Implemented MQTT QoS 1

src/zutil/net/mqtt/MqttBroker.java

@@ -464,8 +464,6 @@ public class MqttBroker extends ThreadedTCPNetworkServer {
         }
 
         protected void handlePacket(MqttPacketHeader packet) throws IOException {
-            // TODO: QOS 1
-            // TODO: QOS 2
             // TODO: handle connection timeout
 
             switch (packet.type) {
@@ -502,11 +500,25 @@ public class MqttBroker extends ThreadedTCPNetworkServer {
         }
 
 
-        private void handlePublish(MqttPacketPublish publishPacket) {
+        private void handlePublish(MqttPacketPublish publishPacket) throws IOException {
-            if (publishPacket.getFlagQoS() != 0)
+            // TODO: QOS 2
-                throw new UnsupportedOperationException("QoS larger then 0 not supported (value: " + publishPacket.getFlagQoS() + ").");
+
+            if (publishPacket.getFlagQoS() == 2)
+                throw new UnsupportedOperationException("QoS value of 2 not supported.");
             if (publishPacket.getFlagQoS() >= 3)
-                throw new IllegalArgumentException("QoS value of 3 is not valid.");
+                throw new IllegalArgumentException("QoS value of 3 or larger is not valid value (received QoS: " + publishPacket.getFlagQoS() + ").");
+
+            // QoS=0, the Receiver:
+            //   - Accepts ownership of the message when it receives the PUBLISH packet.
+
+            // QoS=1, the Receiver
+            //   - MUST respond with a PUBACK Packet containing the Packet Identifier from the incoming PUBLISH Packet, having accepted ownership of the Application Message
+            //   - After it has sent a PUBACK Packet the Receiver MUST treat any incoming PUBLISH packet that contains the same Packet Identifier as being a new publication, irrespective of the setting of its DUP flag.
+            if (publishPacket.getFlagQoS() == 1) {
+                MqttPacketPublishAck publishAckPacket = new MqttPacketPublishAck();
+                publishAckPacket.packetId = publishPacket.packetId;
+                sendPacket(publishAckPacket);
+            }
 
             logger.finer("[" + clientId + "] Publishing to topic: " + publishPacket.topicName);
             broker.publish(publishPacket.topicName, publishPacket.payload);
@@ -549,6 +561,12 @@ public class MqttBroker extends ThreadedTCPNetworkServer {
         }
 
 
+        /**
+         * Handle data that has been published to the clients subscriptions
+         *
+         * @param topic the name of the topic
+         * @param data  the published data
+         */
         @Override
         public void dataPublished(String topic, byte[] data) {
             try {
@@ -559,13 +577,17 @@ public class MqttBroker extends ThreadedTCPNetworkServer {
                 publishPacket.payload = data;
                 sendPacket(publishPacket);
 
-                // TODO: QOS 1
                 // TODO: QOS 2
             } catch (IOException e) {
                 logger.log(Level.WARNING, "Was unable to publish topic to client " + clientId, e);
             }
         }
 
+        /**
+         * Will publish this clients will packet.
+         *
+         * @throws IOException
+         */
         private void sendWillPacket() throws IOException {
             if (willPacket != null) {
                 logger.fine("[" + clientId + "] Publishing will packet.");

test/zutil/net/mqtt/MqttBrokerTest.java

@@ -1,7 +1,7 @@
 /*
  * The MIT License (MIT)
  *
- * Copyright (c) 2020 Ziver Koc
+ * Copyright (c) 2020-2025 Ziver Koc
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -388,6 +388,32 @@ public class MqttBrokerTest {
         assertEquals( null, subscriber2.receivedPayload);
     }
 
+    @Test
+    public void publishQoS1() throws IOException {
+        // Setup broker
+        MqttBroker broker = new MqttBroker();
+        MqttConnectionThreadMock thread = new MqttConnectionThreadMock(broker);
+        MqttSubscriptionListenerMock subscriber = new MqttSubscriptionListenerMock();
+        broker.subscribe("test/topic", subscriber);
+
+        // Setup publish
+        MqttPacketPublish publish = new MqttPacketPublish();
+        publish.topicName = "test/topic";
+        publish.setFlagQoS(1);
+        publish.packetId = 33;
+        publish.payload = new byte[]{42};
+
+        thread.handlePacket(publish);
+
+        // Check response
+        assertEquals(1, thread.sentPackets.size());
+        MqttPacketPublishAck ackPacket = (MqttPacketPublishAck) thread.sentPackets.get(0);
+        assertEquals(33, ackPacket.packetId);
+
+        assertEquals("test/topic", subscriber.receivedTopic);
+        assertEquals((byte) 42, subscriber.receivedPayload[0]);
+    }
+
     @Test
     public void publishBadQos() throws IOException {
         // Setup broker