Send data from Android Phone to ESP32

Question

I am trying to create an android app using Android Studio in order to send some data to an ESP32 in order to display those data on a transparent monitor.

Searching on the web I found several ways to do it but all of them are quite complicated. I was able to search for the paired devices and store the mac address of the ESP32 on my app.

Can anyone help me how to continue from now on ???

Thanks a lot !!

Wachid Susilo · Accepted Answer

1. ESP32 Implementation

Sending data is quite easy. Basically you need to make ESP32 as a Web Server either using native WebServer library or ESPAsyncWebServer library. Here is a quick example using native WebServer library:

#include 
#include 

WebServer server(80);

void handleRoot() {
  server.send(200, "text/plain", "Ready");
}

void handleGet() {
  if (server.hasArg("data")) {
    String data = server.arg("data");
    Serial.println("Data: " + data);
  }
  server.send(200, "text/plain", "Data Received");
}

void handlePost() {
  server.send(200, "text/plain", "Processing Data");
}

void handleUpload() {
  HTTPUpload& upload = server.upload();
  if (upload.status == UPLOAD_FILE_START) {
    Serial.println("Receiving data:");
  } else if (upload.status == UPLOAD_FILE_WRITE) {
    Serial.write(upload.buf, upload.currentSize);
  } else if (upload.status == UPLOAD_FILE_END) {
    server.send(200, "text/plain", "Data: ");
  }
}

void setup() {
  Serial.begin(115200);
  WiFi.softAP("ESP32");
  server.on("/", handleRoot);
  server.on("/get", HTTP_GET, handleGet);
  server.on("/post", HTTP_POST, handlePost, handleUpload);
  server.begin();
}

void loop() {
  server.handleClient();
}

In order to send data to ESP32, you must connect your phone to the same network as ESP32, in this case you can just connect your Android phone to ESP32 Access Point. If you scan available WiFi network in your phone, you should see ESP32. You can check if the Web Server is running using Web Browser. Just type http://192.168.4.1 in address bar and you should get response "ready". In order to send data via HTTP GET method, you can type http://192.168.4.1/get?data=HelloWorld, you will see HelloWorld text in the Serial Monitor.

2. Android Implementation

There is so many HTTP libraries for Android Studio, you may want to check Fast Android Networking. Here is a quick example about how to use it:

build.gradle

dependencies {
    ...
    implementation 'com.amitshekhar.android:android-networking:1.0.2'
    ...
}

activity_main.xml

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        AndroidNetworking.initialize(getApplicationContext());

        Button btnGet = findViewById(R.id.btn_get);
        btnGet.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                /*Send data via HTTP GET*/
                AndroidNetworking.get("http://192.168.4.1/get")
                        .addQueryParameter("data", "HelloWorld")
                        .build()
                        .getAsString(new StringRequestListener() {
                            @Override
                            public void onResponse(String response) {
                                Toast.makeText(getApplicationContext(), response, Toast.LENGTH_SHORT).show();
                            }

                            @Override
                            public void onError(ANError anError) {
                                Toast.makeText(getApplicationContext(), anError.getErrorBody(), Toast.LENGTH_SHORT).show();
                            }
                        });
            }
        });


        Button btnPost = findViewById(R.id.btn_post);
        btnPost.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                /*Send data via HTTP POST*/
                AndroidNetworking.post("http://192.168.4.1/post")
                        .addStringBody("This is my data")
                        .build()
                        .getAsString(new StringRequestListener() {
                            @Override
                            public void onResponse(String response) {
                                Toast.makeText(getApplicationContext(), response, Toast.LENGTH_SHORT).show();
                            }

                            @Override
                            public void onError(ANError anError) {
                                Toast.makeText(getApplicationContext(), anError.getErrorBody(), Toast.LENGTH_SHORT).show();
                            }
                        });
            }
        });
    }
}

Here is how the app looks like:

Whenever you tap GET or POST button, you should see "HelloWorld" or "This is my data" in the Serial Monitor.

That's all. If you want Web Socket Server for faster communication, you can use ESPAsyncWebServer as i mentioned above.

Send data from Android Phone to ESP32

Answers (2)

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