Deserialize Json Document Sent From Web Socket Client to Web Socket Server

[paw1965]

I am hoping someone may be able to help me with a project I am working on, where I send temperature and humidity readings from an ESP8266 web socket client to an ESP32-S3-Touch-LCD-7 web socket server.

The ESP8266 board is set-up as a Async web socket client and the ESP32 board is set-up as Generic web socket server. I am using a AHT10 sensor for the temperature and humidity readings.

Within the program for the client, I have been able to create a Json Document for these readings and serialize this document. I am also able to send this serialized document to the server and see the readings via the serial monitor. However, I am struggling to deserialize the document within the server program. I suspect that, I am not instructing the server to read the serialize document from the client and therefore, the server does not see the document, but I am not sure how to write a suitable argument to instruct the server to read the serialized document.

Could someone kindly suggest how I might go about writing a suitable argument or have any other suggestions?

The ultimate plan for this project is have 3 or 4 more clients send temperature and humidity readings to the server and for these readings to be displayed on the LCD screen.

Many thanks

[Railroader]

Words, words and words. Please read and regard this link: How to get the best out of this forum - Development Tools / IDE 1.x - Arduino Forum

[sonofcy]

See if the following helps

[Dave_Lowther]

I’ve got code for a couple of ESP32 projects which use ESPAsyncWebServer.h and ArduinoJson.h.

In my case it’s a PC sending JSON to the ESP32 to deserialize, but that shouldn’t make any difference.

Perhaps you could post your complete sketch containing the code where you attempt to deserialise the JSON that comes in on the websocket? Then I, or someone else, might be able to offer better help

[sonofcy]

This looks good - JsonParserExample

[PaulRB]

@paw1965

I send temperature and humidity readings from an ESP8266 web socket client to an ESP32-S3-Touch-LCD-7 web socket server...

create a Json Document for these readings and serialize this document.

This seems overkill for the task. Remember, more complexity means lower chance of success. KISS principle.

Why not just send the readings as parameters to a HTTP GET request?

[PerryBebbington]

@paw1965 ,
Maybe this does what you want in terms of providing a means to transfer simple data across an IP connection. Note I am not the expert here but the topic I linked to below probably contains what you need to transfer the data without the complication of JSON.

Link to a very basic tutorial about TCP (evolved to: TCP-socket democode to send / receive data / characters similar to serial

Hi everybody, I'm somehow advanced in programming techniques like non-blocking timing, state-machines, registering and using call-back-functions, using parameters etc. But I'm still a total noob about the subject of clients and servers. Now I'm looking for a very very very basic tutorial about TCP-connections. Whatever I have found so far by googling were demo-codes that immidiately jump up to the level of doing http-requests. I explicitly want to stay below HTTP plain simple sending an…

[kenb4]

@PaulRB

Why not just send the readings as parameters to a HTTP GET request?

I'm old-school: as the verb/word implies, GET should be for retrieval and effectively read-only. A no-body POST with parameters is practically the same to implement. You can't test it by just typing an URL in your browser, which some might consider to be a plus.

@paw1965

I am also able to send this serialized document to the server and see the readings via the serial monitor

Which Serial Monitor: on the client or the server? If you can see/print the JSON on the server, it should be easy to deserialize, as long as you have enough free memory.

If not, you have a client/server problem, not a JSON problem.

[PaulRB]

@kenb4

A no-body POST with parameters is practically the same to implement.

Ah, I learned something new. For some reason I was assuming POST could not have parameters!

But as you say, you cannot easily test sending a POST from your browser like you can with GET, and that's quite inconvenient. You would need to install PostMan or similar and learn to use it.

[paw1965]

Thank you, I will give it a try.

[paw1965]

Thank you for your reply Dave.

I need to tidy up the code for the server before I post it. I hope to be able to do that day.

Thanks again.

[paw1965]

Thank you, I will take a look at this example.

[paw1965]

Thank you, I will take a look.

[paw1965]

Thank you for your response.

I can see the message from the client using the serial monitor on the server but I don't seem to be able to deserialize it.

[paw1965]

WS_Server_Generic.ino (3.7 KB)

Above is a copy of the code for the server without the arduino_secrets.h file.

[Dave_Lowther]

Is this code printing an error?:

if (error) {
    Serial.print(F("deserializeJson() failed: "));
    Serial.println(error.c_str());
    return;

  }

If so can you show what it’s printing?

FWIW: I declare my deserialization doc like this:

static DynamicJsonDocument localDoc(3000); // todo how big does this need to be?

I don’t know a lot about the JSON library API. Just enough to have code that works reliably, but it may not be the best / most elegant use of it.

[paw1965]

Thank you for your prompt reply Dave.

Yes, I get the error “Invalid input”. I have also had the error “Empty input” when I tried something else.
I am using version 7 of ArduinoJson and I have been reading the book that goes with this version, which has a lot of useful information in it. Tomorrow, I will read about what it suggests are the reasons for the invalid input error.

Thanks again.