ClientTest.java

package main;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.*;
import java.net.Socket;

public class ClientTest {
    private static final int PORT = 1338;
    private static final int TIMEOUT = 2000;

    Server server;
    Thread serverThread;

    @Before
    public void startServer() throws Exception {
        try {
            server = new Server(PORT, TIMEOUT);
            serverThread = new Thread(server);
            serverThread.start();
        } catch (Exception e) {
            e.printStackTrace(System.err);
            throw e;
        }
    }

    @After
    public void shutdownServer() throws InterruptedException {
        if (server != null) {
            server.stopProcessing();
            serverThread.join();
        }
    }

    class TestClient implements Runnable {
        @Override
        public void run() {
            try {
                receiveMessage();
            } catch (IOException ignore) {
                ignore.printStackTrace(System.err);
            }
        }

        private void receiveMessage() throws IOException {
            Socket socket = new Socket("localhost", PORT);
            System.out.println(StringUtils.getMessage(socket));
            socket.close();
        }
    }

    @Test(timeout = 10000)
    public void shouldRunInUnder10Seconds() throws Exception {
        Thread[] threads = new Thread[10];

        for (int i = 0; i < threads.length; ++i) {
            threads[i] = new Thread(new TestClient());
            threads[i].start();
        }

        for (int i = 0; i < threads.length; ++i) {
            threads[i].join();
        }
    }
}

Server.java

package main;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.Date;

public class Server implements Runnable {
    ServerSocket serverSocket;
    volatile boolean listeningForSocketConnections = true;

    public Server(int port, int timeout) throws IOException {
        serverSocket = new ServerSocket(port);
        serverSocket.setSoTimeout(timeout);
    }

    @Override
    public void run() {
        System.out.println("Starting server! :D");

        while (listeningForSocketConnections) {
            listenForSocketConnections();
        }
    }

    private void listenForSocketConnections() {
        try {
            final Socket socket = serverSocket.accept();
            if (socket == null)
                return;

            Runnable clientHandler = new Runnable() {
                @Override
                public void run() {
                    try {
                        StringUtils.sendMessage(socket, new Date().toString());
                        closeIgnoringException(socket);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            };

            Thread clientConnection = new Thread(clientHandler);
            clientConnection.start();
        } catch (IOException e) {
            handle(e);
        }
    }

    private void handle(IOException e) {
        if (!(e instanceof SocketException))
            e.printStackTrace();
    }

    private void closeIgnoringException(Socket socket) throws IOException {
        if (socket != null)
            try {
                socket.close();
            } catch (IOException ignore) {
            }
    }

    public void stopProcessing() {
        System.out.println("Stopping server! :(");

        try {
            listeningForSocketConnections = false;
            serverSocket.close();
        } catch (IOException ignore) {
        }
    }
}

StringUtils.java

package main;

import java.io.*;
import java.net.Socket;

public class StringUtils {
    public static String getMessage(Socket socket) throws IOException {
        InputStream stream = socket.getInputStream();
        ObjectInputStream ois = new ObjectInputStream(stream);
        return ois.readUTF();
    }

    public static void sendMessage(Socket socket, String message) throws IOException {
        OutputStream os = socket.getOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(os);
        oos.writeUTF(message);
        oos.flush();
    }
}