Soketi

//////////// Datagram sockets

public class Server {
        public static void main(String []args){
            try{
                byte[] buffer = new byte[256];
                DatagramSocket socket = new DatagramSocket(1234);
                DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
                System.out.println("Listening for packets...");
                socket.receive(packet);
                System.out.println("Packet recieved! it contains: ");
                for(byte b: packet.getData()){
                    System.out.print((char) b);
                }
            }catch(IOException e){
                System.err.println(e.getMessage());
            }
        }
}

public class Client {
    public static void main(String []args){
        try{
            System.out.println("Connecting to server...");
            Socket socket = new Socket(InetAddress.getByName("localhost"), 1234);

            System.out.println("Connected to server! Writing \"Hello!\" to socket's output stream...");
            // "hello".getBytes()
            socket.getOutputStream().write(new byte[]{'h','e','l','l','o','!'});

            System.out.println("Wrote to the stream! Closing...");
            socket.close();

            System.out.println("Closed! Goodbye :) ");
        }catch(IOException e){
            System.err.print(e.getMessage());
        }
    }
}

//////////// Stream sockets

public class Server {
    public static void main(String []args){
        try{
            System.out.println("Creating server socket at port 1234...");
            ServerSocket serverSocket = new ServerSocket(1234);
          //  System.out.println("Acceptiong client...");
            Socket socket = serverSocket.accept();
          //  System.out.println("Client accepted, wating 5 seconds for buffer...");
            byte [] buffer = new byte[256];
            Thread.sleep(5000);

         //   System.out.println("Reading buffer...");
            socket.getInputStream().read(buffer);
            for(byte b: buffer){
                    System.out.print((char) b);
            }
            System.out.println("That is all, closing socket...");
            socket.close();
         //   System.out.println("Aufviedersehn!");
        }catch(IOException e){
            System.err.print(e.getMessage());
        }catch(InterruptedException e){
            System.err.print(e.getMessage());
        }
    }
}

public class Client {
    public static void main(String []args){
        try{
            System.out.println("Connecting to server...");
            Socket socket = new Socket(InetAddress.getByName("localhost"), 1234);

            System.out.println("Connected to server! Writing \"Hello!\" to socket's output stream...");
            // "hello".getBytes()
            socket.getOutputStream().write(new byte[]{'h','e','l','l','o','!'});

            System.out.println("Wrote to the stream! Closing...");
            socket.close();

            System.out.println("Closed! Goodbye :) ");
        }catch(IOException e){
            System.err.print(e.getMessage());
        }
    }
}

//////////// NIO

public class Client {

    public static void main(String[] args) throws IOException {
        SocketAddress address = new InetSocketAddress(InetAddress.getByName("localhost"), 9090);
        SocketChannel channel = SocketChannel.open(address);

        Thread nit = new Thread(new Runnable() {

            @Override
            public void run() {
                ByteBuffer podaciSaServera = ByteBuffer.allocate(256);
                podaciSaServera.clear();

                while (true) {
                    try {
                        channel.read(podaciSaServera);
                        podaciSaServera.flip();
                        System.out.println();
                        while (podaciSaServera.hasRemaining()) {
                            System.out.print((char)podaciSaServera.get());
                        }
                        System.out.println();
                        podaciSaServera.clear();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        });

        nit.start();

        /// slanje na server
        Scanner scanner = new Scanner(System.in);
        ByteBuffer buffer = ByteBuffer.allocate(256);
        while(true)
        {
            String line = scanner.nextLine();
            buffer.put(line.getBytes());
            buffer.flip();
            channel.write(buffer);
            buffer.clear();
        }
    }
}

public class Server {

    static int port = 9090;
    static ServerSocketChannel ssc = null;
    static Selector selector = null;
    public static void main(String[] args) throws IOException {

        ssc = ServerSocketChannel.open();
        ServerSocket socket = ssc.socket();
        InetSocketAddress isa = new InetSocketAddress(port);
        socket.bind(isa);

        ssc.configureBlocking(false); // vazno
        selector = Selector.open();
        ssc.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("Server is started at port: "+ port);

        while(true)
        {
            selector.select();
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> kljucevi = selectionKeys.iterator();

            while (kljucevi.hasNext()) {
                SelectionKey selectionKey = (SelectionKey) kljucevi.next();
                kljucevi.remove();
                if(selectionKey.isAcceptable())
                {
                    ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
                    SocketChannel klijentskiKanal = serverSocketChannel.accept();
                    klijentskiKanal.configureBlocking(false);
                    String ip_adresa = klijentskiKanal.socket().getInetAddress()
                                        + ":" + klijentskiKanal.socket().getPort();

                    klijentskiKanal.register(selector, SelectionKey.OP_READ, ip_adresa);
                }
                else if (selectionKey.isReadable())
                {
                    SocketChannel klijent = (SocketChannel) selectionKey.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(256);
                    buffer.clear();

                    // citanje iz kanala
                    klijent.read(buffer);
                    buffer.flip();

                    String poruka = selectionKey.attachment() + " ";
                    while (buffer.hasRemaining()) {
                        poruka += (char)buffer.get();
                    }
                    posaljiSvima(poruka);
                }
            }
        }
    }

    private static void posaljiSvima(String poruka) throws IOException
    {
        ByteBuffer buffer = ByteBuffer.wrap(poruka.getBytes());

        for(SelectionKey kljuc: selector.keys())
        {
            if(kljuc.isValid() && kljuc.channel() instanceof SocketChannel)
            {
                SocketChannel klijent = (SocketChannel)kljuc.channel();
                klijent.write(buffer);
                buffer.rewind();
            }
        }
    }
}

//////////// RMI
public class Klijent
{
    public static void main(String[] args)
    {
        try
        {
            System.out.println("Konektovanje na server....");

            BrojacI server = (BrojacI)Naming.lookup("rmi://localhost/Server");

            System.out.println("Brojac: " + server.count());

        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
}

public class Server
{
      public static void main(String[] args)
      {
          try
          {
              Brojac brojac = new Brojac();
              LocateRegistry.createRegistry(1099);
              Naming.rebind("//localhost:1099/Server", brojac);

              System.out.println("Server je startovan.");

          }
          catch (Exception ex)
          {
              ex.printStackTrace();
          }
      }
}

public class Brojac extends UnicastRemoteObject implements BrojacI
{
    private static final long serialVersionUID = -117253489961899775L;
    private int count = 0;

    public Brojac() throws RemoteException
    {
    }

    public int count() throws RemoteException
    {
        return ++count;
    }
}

public interface BrojacI extends Remote
{
    public int count() throws RemoteException;
}

//////////// Multicast UDP
public class Server {
    public static void main(String[] args) {
        int socketPort = Common.SOCKET_PORT;
        try {
            InetAddress adress = InetAddress.getByName(Common.ADDRESS); // group
            MulticastSocket socket = new MulticastSocket(socketPort);
            socket.setTimeToLive(1);
            socket.joinGroup(adress);

            while (true) {
                String poruka = "Pozdrav svima";
                byte[] data = poruka.getBytes();
                DatagramPacket packet = new DatagramPacket(data, data.length, adress, socketPort);
                socket.send(packet);
                System.out.println("Poslao podatke");
                Thread.sleep(5000);
            }
        } catch (IOException e) {
            //TODO: handle exception
        }catch (Exception e) {
            //TODO: handle exception
        }
    }
}

public class Client {
    public static void main(String[] args) {
        int socketPort = Common.SOCKET_PORT;
        try {
            InetAddress address = InetAddress.getByName(Common.ADDRESS);
            MulticastSocket socket = new MulticastSocket(socketPort);
            socket.joinGroup(address);
            byte[] data = new byte[1024];
            while (true) {
                DatagramPacket dp = new DatagramPacket(data, data.length, address, socketPort);
                socket.receive(dp);
                String poruka = new String(dp.getData());
                System.out.println(poruka.trim());
            }

        } catch (Exception e) {
            //TODO: handle exception
        }
    }
}

public class Common {
    public static int SOCKET_PORT = 5776;
    public static String ADDRESS = "228.5.6.7";
}