B4A Library MQTT - MQ Telemetry Transport for B4A

bluedude · Dec 30, 2014

Hi,

Have you done some experiments with putting this in a service in the background and keeping the connection open? What is the best approach to get the best results that messages always will be delivered? Trying to investigate if this can replace GCM.

Alberto Iglesias · Dec 30, 2014

Yes! It´s fantastic and independent way to do fast communication with others devices with a short messages, with this you have more control then GCM and the time can be much more faster, depends only the your server or MQTT rent service (like this for example: http://www.cloudmqtt.com/)

In a GCM we have problems with response time, can be late more than 30 minutes in some cases.

I do in a project inside a car company (imagine thousands/millions of simultaneous connections...) and we try before with GCM, but after we have a lot of success with MQTT way.

bluedude · Dec 31, 2014

Ok, just wondering with what settings on the server and client you are using it. I notice that it drops connections in a service and looses subscriptions. What QOS flags are you using on both sides? Would be nice if you can inform us a little more on the best settings to work with Android.

Till now I haven't been able to get a stable version with a service in the background.

Some questions:
- what QOS are you using on the server,
- are you using persistent on the server,
- do you use the stuff in an Android sticky service,
- how to keep topic subscriptions if connection has dropped.

Do you also have experience with Mosquito and the amount of users limit? Can it be run on a modest VPS with 5000-10000 users (connections).

Alberto Iglesias · Dec 31, 2014

Hello,

I used in some projects the MOSQUITTO server with more than 5000 devices....

If you need more then 1 million , I recommend use some server like IBM MESSAGESIGHT (http://www-03.ibm.com/software/products/en/messagesight)

or some cloud service dedicated to do this.

- The QoS we used in our projects depend of your message and propose of that, normally "2" but depends...
- Persistent on server, the same... depends of your type of service, if you can describe a little more, I can help you.
- Yes, I used in some android projects, receiving messages through the service, with no problem
- This is easily controlled by the events

If you need help for projects.. tell me.

Tks

adrianstanescu85 · Jan 10, 2015

Hello Alberto,

Is there any online reliable server other than the one at tcp://broker.mqtt-dashboard.com:1883 ? I'm asking this since this one tends to get stuck from time to time.

Thank you!
Adrian

Alberto Iglesias · Jan 10, 2015

This is better:
http://www.cloudmqtt.com/

You can create a free account, it´s hosted by AMAZON, is more powerful

adrianstanescu85 · Jan 10, 2015

Thank you for the tip, I just created an account and got my details for the Kitty plan!

They appear to use usernames and passwords, how can I integrate that into your sample app?

I have an URL that's like:

B4X:

mqtt://username:password@m20.cloudmqtt.com:portnumber

Maybe you can give an example based on that

adrianstanescu85 · Jan 10, 2015

Cause if I try to replace that URL as it is shown on my account, I get an error: "An error has occured in sub: java.lang.IllegalArgumentException on: mqtt://..."

imbault · Jan 10, 2015

Alberto Iglesias said:
This library was made based on MQTT Protocol

Installation instructions:
- Copy the .xml and .jar(s) files to your custom libraries folder
- Select in your REFERENCED LIBRARIES

Version history:
V1.0.0 (First public release - Donationware):
- Initial version

V1.0.2 (Release - Donationware):
- Implement method to get independence of threads

V1.0.4 (Release - Donationware):
- Implement method to subscribe a topic with QoS

V1.0.5 (Release - Donationware):
- Now can be used isConnected method "BEFORE" the first connection

MQTT
Author: Alberto Iglesias - alberto@visualnet.inf.br
Version: 1.01

MQTT
Events:

connectionlost ( As )

deliverycomplete (Token As String)

messageArrived (Topic As String, Message As String)

onConnect (Status as boolean As )

onDisconnect (Status as boolean As )

onInitialized ( As )

Fields:

CleanSession As Boolean

JavaDebug As Boolean

KeepAliveInterval As Int

QoS_AtLeastOnce As Int

QoS_AtMostOnce As Int

QoS_ExactlyOnce As Int

generatedClientId As String

Methods:

About As String

Connect (broker As String, ClientID As String, Username As String, Password As String) As Boolean

Disconnect As Boolean

Initialize (eventname As String)

Publish (Topic As String, Message As String, Qos As Int, Retained As Boolean)

Subscribe (Topic As String)

Unsubscribe (Topic As String)

Version As String

isConnected As Boolean

Permissions:

android.permission.ACCESS_WIFI_STATE

android.permission.INTERNET

How works the MQTT protocol

Communication Infrastructure

References:
http://mqtt.org/
http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html
Mosquitto Broker: http://mosquitto.org/

* This version is fully functional, the only one difference is when publishing a message the text "Donationware" is delivery with your message.
Please consider a simple €10 donation and I send to you the Library without "Donationware" text in a publish method.

Already available in B4J too: look in https://www.b4x.com/android/forum/threads/mqtt-mq-telemetry-transport-for-b4j.48184/

Hi @Alberto Iglesias ,
Maybe my question is stupid, I'm thinking of a domotic solution for my house
Is your project and this protocol can be used for domotic projects?

Do you know domotics sensors which use that protocols?

Thanks

Alberto Iglesias · Jan 10, 2015

Hello Andrian,

You need to use like this: Look my account in the same server

Dim strBroker As String = "tcp://m20.cloudmqtt.com:15968"
Dim strUsername As String = "myusername"
Dim strPassword As String = "mypassword"
Dim bRet As Boolean = objMqtt.Connect(strBroker,"",strUsername,strPassword)

Alberto Iglesias · Jan 10, 2015

Hey imbault,

Yes, this protocol is perfect for domotic projects, in this case use the Qos=2 (Quality of Service) for sure the signals arrival very well.

Best regards

adrianstanescu85 · Jan 10, 2015

Beautiful! Works perfectly! Thank you!

adrianstanescu85 · Jan 10, 2015

I have a quick question, it's actually not that important but it may help a lot...

I tried setting up a repeated message sending (and receiving) i.e. send a different text each 200ms. It seems that the "top speed" to achieve that is about 1 second though even if that 200ms timer ticks - the messages can't be sent faster. It's like the messages are queued and one has to wait for the previous one to be transmitted, which takes time. It doesn't seem to be a bandwidth issue since the messages are very very short, basically one or two characters long, so there's not a lot of info and even the free plan on CloudMQTT which is about 10kbps could handle that I guess.

I tried speeding this up with DoEvents when sending, but got no results. Is this a syncronization issue (so that an 'async' would work)?

Any ideas over this...?

Adrian

adrianstanescu85 · Jan 10, 2015

I just noticed that if I switch from QoS_ExactlyOnce to QoS_AtLeastOnce this works crazily well!!! Solved!!

Alberto Iglesias · Jan 11, 2015

Exactly!

and when choosing your server, it is one that can withstand many simultaneous connections.

In some projects in our company, we choose IBM MessageSight to be the broker.

Thanks

coslad · Jan 13, 2015

Hello Alberto

Is it possible to run a mqtt broker on a Android os?

Alberto Iglesias · Jan 13, 2015

Is perfectly possible!

With others libraries like HiveMQ you can, look this: https://github.com/hivemq

But why create a broker inside an android? what´s your idea?

coslad · Jan 14, 2015

Mqtt is a good choice in local net , but in a local net without internet is necessary to have a own broker.
The economics way is to install Mosquito on a raspberry pi board , but i don't like it because RB pi works in linux .
I prefer the "Banana Pi board" that is powerful than Raspberry and it work on Android .
And i can even use a smartphone (in a local net ) as broker

Alberto Iglesias · Jan 14, 2015

In one of ours projects, in the moment when the device is offline, we have a sqllite to save the messages and then when the device is online again, the messages are being emptied by the broker

coslad · Jan 14, 2015

Alberto, are you answering to me? I didn't understand

Is the broker that saves the message and sends it to the device when it is online ? So like a chat message application !

B4A Library MQTT - MQ Telemetry Transport for B4A

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