How to properly connect the bluetooth server in C for Android?

    #include <stdio.h>
    #include <unistd.h>
    #include <sys/socket.h>
    #include <bluetooth/bluetooth.h>
    #include <bluetooth/rfcomm.h>
 
    int main(int argc, char **argv)
    {
        struct sockaddr_rc loc_addr = { 0 }, rem_addr = { 0 };
        char buf[1024] = { 0 };
        int s, client, bytes_read;
        socklen_t opt = sizeof(rem_addr);
 
        // allocate socket
        s = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
 
        // bind socket to port 1 of the first available
        // local bluetooth adapter
        loc_addr.rc_family = AF_BLUETOOTH;
        loc_addr.rc_bdaddr = *BDADDR_ANY;
        loc_addr.rc_channel = (uint8_t) 1;
        bind(s, (struct sockaddr *)&loc_addr, sizeof(loc_addr));
 
        // put socket into listening mode
        listen(s, 1);
 
        // accept one connection
        client = accept(s, (struct sockaddr *)&rem_addr, &opt);
 
        ba2str( &rem_addr.rc_bdaddr, buf );
        fprintf(stderr, "accepted connection from %s\n", buf);
        memset(buf, 0, sizeof(buf));
 
        // read data from the client
        bytes_read = read(client, buf, sizeof(buf));
        if( bytes_read > 0 ) {
            printf("received [%s]\n", buf);
        }
 
        // close connection
        close(client);
        close(s);
        return 0;
    }
The source of this example is : http://people.csail.mit.edu/albert/bluez-intro/x502.html

And the class of the app that i am using to connect is:




    import android.bluetooth.BluetoothAdapter;
    import android.bluetooth.BluetoothDevice;
    import android.bluetooth.BluetoothServerSocket;
    import android.bluetooth.BluetoothSocket;
    import android.os.Bundle;
    import android.os.Message;
 
    import java.io.IOException;
    import java.io.InputStream;
    import java.io_OutputStream;
    import java.util.Arrays;
    import java.util.UUID;
 
    public class ConnectionThread extends Thread {
 
 
        BluetoothSocket btSocket = null;
        BluetoothServerSocket btServerSocket = null;
        InputStream input = null;
        OutputStream output = null;
        String btDevAddress = null;
        String myUUID = "00000101-0000-1000-8000-00805F9C34BF";
        boolean server;
        boolean running = false;
        public ConnectionThread() {
 
            this.server = true;
        }
        public ConnectionThread(String btDevAddress) {
 
            this.server = false;
            this.btDevAddress = btDevAddress;
        }
        public void run() {

            this.running = true;
            BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();

            if(this.server) {
                try {
                    btServerSocket = btAdapter.listenUsingRfcommWithServiceRecord("Super Bluetooth", UUID.fromString(myUUID));
                    btSocket = btServerSocket.accept();
                    if(btSocket != null) {
 
                        btServerSocket.close();
                    }
 
                } catch (IOException e) {
                    e.printStackTrace();
                    toMainActivity("---N".getBytes());
                }
 
 
            } else {

                try {

                    BluetoothDevice btDevice = btAdapter.getRemoteDevice(btDevAddress);
                    btSocket = btDevice.createRfcommSocketToServiceRecord(UUID.fromString(myUUID));

                    btAdapter.cancelDiscovery();

                    if (btSocket != null)
                        btSocket.connect();
 
                } catch (IOException e) {
                    e.printStackTrace();
                    toMainActivity("---N".getBytes());
                }
 
            }
 
            if(btSocket != null) {

                toMainActivity("---S".getBytes());
 
                try {
                    input = btSocket.getInputStream();
                    output = btSocket.getOutputStream();
 
                    byte[] buffer = new byte[1024];
                    int bytes;

                    while(running) {
 
                        bytes = input.read(buffer);
                        toMainActivity(Arrays.copyOfRange(buffer, 0, bytes));
 
                    }
 
                } catch (IOException e) {
                    e.printStackTrace();
                    toMainActivity("---N".getBytes());
                }
            }
 
        }
        private void toMainActivity(byte[] data) {
 
            Message message = new Message();
            Bundle bundle = new Bundle();
            bundle.putByteArray("data", data);
            message.setData(bundle);
            MainActivity.handler.sendMessage(message);
        }
        public void write(byte[] data) {
 
            if(output != null) {
                try {
 
                    output.write(data);
 
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } else {
                toMainActivity("---N".getBytes());
            }
        }
 
   
        public void cancel() {
 
            try {
 
                running = false;
                btServerSocket.close();
                btSocket.close();
 
            } catch (IOException e) {
                e.printStackTrace();
            }
            running = false;
        }
    }

To send a data to the server I do:

    ConnectionThread connect = new ConnectionThread(data.getStringExtra("Address_server"));
    connect.start();
    byte[] data = "20".getBytes();
    connect.write(data);