mqtt5 0.2.0

A pure-Dart MQTT 5.0 client library with QoS 0/1/2, session resume, flow control and enhanced authentication.

0.2.0

Bug fixes, almost all of them in the connection lifecycle rather than the protocol engine. If you are on 0.1.0 it is worth upgrading: several of these could hang or crash a long-running app. Everything below has a test.

The worst one first. A malformed packet from the broker (PUBLISH with DUP set on QoS 0, a reserved QoS value, a reserved Retain Handling value) came out of the decoder as an ArgumentError or RangeError, and the inbound handler only caught MqttException, so it escaped and took the enclosing zone with it. One bad packet from a broken or hostile broker was enough to kill the app. Decoding now produces MqttMalformedPacketException, and anything thrown while decoding or dispatching is treated as a protocol error: the client sends a DISCONNECT with the matching reason code, closes the connection and reconnects.

Two ways the client could get stuck:

• A CONNACK rejection left the connect loop still marked as running and never released the socket, so the transport leaked and every later connect() quietly did nothing.
• disconnect() never failed the futures that were waiting on an acknowledgement, so in-flight QoS 1/2 publishes and pending subscribe/unsubscribe calls waited forever. They now fail with MqttConnectionException, and there is a real timeout on top of that (see below).

Fatal errors on a reconnect had nowhere to go, since the reconnect paths start the connect loop without a caller. They escaped as unhandled asynchronous errors and the client died silently. There is now an MqttClient.errors stream for them.

Other fixes:

• disconnect() before connect() threw LateInitializationError.
• Server capabilities (Maximum QoS, Retain Available, Topic Alias Maximum and friends) leaked from one connection into the next. They are reset per CONNACK now, so a property the new broker did not send falls back to the spec default instead of keeping the old value.
• An exception thrown by a messages listener unwound into the socket event handler and got reported as a protocol error. The stream is no longer synchronous.
• Packet identifiers were released twice, once by the acknowledgement handler and once by the publish call. In the wrong interleaving that frees an identifier already handed out to another message.
• A Topic Alias was recorded before the PUBLISH carrying the full topic name had been written. If that write failed, every later publish to the topic referenced an alias the broker had never seen. It is recorded after a successful write now.
• Transport teardown was not awaited before the connect loop restarted, so a new transport could be thrown away by the previous teardown.
• A DISCONNECT from the broker was only logged. The connection is closed now, and reason codes like Server Moved or Banned stop the client rather than looping on reconnect.
• subscribeAll threw away the filters a broker accepted whenever it rejected any other filter in the same SUBACK. The accepted ones are kept, and will be re-established after a session loss. SUBACK and UNSUBACK reason code counts are checked against the number of filters sent.
• The Assigned Client Identifier from CONNACK was ignored. It is used for reconnects now and readable as MqttClient.effectiveClientId.
• Maximum Packet Size checks on inbound packets left out the fixed header.
• A keepAlive over 65535 seconds produced a confusing error from deep inside the packet encoder.

New:

• autoReconnect (default true). There was previously no way to turn reconnection off. With false, connect() fails on the first unsuccessful attempt and a dropped connection is not retried.
• MqttClient.errors and MqttClient.close(), the latter releasing the message, state and error streams.
• MqttClient.effectiveClientId.
• The authenticating and disconnecting connection states are actually emitted now, having been declared but never used.

Breaking changes:

• publish, subscribe and unsubscribe give up after operationTimeout (30 seconds by default) and throw MqttTimeoutException. Pass Duration.zero to wait forever like 0.1.0 did.
• The barrel library no longer exports internals: ConnectionManager, FlowController, KeepAliveManager, PacketIdentifierPool, MqttSession and the session stores. MemoryTransport moved to package:mqtt5/testing.dart.
• MqttQos.fromValue and MqttSubscriptionOptions.fromByte throw MqttMalformedPacketException rather than ArgumentError/RangeError.
• publish rejects wildcards and empty topic names locally instead of letting the broker close the connection over it.
• Dropped the placeholder bin/mqtt5.dart.

0.1.0

• Initial release: MQTT 5.0 client with QoS 0/1/2, session resume, Receive Maximum flow control, Topic Alias, enhanced authentication, keep alive, automatic reconnect, TLS, and runtime metrics.