Troubleshoot

CONNACK 0x95 “Packet too large”

Broker rejects the packet size.

Reduce payload size or set max_packet_size in the MQTT 5 CONNECT properties.

No incoming PINGRESP

Application traffic is more frequent than the keep-alive interval.

This is expected — the broker resets the timer whenever data flows.

Retained message not cleared

Message published without clearing retain flag.

Republish the same topic with an empty payload and --mqtt_pub_retain.

TLS handshake fails

CA bundle missing or host-name mismatch.

Verify --ssl_ca_file or (for tests) add --ssl_allow_untrusted.

Session resume not working

--mqtt_clean_start flag still set.

Omit --mqtt_clean_start and set a non-zero --mqtt_session_expiry_interval.