MqttHeartBeatClientHandler Class — netty Architecture

Source Code

example/src/main/java/io/netty/example/mqtt/heartBeat/MqttHeartBeatClientHandler.java lines 31–89

public class MqttHeartBeatClientHandler extends ChannelInboundHandlerAdapter {

    private static final String PROTOCOL_NAME_MQTT_3_1_1 = "MQTT";
    private static final int PROTOCOL_VERSION_MQTT_3_1_1 = 4;

    private final String clientId;
    private final String userName;
    private final byte[] password;

    public MqttHeartBeatClientHandler(String clientId, String userName, String password) {
        this.clientId = clientId;
        this.userName = userName;
        this.password = password.getBytes();
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        // discard all messages
        ReferenceCountUtil.release(msg);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        MqttFixedHeader connectFixedHeader =
                new MqttFixedHeader(MqttMessageType.CONNECT, false, MqttQoS.AT_MOST_ONCE, false, 0);
        MqttConnectVariableHeader connectVariableHeader =
                new MqttConnectVariableHeader(PROTOCOL_NAME_MQTT_3_1_1, PROTOCOL_VERSION_MQTT_3_1_1, true, true, false,
                                              0, false, false, 20, MqttProperties.NO_PROPERTIES);
        MqttConnectPayload connectPayload = new MqttConnectPayload(clientId,
                MqttProperties.NO_PROPERTIES,
                null,
                null,
                userName,
                password);
        MqttConnectMessage connectMessage =
                new MqttConnectMessage(connectFixedHeader, connectVariableHeader, connectPayload);
        ctx.writeAndFlush(connectMessage);
        System.out.println("Sent CONNECT");
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            MqttFixedHeader pingreqFixedHeader =
                    new MqttFixedHeader(MqttMessageType.PINGREQ, false, MqttQoS.AT_MOST_ONCE, false, 0);
            MqttMessage pingreqMessage = new MqttMessage(pingreqFixedHeader);
            ctx.writeAndFlush(pingreqMessage);
            System.out.println("Sent PINGREQ");
        } else {
            super.userEventTriggered(ctx, evt);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}