mqtt

I'm surely missing something about how the whole MQTT protocol works, as I can't grasp the usage pattern of Last Will Testament messages: what's their purpose? One example I often see is about informing that a device has gone offline. It doesn't make very much sense to me, since it's obvious that if a device isn't publishing any data it may be offline or there could be some network problems. So, what are some practical usages of the LWT? What was it invented for? LWT messages are not really concerned about detecting whether a client has gone offline or not (that task is handled by keepAlive

I use QTimer to send periodically 'Ping' packet to the server (MQTT client). But it timer is not absolutely accurate. After some time of working it has some delay and server broken connection. I try to use different Qt::TimerType, but it does not help. I need the most accurate timer. Do you have any ideas? Thank you! EDIT (Frederik solution) I have done something this: tthread.h class TThread : public QThread { Q_OBJECT void run(); public: explicit TThread(QObject *parent = 0); signals: private slots: void timerOut(); }; tthread.cpp TThread::TThread(QObject *parent) : QThread(parent) { } void

When I try the below code to connect to the mosquitto broker, as you know, connecting to the broker might takes few seconds/minutes, and during that time when the button pressed to connect, it remains pressed till the connection established and when the connection established the button released back to its normal state. As far as I know, there are two way for connecting a client using paho java API , the blocking method and unblocking method . my question is, how to use the unblocking method ? beow is my attempt to use the blocking method Code_1 : //mqttFactory public final class

本文主要介绍，MQTT 基本概念和实现方式： 1.概述 1.1MQTT协议 MQTT（Message Queuing Telemetry Transport，消息队列遥测传输协议），由IBM在1999年发布，是一种基于发布/订阅（Publish/Subscribe）模式的轻量级通讯协议，该协议构建于TCP/IP协议上，属于应用层协议，只要是支持TCP/IP协议栈的地方，都可以使用MQTT。 MQTT最大的优点在于可以以极少的代码和有限的带宽，为远程设备提供实时可靠的消息服务。作为一种低开销、低带宽占用的即时通讯协议，MQTT在物联网、小型设备、移动应用等方面有广泛的应用。 MQTT 协议中文文档链接： https://mcxiaoke.gitbooks.io/mqtt-cn/content/mqtt/01-Introduction.html 1.2发布-订阅模式 在“发布者-订阅者”模式中，称为发布者的消息发送者不会将消息编程为直接发送给称为订阅者的特定接收者。这意味着发布者和订阅者不知道彼此的存在。 存在第三个组件 ，称为 代理或消息代理或事件总线 ，它 由发布者和订阅者都知道 ，它 过滤所有传入的消息并相应地分发它们 。换句话说，pub-sub是用于在不同系统组件之间传递消息的模式，而这些组件不知道关于彼此身份的任何信息。经纪人如何过滤所有消息？实际上，有几个消息过滤过程

Following this , I have this code @Bean open fun messageConverter(om: ObjectMapper): MessageConverter { return Jackson2JsonMessageConverter(om) } @Bean open fun rabbitListenerContainerFactory(cf: ConnectionFactory, mc: MessageConverter ): SimpleRabbitListenerContainerFactory { val factory = SimpleRabbitListenerContainerFactory() factory.setConnectionFactory(cf) factory.setMessageConverter(mc) return factory } @Bean open fun builder(): Jackson2ObjectMapperBuilderCustomizer { return Jackson2ObjectMapperBuilderCustomizer { it.modules(JavaTimeModule(), KotlinModule()) it.featuresToDisable

XMPP协议、MQTT协议、HTTP协议、CoAP协议的基本比较 时间 2016-05-19 07:11:57 IT社区推荐资讯 原文 http://itindex.net/detail/55605-xmpp-mqtt-http 主题 XMPP MQTT HTTP 一、先看下相关国外的专业数据对四大协议的比较： Protocol CoAP XMPP RESTful HTTP MQTT Transport UDP TCP TCP TCP Messaging Request/Response Publish/Subscribe Request/Response Request/Response Publish/Subscribe Request/Response 2G, 3G, 4G Suitability (1000s nodes) Excellent Excellent Excellent Excellent LLN Suitability (1000s nodes) Excellent Fair Fair Fair Compute Resources 10Ks RAM/Flash 10Ks RAM/Flash 10Ks RAM/Flash 10Ks RAM/Flash Success Storied Utility Field Area Networks Remote

I am having two tomcat servers running same web application. Both the web applications subscribe to topic 1 in MQTT server. Whenever message is received in topic 1 both the applications receive the message. But I want only one server to process the request instead of both. The worst case I have to do condition check at both the web applications to allow one time processing. Any suggestions for this case ? You need to use a MQTT broker that supports Shared Subscriptions 1 This feature allows you to have multiple clients subscribed to the same topic and the broker will deliver them in a round

I'm using Arduino Uno and Wi-Fi shield. I'm trying to implement MQTT protocol for communication and I tried two libraries for Arduino. First one is Knolleary's PubSubClient: http://pubsubclient.knolleary.net/ . I modified original example a little bit to use WiFi module instead of ethernet. Sending works but not every time (sometimes, the message is sent and sometimes not). But receiving via callback function doesn't work at all. Here is my code: /* Basic MQTT example with Authentication - connects to an MQTT server, providing username and password - publishes "hello world" to the desired