Send a message from app (Android Studio) to NodeMCU (Arduino Serial Monitor) by using socket programming - Stack Overflow

admin2025-04-17 3

I want to send a message from android app to NodeMCU. Here is the codes :

Android Studio (MainActivity.java) :

package com.send.client.socket;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import java.io.IOException;
import java.io.PrintWriter;
import java.Socket;

public class MainActivity extends AppCompatActivity {

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

    public void btnSendOnClick(View v) {
        Thread send = new Thread() {
            @Override
            public void run() {
                try {
                    Socket socket = new Socket("192.168.1.1", 4444);
                    PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
                    writer.println("Hellow World");
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        send.start();
    }
}

NodeMCU (Arduino.ino) :

#include <ESP8266WiFi.h>

const char ssid[] = "NodeMCU" ;
const char pass[] = "12345678";
char ch;
String msg;

IPAddress ip(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
WiFiServer server(4444);
WiFiClient client;

void setup()
{
  Serial.begin(9600);

  WiFi.mode(WIFI_AP);
  WiFi.softAP(ssid, pass);
  delay(100);
  WiFi.softAPConfig(ip, ip, subnet);
  server.begin();
}

void loop()
{
  client = server.available();

  if (client.available() > 0)
  {
    ch = NULL;
    msg = "";

    while (client.available() > 0)
    {
      ch = client.read();
      msg += ch;
    }
    Serial.print(msg);
  }
}

The codes works to some extent but it is unstable, I have to tap the send button of app a lot of times (10 times or so) in order to send one message! I am sure about NodeMCU side because by using another C# socket programming I can send the message instantly.

I want to send a message from android app to NodeMCU. Here is the codes :

Android Studio (MainActivity.java) :

package com.send.client.socket;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;

public class MainActivity extends AppCompatActivity {

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

    public void btnSendOnClick(View v) {
        Thread send = new Thread() {
            @Override
            public void run() {
                try {
                    Socket socket = new Socket("192.168.1.1", 4444);
                    PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
                    writer.println("Hellow World");
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        send.start();
    }
}

NodeMCU (Arduino.ino) :

#include <ESP8266WiFi.h>

const char ssid[] = "NodeMCU" ;
const char pass[] = "12345678";
char ch;
String msg;

IPAddress ip(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
WiFiServer server(4444);
WiFiClient client;

void setup()
{
  Serial.begin(9600);

  WiFi.mode(WIFI_AP);
  WiFi.softAP(ssid, pass);
  delay(100);
  WiFi.softAPConfig(ip, ip, subnet);
  server.begin();
}

void loop()
{
  client = server.available();

  if (client.available() > 0)
  {
    ch = NULL;
    msg = "";

    while (client.available() > 0)
    {
      ch = client.read();
      msg += ch;
    }
    Serial.print(msg);
  }
}

Share Improve this question edited Jan 31 at 14:45 Robert 43k18 gold badges109 silver badges172 bronze badges Recognized by Mobile Development Collective asked Jan 31 at 8:50 Farid 334 bronze badges

You should close the socket after you have used it. I would also recommend to add logging code before and after the socket code and then check logcat while you use the app. – Robert Commented Jan 31 at 14:44

Add a comment |

1 Answer 1

Sorted by: Reset to default 0

You should make sure that network requests are asynchronous, and performing network operations on the main thread can easily cause the interface to get stuck or unresponsive

    public void btnSendOnClick(View v) {
    executorService.execute(new Runnable() {
        @Override
        public void run() {
            Socket socket = null;
            PrintWriter writer = null;
            try {
                socket = new Socket("192.168.1.1", 4444);
                writer = new PrintWriter(socket.getOutputStream(), true);
                writer.println("Hello World");
            } catch (IOException e) {
                e.printStackTrace();
            } finally {                 
                if (writer != null) {
                    writer.close();
                }
                if (socket != null) {
                    try {
                        socket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    });
}

Then close at the end

@Override
protected void onDestroy() {
    super.onDestroy();
    executorService.shutdown(); 
}

You can also try using Kotlin's coroutine, which is very convenient

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