mqtt | 易学教程

Does AWS-IOT Mqtt Broker remember subscribed clients and undelivered messages across client Connections?

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问题 AWS Documentation here ( [http://docs.aws.amazon.com/iot/latest/developerguide/iot-message-broker.html] ) says this :- "The message broker maintains a list of all client sessions and the subscriptions for each session. When a message is published on a topic, the broker checks for sessions with subscriptions that map to the topic. The broker then forwards the publish message to all sessions that have a currently connected client. For all matching sessions that do not have a connected client,

How to implement MQTT in this particular usecase of Android?

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问题 My usecase: A user logged into my app, should be able to send messages to himself logged into the app on another Android device. If the user has more than one devices, then once he opens the message, the notification on other devices must disappear. Doubts: How to send data to a particular user across devices? I understand how to send messages to different users on different devices using GCM but this seems rather confusing. How to achieve this in MQTT with adequate security? I read as much

Thread issue while subscribing to MQTT in Python using Paho MQTT

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问题 I have a python program which listens to an MQTT topic and needs to process the message. I specify a number of arguments from the command line to evaluate the message differently. import argparse import datetime import json import paho.mqtt.client as mqtt ### MQTT Functions def on_connect(mqttc, obj, flags, rc): print("Connected! - " + str(rc)) def on_message(mqttc, obj, msg): print(msg.topic+" "+str(msg.qos)+" "+str(msg.payload)) def on_publish(mqttc, obj, mid): print("Published! "+str(mid))

ESP32 应用实践：基于混杂接收模式的人流量检测

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前言 ESP32 是一颗低功耗、高集成度、性能稳定的 Wi-Fi /BLE 芯片，是物联网开发的首选设备。它采用 2.4 GHz Wi-Fi 加蓝牙双模芯片，采用 TSMC 低功耗 40nm 技术，功耗性能和射频性能最佳，安全可靠，易于扩展至各种应用。同时集成了双核 160 MHz MCU、两个浮点运算单元 (FPU)、硬件安全加速器、电容触摸传感器、霍尔传感器、ADC、DAC、蓝牙/Wi-Fi 协议栈、TR 滤波器、双工器、功率放大器、接收低噪声放大器、射频 balun 和天线开关。ESP32 的外围器件不超过 10 个，即可实现强大的处理性能、可靠的安全性能，以及 Wi-Fi 和蓝牙功能。可作为独立系统运行应用程序或是主机 MCU 的从设备，通过 SPI / SDIO 或 I2C / UART 接口提供 Wi-Fi 和蓝牙功能。专为移动设备、可穿戴电子产品和物联网应用而设计。该款芯片拥有业内最高水平的低功耗芯片的所有特征，比如精细分辨时钟门控、省电模式和动态电压调整等。集成了更多的元器件，性能稳定，易于制造，工作温度范围达到 -40°C 到 +125°C。ESP32 还集成了先进的自校准电路，实现了动态自动调整，可以消除外部电路的缺陷以及适应外部条件的变化。总之，是一款极其优秀的物联网芯片。混杂模式也称 sniffer, 也称嗅探模式。就是接收所有经过网卡的数据包

Android - Paho Mqtt client does not receive messages once network connectivity changes (mobile data disabled and enabled again)

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问题 I am using Mosquitto Mqtt along with paho API to receive push messages on android device. But as soon as the network connectivity changes it stops receiving messages. Here are the steps to reproduce the issue with simple test case: 1) Create a simple activity. 2) On Activity StartUp connects to mosquitto test server (test.mosquitto.org:1883) through paho API. 3) Subscribe to some topic. 4) Publish some message to the topic. Result: Mqtt Client receives all the messages published to the topic.

MQTT-SN on Raspberry pi3 , 6lowpan over BLE

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I'm trying to set a MQTT-SN broker (rsmb) ,and using several pi3 as clients. First , I will build a 6lowpan over ble connection. Setting pi3 (RASPBIAN JESSIE kernel v4.4) sudo su hciconfig hci0 reset modprobe bluetooth_6lowpan echo 1 > /sys/kernel/debug/bluetooth/6lowpan_enable hciconfig hci0 leadv BLE gateway (Ubuntu 14.04) sudo su hciconfig hci0 reset modprobe bluetooth_6lowpan echo 35 > /sys/kernel/debug/bluetooth/6lowpan_psm echo 1 > /proc/sys/net/ipv6/conf/all/forwarding echo "connect *my_pi3_bluetooth_address* 1" > /sys/kernel/debug/bluetooth/6lowpan_control ifconfig bt0 add 2001:xxxx

Connecting Unity3d Android application to ActiveMQ broker using MQTT

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问题 I am trying to connect an Unity3d Android application to an ActiveMQ server using MQTT protocol. In the log attached below I can see that the server is refusing me the connection. I have correctly portforwarded the required port to be accessible from outside. I have also tried to connect from the local network using the device's wi-fi. I am using a MQTT library for unity which can be found here: https://m2mqtt4unity.codeplex.com/ Currently the same application, the example that can be found

How to connect to my MQTT Broker in Openshift

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Following these two tutorials ( https://www.anavi.org/article/182/ and http://wei-meilin.blogspot.tw/2014/05/red-hat-openshift-xpaas-simple-mqtt.html ) I have installed a MQTT Broker using JBoss Fuse. Although my mqtt-container disappears after a while (I don't know why) I can make a port-forwarding and test the broker. But I would like to know how to connect directly to the broker. Do you know how to do it? I have tried this tutorial ( http://training.runcloudrun.com/advanced/16-Network-and-Protocols.md.html - AMQ Example) but I don't have access to "/var/lib/openshift/.httpd.d/sniproxy.cfg"

How to work with MQTT in Wildfly

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I am working on a platform to monitor and control devices which use MQTT for the communication layer. I use REST endpoints for the Angular2 based SPA Web. The backend is developed in JEE using WildFly which support out of the box the MQTT protocol through is JMS Broker(Active MQ). I am new in JEE and don’t know a lot of things: - I have never used the JMS System - I can’t find any information o tutorial to point me in the right way to get MQTT messages through a JMS Application. Can you help me to build a very basic App on WildWfly which demonstrates how to consume/produce JMS Messages through

Google iot core connection status

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I am using Google IOT core with mongoose os. I wanted to update device connection status to firestore. But i am unable to find event which reports mqtt connection status to pub/sub like when device disconnects or reconnect i.e if device is offline or not. I am stuck on this problem for days.Any help will be appreciated Update As @devunwired mentioned in this response it is now possible to monitor Stackdriver logs for disconnect events. You must have at a minimum enabled INFO level logging on your project in IoT Core > Registries > [your registry] > Edit Registry > Select "Info" log level >