fp MQTT with user/password support ?
lazarus / 38-Networking and Web Programming

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PaulRowntree · 2018-12-02 04:10

Hi!I have been looking for a Laz/fp MQTT package that will connect to
an external MQTT broker; this requires that the package support
username and password fields.  The codes that I have seen most often
(Delphi ported code by Jamie Ingilby, modified by ZiCog, then modified
by heX) [ https://github.com/heX16/mqtt-free-
pascal/blob/master/TMQTTClient/MQTT.pas ] does not support these
fields, although it looks like some initial code was started in this
direction (VariableHeaderConnect ) but not completed and not actually
used in the main code.
Does anyone know of a functioning fp MQTT package with this
capability? 
Thanks!

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DonAlfredo · 2018-12-02 09:14

Have a look at the MQTT connect specs:
https://www.hivemq.com/blog/mqtt-security-fundamentals-authentication-
username-password

You see that you can add a username and password into this connection
request.

Example:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i FH :=
FixedHeader(MQTT.CONNECT, 0, 0, 0);VH :=
VariableHeaderConnect(40);SetLength(Payload, 0);AppendArray(Payload,
StrToBytes(FClientID, true));AppendArray(Payload,
StrToBytes('username', true));AppendArray(Payload,
StrToBytes('password', true));RL := RemainingLength(Length(VH) +
Length(Payload));Data := BuildCommand(FH, RL, VH, Payload);

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PaulRowntree · 2018-12-02 22:59

Hi DonAlfredo, and thank you!  Yes, that is the general way to do it.
There are also 2 bits that need to be set in the FixedHeader, and I
will try this tonight.  Oddly, all versions of the Delphi-forked MQTT
code have this in the ReadThread connect code,

 //  Build CONNECT message
          FH := FixedHeader(MQTT.CONNECT, 0, 0, 0);
          VH := VariableHeaderConnect(40);
          SetLength(Payload, 0);
          AppendArray(Payload, StrToBytes(FClientID, True));
          AppendArray(Payload, StrToBytes('lwt', True));          
          AppendArray(Payload, StrToBytes(FClientID + ' died', True));

          RL := RemainingLength(Length(VH) + Length(Payload));
          Data := BuildCommand(FH, RL, VH, Payload);
(BOLD sections highlighted by me) It looks like 'lwt' and FClientID+'
died' are hard-coded Will topic/message information to be sent if the
connection dies.  Does everyone use this same topic/message, or is
this a vestigial bit of code?

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PaulRowntree · 2018-12-03 06:46

Setting the special bits, and appending fields as DonAlfredo
suggested, works like a charm. 

Will share code if anyone is interested.Thanks!

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Anders Gustav · 2019-02-18 20:46

Quote from: PaulRowntree on December 03, 2018, 07:46:47 am...

Will share code if anyone is interested.Thanks!

Indeed I am!

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Michael Collier · 2025-07-29 12:12

Quote from: PaulRowntree on December 03, 2018, 07:46:47 amSetting the
special bits, and appending fields as DonAlfredo suggested, works like
a charm. 

Will share code if anyone is interested.Thanks!

I'm interested in the solution to this

I can see where to append fields
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
AppendArray(Payload, StrToBytes('username',
true));AppendArray(Payload, StrToBytes('password', true));
But not sure about setting 'special bits' can anyone point me to the
code for that please?

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cdbc · 2025-07-29 12:31

Hi
Saw the title... If you're interested in MQTT, there's a thread HERE,
that points to a complete MQTT-Framework written in FPC/Lazarus repo
on my GitLab, you could have a look at 
Regards Benny