Implementation of Android command interpreter (usable via telnet for instance).

CmdService.java

package com.example.sdabet.test;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.Log;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;

public class CmdService extends Service {

    private static final String LOG_TAG = CmdService.class.getSimpleName();

    private static final int PORT = 3000;

    private final CmdThread cmdThread = new CmdThread(this, PORT);

    @Override
    public void onCreate() {
        Log.d(LOG_TAG, "onCreate()");
        cmdThread.start();
    }

    @Override
    public void onDestroy() {
        Log.d(LOG_TAG, "onDestroy()");
        try {
            cmdThread.terminate();
            cmdThread.join();
        } catch (InterruptedException e) {
            Log.e(LOG_TAG, "onDestroy: failed to stop command thread", e);
        }
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

CmdThread.java

package com.example.sdabet.test;

import android.content.Context;
import android.content.Intent;
import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Collections;
import java.util.List;

public class CmdThread extends Thread {

    private static final String LOG_TAG = CmdThread.class.getSimpleName();

    private static final String CMD_EXIT = "exit", CMD_ACTIVITY = "activity";

    private final int port;

    private ServerSocket server;

    private Socket socket;

    private final Context context;

    public CmdThread(Context context, int port) {
        super(LOG_TAG);
        this.context = context;
        this.port = port;
    }

    @Override
    public void run() {
        try {
            server = new ServerSocket(port);
            Log.d(LOG_TAG, "Server started on " + getIPAddress(true) + ":" + port);
            while(!isInterrupted()) {
                socket = server.accept();
                Log.d(LOG_TAG, "New connection accepted from " + socket.getInetAddress());
                PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
                BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String cmd;
                while (!isInterrupted() && (cmd = reader.readLine()) != null) {
                    Log.d(LOG_TAG, "Received '" + cmd + "'");
                    String[] args = cmd.split(" ");
                    if (CMD_EXIT.equals(cmd)) {
                        writer.println("Goodbye!");
                        break;
                    } else if(CMD_ACTIVITY.equals(args[0])) {
                        if(args.length != 2) {
                            writer.println("Usage: 'activity <activity_name>'");
                        }
                        else {
                            try {
                                Class activity = Class.forName(args[1]);
                                writer.println("Starting activity " + args[1]);
                                Intent intent = new Intent(context, activity);
                                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                                context.startActivity(intent);
                            } catch (ClassNotFoundException e) {
                                writer.println("Invalid activity '" + args[1] + "'");
                            }
                        }
                    } else {
                        writer.println("Unknown command");
                    }
                }
                Log.d(LOG_TAG, "Closing current connection...");
                socket.close();
                Log.d(LOG_TAG, "Current connection closed");
            }
            Log.d(LOG_TAG, "Stopping server...");
            server.close();
            Log.d(LOG_TAG, "Server stopped");
        } catch (IOException e) {
            Log.d(LOG_TAG, "Server terminated");
        }
    }

    public void terminate() {
        Log.d(LOG_TAG, "terminate()");
        try {
            if(socket != null) socket.close();
            if(server != null) server.close();
        } catch (IOException e) {
            Log.e(LOG_TAG, "terminate: error", e);
        }
    }

    /**
     * Get IP address from first non-localhost interface
     * @param useIPv4  true=return ipv4, false=return ipv6
     * @return  address or empty string
     */
    private static String getIPAddress(boolean useIPv4) {
        try {
            List<NetworkInterface> interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
            for (NetworkInterface intf : interfaces) {
                List<InetAddress> addrs = Collections.list(intf.getInetAddresses());
                for (InetAddress addr : addrs) {
                    if (!addr.isLoopbackAddress()) {
                        String sAddr = addr.getHostAddress();
                        //boolean isIPv4 = InetAddressUtils.isIPv4Address(sAddr);
                        boolean isIPv4 = sAddr.indexOf(':')<0;

                        if (useIPv4) {
                            if (isIPv4)
                                return sAddr;
                        } else {
                            if (!isIPv4) {
                                int delim = sAddr.indexOf('%'); // drop ip6 zone suffix
                                return delim<0 ? sAddr.toUpperCase() : sAddr.substring(0, delim).toUpperCase();
                            }
                        }
                    }
                }
            }
        } catch (Exception ex) { } // for now eat exceptions
        return "";
    }
}