每次我从 android 应用程序向 esp32 模块发送数据时，它都会以“EmptyInput”的形式到达

问：

我需要将 json 格式的数据从 android 应用程序发送到 esp32 wifi 模块（“arduino”）。

android 应用程序以正确的 json 格式成功发送数据...ESP32 模块知道它接收到一些东西，但它总是作为空输入到达，并因此给我一个错误。

另一方面，当我从 flask 服务器向 esp32 模块发送/接收数据时，它工作正常。与从 flask 服务器向 android 应用程序发送/接收数据相同...有什么建议，或者我在两者之间做错了什么？

这是课堂“大项目”的一部分，并且已经工作了 2 个多月，所以我真的需要它在这里工作。谢谢！

我尝试发送简单的字符串，例如“hey”，其中内容类型设置为“plain”，它仍然作为空字符串到达 esp32......

我在 esp32 模块中有以下内容：

#include <ArduinoJson.h>
#include <WiFi.h>
#include <ESPAsyncWebServer.h>
#include <HTTPClient.h>
#include "AsyncJson.h"

const char* ssid = "wifi_ssid";                //changed these for the post
const char* password = "wifi_password";        //changed these for the post
const unsigned long connectionTimeout = 10000;

AsyncWebServer server(80);

void setup() {
  Serial.begin(115200);

  Serial.print("Connecting to Wifi...");

  // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(1000);
  }
  Serial.print("Connected to WiFi. IP address: ");
  Serial.println(WiFi.localIP());

  //other code stuff...

  // Start server
  //other server.on() stuff...
  server.on("/brew_coffee", HTTP_POST, handleBrewCoffee);
  
  server.begin();
}

void handleBrewCoffee(AsyncWebServerRequest *request) {
  if (request != nullptr) {

    String clientIPAddress = request->client()->remoteIP().toString();

    // Here I receive the data and print it
    String recipeReceived = request->arg("application/json");
    Serial.print("\n" + clientIPAddress);
    Serial.print(" sent string: ");
    Serial.println(recipeReceived);

    DynamicJsonDocument jsonDoc(16386);
    DeserializationError error = deserializeJson(jsonDoc, recipeReceived);

    //This is where I get the EmptyInput error
    if (error) {
      Serial.print("Failed to parse JSON: ");
      Serial.println(error.c_str());
      recipeReceived = "not: " + clientIPAddress;

    } else{
        //Extracting json data
        const char* username = jsonDoc["username"];
        const char* user_ip = jsonDoc["user_ip"];
        const char* user_id = jsonDoc["user_id"];
        const char* name = jsonDoc["name"];
        //I do rest of the data likewise

        // Print the coffee information
        Serial.println("\nCoffee Information:");
        Serial.print("username: "); Serial.println(username);
        Serial.print("user_id: "); Serial.println(user_id);
        Serial.print("Coffee Name: "); Serial.println(name);
        //I do rest of the data likewise
        
        recipeReceived = "Coffee Received";
      }
  }
}

这是我的android应用程序（来自android studio）中发送数据的函数：

    public String makeServiceCallPostJSON(String reqUrl, String username, String user_ip, int user_id, String name, more params...) {

        String response = null;
        try {

            //This url is the same as the esp32 with its proper endpoint
            URL url = new URL(reqUrl);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            conn.setRequestMethod("POST");

            JSONObject jsonParams = new JSONObject();
            jsonParams.put("username", username);
            jsonParams.put("user_ip", user_ip);
            jsonParams.put("user_id", user_id);
            jsonParams.put("name", name);
            //I do rest likewise


            conn.setRequestProperty("Content-Type", "application/json");

            conn.setDoOutput(true);
            conn.setDoInput(true);
            System.out.println(jsonParams.toString());

            conn.getOutputStream().write(jsonParams.toString().getBytes("UTF-8"));

            // read the response
            InputStream in = new BufferedInputStream(conn.getInputStream());

            // Convert the InputStream in a String
            response = convertStreamToString(in);

            System.out.println("This is what i got... " + response);

        } catch (MalformedURLException e) {
            Log.e(TAG, "MalformedURLException: " + e.getMessage());
        } catch (ProtocolException e) {
            Log.e(TAG, "ProtocolException: " + e.getMessage());
        } catch (IOException e) {
            Log.e(TAG, "IOException: " + e.getMessage());
        } catch (Exception e) {
            Log.e(TAG, "Exception: " + e.getMessage());
        }
        return response;
    }

这是我在 esp32 模块中得到的输出

###.#（客户端地址）发送的字符串： 无法解析 JSON：EmptyInput

这些是我在 android studio 的 Logcat 中获得的打印件

{“username”：“guest”，“user_ip”：“###.###.#.###”，“user_id”：1，“name”：“咖啡B”， ...} 这就是我得到的......不

user_ip与 esp32 输出中打印的客户端地址相同。这进一步证明了它“接收”了一些东西，即使它是空的......