mosquitto_sub -h <broker> -p 1883 -t '#' -v

Authentication Failures

Symptoms: - "Authentication failed" in logs - Connection rejected

Solutions: - Verify username/password - Check user permissions on broker - Ensure user can publish to topics

TLS/SSL Issues

Symptoms: - TLS handshake failure - Certificate errors

Solutions: - Verify certificates are valid - Check certificate paths - Ensure TLS versions match - Verify CA certificate

Publishing Issues

Data Not Appearing

Check: 1. MQTT broker connected (green status) 2. Device is polling 3. Subscribe to correct topics: 

spBv1.0/<group_id>/DDATA/<node_id>/#

Message Rate Too High

Symptoms: - Broker overload - Slow publishing

Solutions: - Enable RBE on slowly-changing tags - Increase poll rates for non-critical data - Use burst polling instead of continuous

Broker Disconnects Frequently

Possible Causes: - Keep-alive too short - Network instability - Broker resource limits - Firewall killing connections

Solutions: - Increase keep-alive interval - Check network quality - Review broker capacity - Configure broker redundancy

Sparkplug Issues

SCADA Not Seeing Device

Check: 1. SCADA subscribed to correct topics 2. DBIRTH published (device birth) 3. Sparkplug group ID correct 4. Edge node ID correct

DCMD Commands Not Working

Check: 1. Tag configured as writable 2. Tag uses Holding Register (HR) 3. Correct metric name in DCMD 4. Check command logs

Next Steps