B4J Question [MQTT] MQTT and Limits -> Creating an MQTT Extender

As I am working (is too difficult as i see and not easy to make it in some hours) on this "Tutorial"... sharing thoughts..

the question: Where an MQTT synchronous mode can be used ?

What "I" mean with synchronous may be not the same with what is possible exists (something read about paho c client library, etc)... or may be is the same...

Let's have a Real Life Example...

First... let's say we have two clients (at a broker/mqtt server)...
One that will share Data of his DB when asked for (Client-A) and other (Client-B) that will ask/request for specific data from Client-A...

How works in when in asynchronous mode...

Client-A opens DB... and wait for messagearrive (the request from Client-B)
when see the request will send the data
* simple and clean...

but in real life - how the Client-B will get the data asked...
1) What if those data-resulset are so many (200MB) that will make all freeze or if mqtt broker not has the feature of so big messages -will not transfer...?
2) and if the data-resultset is ok to transfer... when will come to Client-B.. ? --need to check with --messagearrived-- (answer - but not this we want - right ?)

How will be working in synchronous mode or at the mode we will create... ?

Client-A opens DB... and wait for messagearrive (the request from Client-B)
when see the request will send the data
* simple and clean...

Client-B, Request for Data
Client-B, Wait for Data (waitfor)------------------------- ---> Imagine those commands in one "button sub" and no need to have check messsagearrived
Client-B, when all data arrived - show the data

* also imagine that at wait for will append all (possible) splitted bytes transferred from the other Client..



still working on all that... if someone has something to share - will be useful

After some hours... of testing... did some progress... uploading a project to see

When Client-A request data from Client-B (that have the role of server - Be Server: true)...

Client-B sending data with splitting them as limitsizeraw set (at example have it at 100bytes... you can make it smaller or greater to play)
Client-A wait for all data and append bytes...
Client-A when all come... shows at log

Keys:... verify - limitsizeraw - request data

How this example will work:

Compile as stand alone... run two times: run_debug.bat

at first instance: ---> 1) uniqueid: myid1 2)Be Server 3) Start
at second instance: ---> 1) uniqueid: myid2 2) Start 3) Request Data from db server (this will ask for data from first instance)

/ Playing with limitsizeraw - can help with low bandwidth regions - slow internet or many clients.

ps: Caution! This is good example for only two connected mqtt client... if need more you must add Lists for receiving and sending data with id-of-row checking and appending data to any list raw..


I am pretty sure that can be better... and may be easier...