ESP32 RPC response reply only 1.695175409

[sirapol]

I using examples/0010-esp8266_esp32_rpc/0010-esp8266_esp32_rpc.ino .

ESP32 can receive data from rpc request from server. When ESP32 reply , It reply only 1.695175409.

I want it echo data or another thing. Is it bug or my bad ?

[munya-gwena]

I am also facing the same issue with the examples. I just get a different number.

[MathewHDYT]

The serializeJson call should work and simply print a json with a key of "method" and the value "switch_state" and the same again but with the key "params".

For the return value I think there is some kind of misunderstanding, because you don't have to add the "method", or "params" key yourself. That is also never done in the examples. Because that is done automatically over the topic, so those values do not need to be added again.

What happens if you run your code again, but with the other lines commented out and the size decreased to 1, and only doc[RPC_RESPONSE_KEY] = switch_state;, do you then see the correct value?

Because the RPC_Response is meant to return a single value.

[sirapol]

The serializeJson call should work and simply print a json with a key of "method" and the value "switch_state" and the same again but with the key "params".

For the return value I think there is some kind of misunderstanding, because you don't have to add the "method", or "params" key yourself. That is also never done in the examples. Because that is done automatically over the topic, so those values do not need to be added again.

What happens if you run your code again, but with the other lines commented out and the size decreased to 1, and only doc[RPC_RESPONSE_KEY] = switch_state;, do you then see the correct value?

Because the RPC_Response is meant to return a single value.

I try with your suggestion. It same result like picture.

please suggest me.

[sirapol]

And this Tenant is new one very clean. I just add rule node for debug. Rule node is working.

And i try with js client. It working normaly.

[sirapol]

I found something in RPC_Response.cpp Why it nothing to do ?

What should i do ?

[MathewHDYT]

The aforementioned code is correct, because nothing to do is the case, because we do not need to do anything in the constructor body, we do pass the given variable to the base class tough. In this case JsonVariant.

You can ignore that code section, that is not why it is not working correctly.

---

For testing purposes can you replace your return statement with this return RPC_Response(nullptr, switch_state);. It should now show true or false like expected instead of the number as before.

[sirapol]

The aforementioned code is correct, because nothing to do is the case, because we do not need to do anything in the constructor body, we do pass the given variable to the base class tough. In this case JsonVariant.

You can ignore that code section, that is not why it is not working correctly.

For testing purposes can you replace your return statement with this return RPC_Response(nullptr, switch_state);. It should now show true or false like expected instead of the number as before.

It not work. Not replay anything

By the way, I try to debug thingsboard. And I using already code. It log about json. Is it help you ?

[MathewHDYT]

For the previous example, return RPC_Response(nullptr, switch_state);, which value does it show in the cloud? Because from the log message it seems like it should show 1.

If it is 1, then adjust the return to return RPC_Response{nullptr, switch_state}; and see if the value in the cloud is not true.

Additionally the debug messages are helpful, can you attach the debug message for the initial example you had, with the additionally enabled debug mode.

[sirapol]

For the previous example, return RPC_Response(nullptr, switch_state);, which value does it show in the cloud? Because from the log message it seems like it should show 1.

If it is 1, then adjust the return to return RPC_Response{nullptr, switch_state}; and see if the value in the cloud is not true.

Additionally the debug messages are helpful, can you attach the debug message for the initial example you had, with the additionally enabled debug mode.

I try to using return RPC_Response(nullptr, switch_state); It timeout like picture. And not have error from ESP32.

[MathewHDYT]

I think the problem is that the message, in this case without a key, is not sent. Because there is no log message printing that something was sent.

[sirapol]

I think the problem is that the message, in this case without a key, is not sent. Because there is no log message printing that something was sent. Which version of the library are you using?

Thingsboard client sdk : 0.12.0

[MathewHDYT]

Can you adjust the code to something like this:

StaticJsonDocument<JSON_OBJECT_SIZE(1)> doc;
JsonVariant variant = doc.to<JsonVariant>();
variant.set(switch_state);
return RPC_Response(doc);

[sirapol]

Can you adjust the code to something like this:

StaticJsonDocument<JSON_OBJECT_SIZE(1)> doc;
JsonVariant variant = doc.to<JsonVariant>();
variant.set(switch_state);
return RPC_Response(doc);

Ok this work. By the way, If i want add more json key. Is it possible?

[MathewHDYT]

I'll have to try it myself, but as far as I know multiple keys are not possible, you should be able to send one big string containing a json tough.

[sirapol]

I'll have to try it myself, but as far as I know multiple keys are not possible, you should be able to send one big string containing a json tough.

Ok I see. But, In this case is reply the raw message. Is it possible convert to json before send over MQTT.

[MathewHDYT]

I don't think so I'll check if it is possible to return more than one value.

[sirapol]

I try to put json via JsonVariant like below code.

RPC_Response processSwitchChange(const RPC_Data &data)
{
    Serial.println(F("Received the set switch method"));
    // Process data
    const bool switch_state = data[RPC_SWITCH_KEY];
    Serial.print(F("Example switch state: "));
    Serial.println(switch_state);

    // example
    // serializeJsonPretty(data,Serial);
    // Just an response example
    // StaticJsonDocument<JSON_OBJECT_SIZE(1)> doc;
    // doc[RPC_RESPONSE_KEY] = 22.02;
    // return RPC_Response(doc);
    // end example

    StaticJsonDocument<JSON_OBJECT_SIZE(2)> doc;
    char xxxx[] = "{\"params\":{\"data\":\"fromESP32\"}}";
    deserializeJson(doc, xxxx);
    serializeJsonPretty(doc, Serial);
    JsonVariant variant = doc;
    // variant.set(xxxx);
    serializeJsonPretty(variant, Serial);
    return RPC_Response(variant);

    // return RPC_Response(nullptr, switch_state);
}

It output like this.

[sirapol]

I found something. In function process_rpc_message After #ifdef THINGSBOARD_ENABLE_STL response is not corrent. Is it corresponding memory or not ?

I try to pass json to Send_Json_String() it work.

[sirapol]

I verify about this issues. But, I not have idea for solve it. I will tell you.

The first one. RPC_Response before line 1781 is correct from call back. When pass the #if THINGSBOARD_ENABLE_STL. Something override a little bit. such as {"param":"data"} to {"par!@@!":"data"}

Then after line 1792 RPC_Response has only {} Then after line 1794 RPC_Response is null.

I try to by pass this point. It work. Please help implement it.

[MathewHDYT]

I'm not 100% sure what you mean, so if you skip line 1781 to 1792, it works like expected.

And with work like expected you mean that the RPC_Reponse is still {"param":"data"}? Sorry for the confusion

[sirapol]

Hello, After I take my many time.

I think, It has issues about ArduinoJson memory and anything about it.

I let override process_rpc_message like below picture.

And in RPC_Response i do like this.

I not sure, Is it the best practice ? But, It work for me.

I think, It will have problem when you dont need reply json format. But , I don't care lol.

[munya-gwena]

@sirapol I'm trying to replicate your solution and you made use of a function called "splitString()". I can't find any reference of this function.

[sirapol]

@sirapol I'm trying to replicate your solution and you made use of a function called "splitString()". I can't find any reference of this function.

Sorry. It my function.

[munya-gwena]

So I have done all the mods, but it seems there is some key element I'm missing somewhere. The ESP32 reboots after it has built the response topic.

Received the set switch method Example switch state: 0 { "params": { "data": "fromESP32" } }{ "params": { "data": "fromESP32" } }strJsonOut={"params":{"data":"fromESP32"}} resTopic=v1/devices/me/rpc/response/222

abort() was called at PC 0x4013f72b on core 1

Backtrace: 0x40083669:0x3ffcb880 0x4008cd81:0x3ffcb8a0 0x400920f9:0x3ffcb8c0 0x4013f72b:0x3ffcb940 0x4013f772:0x3ffcb960 0x4013f6d3:0x3ffcb980 0x4014125b:0x3ffcb9a0 0x40140302:0x3ffcbc30 0x40140b44:0x3ffcbc50 0x400d4e9a:0x3ffcbc70 0x400d6825:0x3ffcbf10 0x40175029:0x3ffcc050 0x400d7405:0x3ffcc070 0x400d75d5:0x3ffcc0c0 0x400d6261:0x3ffcc0e0 0x400dbe1d:0x3ffcc150

[sirapol]

So I have done all the mods, but it seems there is some key element I'm missing somewhere. The ESP32 reboots after it has built the response topic.

Received the set switch method Example switch state: 0 { "params": { "data": "fromESP32" } }{ "params": { "data": "fromESP32" } }strJsonOut={"params":{"data":"fromESP32"}} resTopic=v1/devices/me/rpc/response/222

abort() was called at PC 0x4013f72b on core 1

Backtrace: 0x40083669:0x3ffcb880 0x4008cd81:0x3ffcb8a0 0x400920f9:0x3ffcb8c0 0x4013f72b:0x3ffcb940 0x4013f772:0x3ffcb960 0x4013f6d3:0x3ffcb980 0x4014125b:0x3ffcb9a0 0x40140302:0x3ffcbc30 0x40140b44:0x3ffcbc50 0x400d4e9a:0x3ffcbc70 0x400d6825:0x3ffcbf10 0x40175029:0x3ffcc050 0x400d7405:0x3ffcc070 0x400d75d5:0x3ffcc0c0 0x400d6261:0x3ffcc0e0 0x400dbe1d:0x3ffcc150

Please try to update ArduinoJson Lib.

[munya-gwena]

After several days of trying out the RPC response, I have managed to get a response back but that is after a small mod in ThingsBoard.h. My observation is it looks like there is a memory leak of some sort. I was able to get it to send responses (with multiple fields) without a problem. The mods I had to do was serialize the "response" to a string the deserialize back to local JsonDocument which is then used to send the response back to the device.

[MathewHDYT]

First of all thanks a lot for your detailed descriptions about the issue and the screenshots. I'm relatively sure I know what the underlying issue is know.

I'll work on a fix, but it will take a while, if a quick fix is required there is no need to change the library. Instead the RPC callback methods have to be changed like shown below.

---

Second of all I am relatively sure it is not a memory leak, that would mean that we are not erasing heap memory even tough we should. I'm pretty sure that is not the case, because the library more or less does not utilise heap memory, especially when THINGSBOARD_ENABLE_DYNAMIC is disabled, which is the case per default.

But what it probably is, is that we are accessing a reference to a local object that has been deleted.

In more detail: We are returning a RPC_Response, which is a JsonVariant. That is nothing more than a reference to a JsonDocument. But the JsonDocument it is pointing too, is erased after we leave the callback scope because it was created only in that method and lies on the stack, therefore we also erase or mangle up our response.

This is the case because stack memory is not really "deleted", but it allows other portions of the code to write into that memory and that would explain the mangled data.

That is probably the reason for the behaviour we saw previously. One way to fix that is to immediately copy the return value from the method to another object, because the data is still on the stack and if we immediately copy it we can "restore" it, but that is also very bad practice and a dirty fix to the problem.

Instead I'll work on a cleaner fix, that instead of returning a reference we instead pass a JsonVariant as one of the arguments and the user can change the sent response over that object. This allows the underlying library to be responsible for the memory instead of the callback method. That should remove the possibility for the aforementioned issue altogether.

---

To test that hypothesis @munya-gwena . It would be nice if you could simply try to allocate the JsonDocument on the global scope instead, which means it will not be erased after the method finishes.

That should also remove the need for the workaround.

StaticJsonDocument<JSON_OBJECT_SIZE(2)> doc;

RPC_Response processTemperatureChange(const RPC_Data &data) {
  doc.clear();
  doc["example1"] = 42;
  doc["example2"] = "test";
  return RPC_Response(doc);
}

[munya-gwena]

Seems you were right on the return value issue. I have made doc a global variable and have not had any issue so far.

[MathewHDYT]

Okay perfect thanks a lot for confirming. For now use that workaround.

I will work on a fix and mention this issue in the pull request once the fix has been completed and is going to be merged.

[sirapol]

Okay perfect thanks a lot for confirming. For now use that workaround.

I will work on a fix and mention this issue in the pull request once the fix has been completed and is going to be merged.

Let close this issues ?