Give an example of publish with retained bit set

[raenrfm]

I'm trying to send payloads that I want retained, but I cannot figure out the syntax of the publish statement to allow that. I'm using QOS0 so don't care about that.

[hirotakaster]

@raenrfm
you use this function.
bool publish(const char *topic, const uint8_t *payload, unsigned int plength, bool retain);

[raenrfm]

This is the modified callback function correct? But how is it used in the sketch? Is it just the client.publish(topic,payload); command? Do I have to pass anything else in this command or is modifying the callback function enough?

[hirotakaster]

@raenrfm
If you want to use retain flag use this, but I don't know what you want to do.

[raenrfm]

But how is it used in the sketch? Can you just show me a sketch that publishes with the retained bit set to true? I want my MQTT server to retain values even if they have been read by one device. I want the value to stay in the server until a new value replaces it. That is what the retained message is for.

[hirotakaster]

yes, you set "retain = true" like this publish("/topic", "hoge", 4, true); .
This library is OSS(MIT), so you can see source code by yourself, and if you need more function or implementation please send a diff/pull request.

[onsimon]

@hirotakaster I've studied the source code but can't get this to work either, tried casting input values to different types without success. Particle compile service returns this:

call of overloaded 'publish(const char[18], const char[3], int, bool)' is ambiguous

[onsimon]

Use case for me is setting up an remote switch integration with Home Assistant (docs). The retain flag is used to feed back status after switching on/off.

Example topic="bedroom/light/status", payload="ON"

[onsimon]

Darn.. the curse of posting questions. After looking one more time at the source I noticed the small type difference of the payload, this works for me now:

client.publish("bedroom/light/status", (uint8_t*) "ON", 2, true);

Ping @raenrfm in case you haven't solved it

[raenrfm]

Ok so the addition of the (uint8_t*) is what solved the issue?

On Fri, Dec 1, 2017, 5:53 PM Simon Hellbe, ***@***.***> wrote: Darn.. the curse of posting questions. After looking one more time at the source I noticed the small type difference of the payload, this works for me now: client.publish("bedroom/light/status", (uint8_t*) "ON", 2, true); Ping @raenrfm <https://github.com/raenrfm> in case you haven't solved it — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#68 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AX9UrvJ5IZw694cPAI7QzfUK4_piu0Yzks5s8INZgaJpZM4QJG6y> .

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[onsimon]

Yep @raenrfm

[raenrfm]

Would this apply if your payloads are just unsigned integers?

On Sat, 2 Dec 2017 at 17:34 Simon Hellbe ***@***.***> wrote: Yep @raenrfm <https://github.com/raenrfm> — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#68 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AX9UrsqV4cq5PHV5yaEs2erE1m82rr6Pks5s8dBkgaJpZM4QJG6y> .

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[raenrfm]

Sorry what I meant was that I'm using this on a particle photon and have the payloads set as unsigned int's

On Wed, 6 Dec 2017 at 09:48 Robert Mantel ***@***.***> wrote: Would this apply if your payloads are just unsigned integers? On Sat, 2 Dec 2017 at 17:34 Simon Hellbe ***@***.***> wrote: > Yep @raenrfm <https://github.com/raenrfm> > > — > You are receiving this because you were mentioned. > Reply to this email directly, view it on GitHub > <#68 (comment)>, > or mute the thread > <https://github.com/notifications/unsubscribe-auth/AX9UrsqV4cq5PHV5yaEs2erE1m82rr6Pks5s8dBkgaJpZM4QJG6y> > . > --

<object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[raenrfm]

I really wish he created an example of using the retained feature. I'm still having trouble getting this to work.

On Wed, 6 Dec 2017 at 09:51 Robert Mantel ***@***.***> wrote: Sorry what I meant was that I'm using this on a particle photon and have the payloads set as unsigned int's On Wed, 6 Dec 2017 at 09:48 Robert Mantel ***@***.***> wrote: > Would this apply if your payloads are just unsigned integers? > > On Sat, 2 Dec 2017 at 17:34 Simon Hellbe ***@***.***> > wrote: > >> Yep @raenrfm <https://github.com/raenrfm> >> >> — >> You are receiving this because you were mentioned. >> Reply to this email directly, view it on GitHub >> <#68 (comment)>, >> or mute the thread >> <https://github.com/notifications/unsubscribe-auth/AX9UrsqV4cq5PHV5yaEs2erE1m82rr6Pks5s8dBkgaJpZM4QJG6y> >> . >> > -- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[onsimon]

I think you're ok as long as you're not overflowing it with a high number, uint8_t is short for an unsigned 8 bit integer (i.e. 0-255). But I'm kind of out of my depth here :)

[onsimon]

Check out this thread for converting high ints to uint8_t arrays: https://forum.arduino.cc/index.php?topic=361659.0

[raenrfm]

yeah, it's working without the retained setup, but I don't know what callback function to use to publish a retained payload.

On Wed, 6 Dec 2017 at 10:12 Simon Hellbe ***@***.***> wrote: I think you're ok as long as you're not overflowing it with a high number, uint8_t is short for an unsigned *8 bit* integer (i.e. 0-255). But I'm kind of out of my depth here :) — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#68 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AX9UruVQWEvi8_4ME55Zw2Qr7aukmnAoks5s9q7FgaJpZM4QJG6y> .

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[raenrfm]

He has three example ino files but none of them show the use of the retained bit.

On Wed, 6 Dec 2017 at 10:15 Robert Mantel ***@***.***> wrote: yeah, it's working without the retained setup, but I don't know what callback function to use to publish a retained payload. On Wed, 6 Dec 2017 at 10:12 Simon Hellbe ***@***.***> wrote: > I think you're ok as long as you're not overflowing it with a high > number, uint8_t is short for an unsigned *8 bit* integer (i.e. 0-255). > But I'm kind of out of my depth here :) > > — > You are receiving this because you were mentioned. > Reply to this email directly, view it on GitHub > <#68 (comment)>, > or mute the thread > <https://github.com/notifications/unsubscribe-auth/AX9UruVQWEvi8_4ME55Zw2Qr7aukmnAoks5s9q7FgaJpZM4QJG6y> > . > -- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[onsimon]

You might need to clarify your use case more. The original question was just about publishing with retained flag but now you're talking about callbacks?

I provided an example how to publish with a retained bit in this comment. If you have a high int as the payload the recommendation from the arduino forum thread I linked before is to convert your int to a string and then back to int on the receiving end.

[raenrfm]

If you don't use the correct callback function you can't use the retained bit capability, from what I understand.

On Wed, 6 Dec 2017 at 10:20 Simon Hellbe ***@***.***> wrote: You might need to clarify your use case more. The original question was just about publishing with retained flag but now you're talking about callbacks? I provided an example how to publish with a retained bit in this comment <#68 (comment)>. If you have a high int as the payload you want to suggest the recommendation from the arduino forum thread I linked before is to convert your int to a string and then back to int on the receiving end. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#68 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AX9Urv0BiTutKaJJtvSnZmb17Kh4vTQlks5s9rCjgaJpZM4QJG6y> .

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[raenrfm]

Here is the callback function used in his example: void callback(char* topic, byte* payload, unsigned int length); if you attempt to use this with the retained bit option in your publish statement it blows up.

On Wed, 6 Dec 2017 at 10:24 Robert Mantel ***@***.***> wrote: If you don't use the correct callback function you can't use the retained bit capability, from what I understand. On Wed, 6 Dec 2017 at 10:20 Simon Hellbe ***@***.***> wrote: > You might need to clarify your use case more. The original question was > just about publishing with retained flag but now you're talking about > callbacks? > > I provided an example how to publish with a retained bit in this comment > <#68 (comment)>. > If you have a high int as the payload you want to suggest the > recommendation from the arduino forum thread I linked before is to convert > your int to a string and then back to int on the receiving end. > > — > You are receiving this because you were mentioned. > Reply to this email directly, view it on GitHub > <#68 (comment)>, > or mute the thread > <https://github.com/notifications/unsubscribe-auth/AX9Urv0BiTutKaJJtvSnZmb17Kh4vTQlks5s9rCjgaJpZM4QJG6y> > . > -- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[raenrfm]

I'm converting floats to strings then publishing. I'm thinking that's the difference between your case and mine.

On Wed, 6 Dec 2017 at 10:26 Robert Mantel ***@***.***> wrote: Here is the callback function used in his example: void callback(char* topic, byte* payload, unsigned int length); if you attempt to use this with the retained bit option in your publish statement it blows up. On Wed, 6 Dec 2017 at 10:24 Robert Mantel ***@***.***> wrote: > If you don't use the correct callback function you can't use the retained > bit capability, from what I understand. > > On Wed, 6 Dec 2017 at 10:20 Simon Hellbe ***@***.***> > wrote: > >> You might need to clarify your use case more. The original question was >> just about publishing with retained flag but now you're talking about >> callbacks? >> >> I provided an example how to publish with a retained bit in this comment >> <#68 (comment)>. >> If you have a high int as the payload you want to suggest the >> recommendation from the arduino forum thread I linked before is to convert >> your int to a string and then back to int on the receiving end. >> >> — >> You are receiving this because you were mentioned. >> Reply to this email directly, view it on GitHub >> <#68 (comment)>, >> or mute the thread >> <https://github.com/notifications/unsubscribe-auth/AX9Urv0BiTutKaJJtvSnZmb17Kh4vTQlks5s9rCjgaJpZM4QJG6y> >> . >> > -- > <object width="290" height="130"><param name="movie" value=" > http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" > /><embed src=" > http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" > type="application/x-shockwave-flash" width="290" height="130" /></object> > -- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

-- <object width="290" height="130"><param name="movie" value=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" /><embed src=" http://www.wunderground.com/swf/pws_mini_rf_nc.swf?station=ITHUNDER5&freq=&units=metric&lang=EN" type="application/x-shockwave-flash" width="290" height="130" /></object>

[dakl]

FYI, I added a method like so:

bool MQTT::publish(const char* topic, const char* payload, bool retain) {
    return publish(topic, (uint8_t*)payload, strlen(payload), retain, QOS0, NULL);
}

With this, I just do client.publish("someTopic", "ON", true); to send a message with the retain flag.

I'm happy to provide a PR if it's useful to the community @hirotakaster

[hirotakaster]

Hi @dakl ,
Thank you!! Of course, PR welcome:)

[dakl]

#77 should fix this. @raenrfm @hirotakaster