README.md

MQTT-SN Java Client

Full, dependency free java implementation of the MQTT-SN protocol specification for a client. Uses the mqtt-sn-codecs for wire transport and comes equip with UDP network transport by default. NOTE: As with all the modules in this project, the persistence, transport and wire traffic layer is entirely pluggable.

Quick start

Configure your details using the code below and run Example.

public class Example {
    public static void main(String[] args) throws Exception {

        MqttsnFilesystemStorageService filesystemStorageService =
                new MqttsnFilesystemStorageService();

        //-- use the client transport options, which will use random unallocated local ports
        MqttsnUdpOptions udpOptions = new MqttsnClientUdpOptions();

        //-- runtimes options can be used to tune the behaviour of the client
        MqttsnOptions options = new MqttsnOptions().
                //-- specify the address of any static gateway nominating a context id for it
                        withNetworkAddressEntry("gatewayId", NetworkAddress.localhost(MqttsnUdpOptions.DEFAULT_LOCAL_PORT)).
                //-- configure your clientId
                        withContextId("clientId1").
                //-- specify and predefined topic Ids that the gateway will know about
                        withPredefinedTopic("my/predefined/example/topic/1", 1);

        //-- using a default configuration for the controllers will just work out of the box, alternatively
        //-- you can supply your own implementations to change underlying storage or business logic as is required
        AbstractMqttsnRuntimeRegistry registry = MqttsnClientRuntimeRegistry.defaultConfiguration(filesystemStorageService, options).
                withTransport(new MqttsnUdpTransport(udpOptions)).
                //-- select the codec you wish to use, support for SN 1.2 is standard or you can nominate your own
                        withCodec(MqttsnCodecs.MQTTSN_CODEC_VERSION_1_2);

        AtomicInteger receiveCounter = new AtomicInteger();
        CountDownLatch latch = new CountDownLatch(1);

        //-- the client is Closeable and so use a try with resource
        try (MqttsnClient client = new MqttsnClient()) {

            //-- the client needs to be started using the configuration you constructed above
            client.start(registry);

            //-- register any publish receive listeners you require
            client.registerPublishReceivedListener((IClientIdentifierContext context, TopicPath topic, int qos, boolean retained, byte[] data, IMqttsnMessage message) -> {
                receiveCounter.incrementAndGet();
                System.err.println(String.format("received message [%s] [%s]",
                        receiveCounter.get(), new String(data, MqttsnConstants.CHARSET)));
                latch.countDown();
            });

            //-- register any publish sent listeners you require
            client.registerPublishSentListener((IClientIdentifierContext context, TopicPath topic, int qos, boolean retained, byte[] data, IMqttsnMessage message) -> {
                System.err.println(String.format("sent message [%s]",
                        new String(data, MqttsnConstants.CHARSET)));
            });



            //-- issue a connect command - the method will block until completion
            client.connect(360, true);

            //-- issue a subscribe command - the method will block until completion
            client.subscribe("my/example/topic/1", 2);

            //-- issue a publish command - the method will queue the message for sending and return immediately
            client.publish("my/example/topic/1", 1,  false, "hello world".getBytes());

            //-- wait for the sent message to be looped back before closing
            latch.await(30, TimeUnit.SECONDS);

            //-- issue a disconnect command - the method will block until completion
            client.disconnect();
        }
    }
}