mqtt | 易学教程

mqtt mosquitto bridge horizontal scaling

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问题 I have one load balancer i.e aws elb all the pub/sub will be coming via that elb two mosquitto broker A & mosquitto broker B under elb one mosquitto broker to sync topic between this two brokers(mosquitto.broker.sync) TRY ONE this is how the configuration for mosquitto broker which sync topics between node A and B looks alike mosquitto.broker.sync: ## connection mosquitto-bridge try_private false address mosquitto.broker.A:1883 mosquitto.broker.B:1883 start_type automatic round_robin true

SparkStreaming, RabbitMQ and MQTT in python using pika

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问题 Just to make things tricky, I'd like to consume messages from the rabbitMQ queue. Now I know there is a plugin for MQTT on rabbit (https://www.rabbitmq.com/mqtt.html). However I cannot seem to make an example work where Spark consumes a message that has been produced from pika. For example I am using the simple wordcount.py program here (https://spark.apache.org/docs/1.2.0/streaming-programming-guide.html) to see if I can I see a message producer in the following way: import sys import pika

Get a list of connected client IDs from MQTT client

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问题 As a mqtt client connected to mosquitto is it possible to retrieve a list of client IDs who are also connected to the broker? 回答1: method I: handle in client logic as @user1048839 says, use client's LWT & online publish msg, maintain client status on a custom topic. subscript this topic & maintain client list self. if pub retain msg, once sub will get the client list. method II: change mosquitto broker code official code not support online_list, so I patched mosquitto 1.5.4, add 2 custom sys

Is message order preserved in MQTT messages?

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问题 I wonder if the message sent order is preserved. That is, when a publisher sends a sequence of messages, is each subscriber guaranteed to receive the same sequence as the publisher had sent it? For both clean and persistent sessions? 回答1: A summary of the message ordering capabilities in MQTT 3.1.1 can be found in the specification itself here. In summary: no guarantees are made about the relative ordering of messages published with different QoS values. (for example, QoS 0 can over take QoS

KEPServerEX物联网网关（IoT Gateway）REST客户端代理（非原创）

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（中文版）资料来源于【OPC-KEPServerEX学习KEPWare交流】905485143群的【455196383】【零下一度】一。 KEPServerEX 物联网网关 REST 客户端代理演示在KSE中，首先构建一个带有通道/设备/标签的模拟器系统。例如，下面是三个随机项目。直接到IoT网关插件，添加新代理。从类型列表中选择REST Client。终结点设置：将默认端口3000更改为1880（与RED使用的端口一致），然后使用'/keptest'（后面是节点RED中的URL）。将此处演示的发布速率从10000毫秒更改为1000毫秒。单击“下一步”直到完成将三个现有的随机标签添加到REST客户端代理中。在Node RED中，生成如下所示的流。 <Method:POST；URL:/keptest> 一旦部署配置，JSON格式的数据就会出现在“调试”控制台中从调试控制台中，我们可以发现，每秒钟都有一个JSON格式的上下文显示所有三个随机标记的值、质量和时间戳。 2 。KEPServerEX 物联网网关MQTT 客户端代理演示添加MQTT客户端代理设置代理如下（在此演示中将发布速率更改为1000毫秒）单击Next直到Finish，然后将三个随机标记添加到MQTT客户机代理中 MQTT协议定义了MQTT代理的请求

MQTT 主题的高级特性

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 什么是主题 MQTT 协议通过网络传输应用消息。应用消息通过 MQTT 传输时，它们有关联的服务质量（QoS）和主题（Topic）。主题本质上是一个字符串，MQTT 协议规定主题是UTF-8编码的字符串，这意味着，主题过滤器和主题名的比较可以通过比较编码后的 UTF-8 字节或解码后的 Unicode 字符。主题名和主题过滤器主题名附加在应用消息上的一个标签，服务端已知且与订阅匹配。服务端发送应用消息的一个副本给每一个匹配的客户端订阅。主题过滤器订阅中包含的一个表达式，用于表示相关的一个或多个主题。主题过滤器可以使用通配符。主题可能是管理员在服务端预先定义好的，也可能是服务端收到第一个订阅或使用那个主题名的应用消息时动态添加的。服务端也可以使用一个安全组件有选择地授权客户端使用某个主题资源。如果订阅的主题过滤器与消息的主题名匹配，应用消息会被发送给每一个匹配的客户端订阅。主题资源可以是管理员在服务端预先定义好的，也可以是服务端收到第一个订阅或使用那个主题名的应用消息时动态添加的。服务端可以使用一个安全组件有选择地授权客户端使用某个主题资源。主题和主题过滤器命名的规则所有的主题名和主题过滤器必须至少包含一个字符。主题名和主题过滤器是大小写敏感的。 ACCOUNTS 和 Accounts

Mqtt How a client can get to know that another client is connected or not

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问题 Hello guys my problem is that I need to keep device(clients) status as they are online or not. I am connecting through a client id and from subscribing there will topic I can get to know that device is disconnected but if they connect again how can I check they connect again. 回答1: The short answer is you don't (at a protocol level). Publishers and subscribers are totally unaware of each other, messages are sent to topics not to specific subscribing clients. The slightly longer version: You

Android Studio - MQTT not connecting

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问题 I have just started learning using MQTT protocol with Android Studio. Using mosquitto broker, I am able to exchange messages between pub/sub windows. But when I send message to broker through android studio, the app builds successfully but nothing displays on broker's end & system prints Connection Failure. The same code works fine on eclipse java application, but not working on android although required libraries and dependencies have been added. Please help, what am I missing in this basic

MQTT broker for Android

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问题 Does anyone know of an MQTT broker that runs on an Android smartphone? I tried to Google and found nothing, and on the app store there seems to be only one app with just 10 downloads, so I'm not sure how well it works. 回答1: Add these dependencies to the gradle dependencies{ compile 'io.moquette:moquette-netty-parser:0.8.1' compile 'io.moquette:moquette-broker:0.8.1' compile 'io.moquette:moquette-parser-commons:0.8.1' } And use io.moquette.server.Server server = new io.moquette.server.Server()

How to test the `Mosquitto` server?

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问题 I am new to Mosquitto and MQTT , I downloaded the Mosquitto server library but I do not know how to test it. Is there any way to test the Mosquitto server? 回答1: In separate terminal windows do the following: Start the broker: mosquitto Start the command line subscriber: mosquitto_sub -v -t 'test/topic' Publish test message with the command line publisher: mosquitto_pub -t 'test/topic' -m 'helloWorld' As well as seeing both the subscriber and publisher connection messages in the broker