ca_file or the system's CAs (MOSQ_OPT_TLS_USE_OS_CERTS), client
certificate, broker certificate and host name verified, settings errors
reported before connecting. The client thread blocks SIGPIPE: with TLS,
a write to a connection the broker closed killed the process. The
reason of a failed handshake (libmosquitto's log) is appended to the
error. tst_mqtt covers TLS with test certificates in tests/data (D44).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
MqttClient is the interface the HA layer will use; MosquittoClient
implements it with one std::thread for DNS, connect, network loop and
reconnect with backoff (D45, amends D42: mosquitto_loop_start() blocks
the caller on DNS and stops silently on TLS/protocol errors).
tst_mqtt tests it against a local mosquitto: messages, retained
messages, first connect and reconnect, last will, login.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
matzmanandClaude Opus 5.5