Hi,
I'm extending an old daemon so it writes the data to MQTT, using mosquitto_pub.
To have a correct message (-m ...) I need to include double-quotes. But it seems ExecuteProcess(exec,cmdline) splits the cmdline according some rules if it's a single string.
When I tried to do it in a single string :
-h 127.0.0.1 -t solartopic -u user -P secret -i clientid -m "{\"Pac\": 458.00}"
I got :
Error: Unknown option 'Pac\":'.
So I need to make cmdline an array. How I do that ? I tried :

  MQTTStr : array [0..5] of ansistring;

...

  MQTTStr[0]:='-h '+MQTTBroker;
  MQTTStr[1]:='-t '+MQTTTopic;
  MQTTStr[2]:='-u '+MQTTUser;
  MQTTStr[3]:='-P '+MQTTPassw;
  MQTTStr[4]:='-i '+MQTTClientID;
  MQTTStr[5]:='-m "{\"'+ChanName+'\": '+TextValue+'}"';
  ExecuteProcess(MQTTExec,MQTTStr));

But then :
Error: Unknown option '-h 127.0.0.1'.
Use 'mosquitto_pub --help' to see usage.

Thanks in advance

Koenraad

Hi,

Just a guess, but I think you need to do:

MQTTStr[0]:='-h';
MQTTStr[1]:=MQTTBroker;
MQTTStr[2]:='-t';
MQTTStr[3]:=MQTTTopic;
... etc.
MQTTStr[n]:='-m';
MQTTStr[n+1]:=MQTTMessage;

Like this. It's maybe a bit counter intuitive, but you have to think from the perspective of the other app, everything which you put into 1 string will go into 1 "slot" of its "ParamStr(x)". And then it's maybe more obvious how you need to split your arguments.

BTW, shameless plug, but this is a very very hacky way to talk to an MQTT broker I think, I've made a raw C header conversion, and a Pascal-style multithreaded OOP wrapper for libmosquitto, so you can properly integrate MQTT communication in your Free Pascal app (tested on Linux, MacOS and Windows):

https://github.com/chainq/mosquitto-p

I'm not sure of the complexity of what you want to do, but for anything remotely more complex, than sending 1 message every minute or so, this might be a better solution than trying to squeeze things through mosquitto_pub's arguments.

Cheers,

El 25/8/20 a les 14:31, Koenraad Lelong via fpc-pascal ha escrit:

Hi, I'm extending an old daemon so it writes the data to MQTT, using mosquitto_pub.

Not what you're asking, but did you try to send the messages yourself instead of using mosquitto_pub?
I didn't try it, but there's

https://github.com/heX16/mqtt-free-pascal

Bye

Hi,
Thanks for the suggestion I will try that array.

Why I did it like that : I thought it an easy and fast way to enhance my project. I added the same value to rrd, the same way, i.e. a ExecuteProcess with a bunch of parameters. There it works, but no double quotes needed.

LAter I will try your wrapper.

Op 25/08/2020 om 15:52 schreef Karoly Balogh (Charlie/SGR) via fpc-pascal:

...

Hi,

Thanks for the reply, I did know of that project. The thing is, at the moment I don't know how to implement that in my project. I'm still studying this.

Op 25/08/2020 om 15:55 schreef Luca Olivetti via fpc-pascal:

FWIW,

That array did the trick. Thanks again.
But I'll study the wrapper in the near future.

Op 25/08/2020 om 18:18 schreef Koenraad Lelong via fpc-pascal: