How to send msg using Socket between two android devices.?

Question

Here is my code

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_server);
    serverStatus = (TextView) findViewById(R.id.server_status);

    SERVERIP = getLocalIpAddress();

    Thread fst = new Thread(new ServerThread());
    fst.start();
}

public class ServerThread implements Runnable {

    public void run() {
        try {
            if (SERVERIP != null) {
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        serverStatus.setText("Listening on IP: " + SERVERIP);
                    }
                });
                serverSocket = new ServerSocket(SERVERPORT);
                while (true) {
                    // listen for incoming clients
                    Socket client = serverSocket.accept();
                    handler.post(new Runnable() {
                        @Override
                        public void run() {
                            serverStatus.setText("Connected.");
                        }
                    });

                    try {
                        BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
                        String line = null;
                        while ((line = in.readLine()) != null) {
                            Log.d("ServerActivity", line);
                            handler.post(new Runnable() {
                                @Override
                                public void run() {
                                    // do whatever you want to the front end
                                    // this is where you can be creative
                                }
                            });
                        }
                        break;
                    } catch (Exception e) {
                        handler.post(new Runnable() {
                            @Override
                            public void run() {
                                serverStatus.setText("Oops. Connection interrupted. Please reconnect your phones.");
                            }
                        });
                        e.printStackTrace();
                    }
                }
            } else {
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        serverStatus.setText("Couldn't detect internet connection.");
                    }
                });
            }
        } catch (Exception e) {
            handler.post(new Runnable() {
                @Override
                public void run() {
                    serverStatus.setText("Error");
                }
            });
            e.printStackTrace();
        }
    }
}

// gets the ip address of your phone's network
private String getLocalIpAddress() {
    try {
        for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
            NetworkInterface intf = en.nextElement();
            for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
                InetAddress inetAddress = enumIpAddr.nextElement();
                if (!inetAddress.isLoopbackAddress()) { 
                    boolean isIPv4 = InetAddressUtils.isIPv4Address(inetAddress.getHostAddress().toString());
                    if(isIPv4)
                    return inetAddress.getHostAddress().toString(); }
            }
        }
    } catch (SocketException ex) {
        Log.e("ServerActivity", ex.toString());
    }
    return null;
}

@Override
protected void onStop() {
    super.onStop();
    try {
         // make sure you close the socket upon exiting
         serverSocket.close();
     } catch (IOException e) {
         e.printStackTrace();
     }
}

Client Side

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

    serverIp = (EditText) findViewById(R.id.server_ip);
    connectPhones = (Button) findViewById(R.id.connect_phones);
    connectPhones.setOnClickListener(connectListener);
}

private OnClickListener connectListener = new OnClickListener() {

    @Override
    public void onClick(View v) {
        if (!connected) {
            Log.e("Clicked", "Yes");
            serverIpAddress = serverIp.getText().toString();
            if (!serverIpAddress.equals("")) {
                Thread cThread = new Thread(new ClientThread());
                cThread.start();
            }
        }
    }
};

public class ClientThread implements Runnable {

    public void run() {
        try {
            InetAddress serverAddr = InetAddress.getByName(serverIpAddress);
            Log.d("ClientActivity", "C: Connecting...");
            Socket socket = new Socket(serverAddr, ServerActivity.SERVERPORT);
            connected = true;
            while (connected) {
                try {
                    Log.d("ClientActivity", "C: Sending command.");
                    PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket
                                .getOutputStream())), true);
                        // where you issue the commands
                        out.println("Hey Server!");
                        Log.d("ClientActivity", "C: Sent.");
                } catch (Exception e) {
                    Log.e("ClientActivity", "S: Error", e);
                }
            }
            socket.close();
            Log.d("ClientActivity", "C: Closed.");
        } catch (Exception e) {
            Log.e("ClientActivity", "C: Error", e);
            connected = false;
        }
    }
}
}

I have used that between two emulators the server is showing that it is listening on 10.0.2.15

But when i go for connection it does not connect

Thers is no error in logcat also i have checked between two physical devices running Android 4.0 with 3G internet Just want to push the android devices running server activity from client activity so that i can perform a action when client send something.

Nothing happens when i click connect button

Permissions:

  <uses-permission android:name="android.permission.INTERNET" />

Answer 1

There's a demo for Bluetooth Chat and WiFi Direct in Android SDK. So you should use Bluetooth or WiFi. I don't think that you can acvhieve direct connection using cellular network.