AndroidAdventCalendar2012

MainActivity.java

// Android（サーバ側）

package com.taroid.advent;

import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends Activity {

    private final MessageListener mMessageListener = new MessageListener(9876) {
        @Override
        protected void onReceivedData(final String data) {
            Toast.makeText(getApplicationContext(), data, Toast.LENGTH_LONG).show();
        }
    };

    @Override
    public void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mMessageListener.start();
    }
}

MessageListener.java

// Android（サーバ側）

package com.taroid.advent;

import android.os.Handler;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.Executors;

public abstract class MessageListener {

    private final int mPort;

    private final Handler mHandler;

    private final Runnable mAcceptTask = new Runnable() {
        public void run() {
            final ServerSocket serverSocket;

            try {
                serverSocket = new ServerSocket(mPort);
            } catch (final IOException e) {
                throw new RuntimeException(e);
            }

            final Socket socket;
            try {
                socket = serverSocket.accept();
            } catch (final IOException e) {
                throw new RuntimeException(e);
            } finally {
                try {
                    serverSocket.close();
                } catch (final IOException e) {
                    throw new RuntimeException(e);
                }
            }

            try {
                final InputStream inputStream = socket.getInputStream();
                final String data = readAllLine(inputStream);

                mHandler.post(new Runnable() {
                    public void run() {
                        onReceivedData(data);
                    }
                });
            } catch (final IOException e) {
                throw new RuntimeException(e);
            } finally {
                try {
                    socket.close();
                } catch (final IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    };

    public MessageListener(final int port) {
        mPort = port;
        mHandler = new Handler();
    }

    public void start() {
        Executors.newSingleThreadExecutor().execute(mAcceptTask);
    }

    protected abstract void onReceivedData(String data);

    private static String readAllLine(final InputStream inputStream) throws IOException {
        final BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        final StringBuilder builder = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            builder.append(line);
        }
        return builder.toString();
    }
}

Sample.java

// PC（クライアント側）

package com.taroid.sample;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;

public class Sample {

	public static void main(String[] args) throws IOException {
		try (final Socket socket = new Socket("localhost", 9876)) {
			final OutputStream outputStream = socket.getOutputStream();
			final BufferedWriter writer = new BufferedWriter(
					new OutputStreamWriter(outputStream));
			writer.append("Hello!");
			writer.flush();
		}
	}
}