Java, klient/server socket.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Connection implements Runnable
{
    private int myPortNr;
    private String remote;
    private int toPortNr;
    private Draw draw = null;
    private Socket socket = null;
    private PrintWriter out = null;

    public Connection (Draw draw, int myPortNr, int toPortNr, String remote)
    {
        this.draw = draw;
        this.myPortNr = myPortNr;
        this.remote = remote;
        this.toPortNr = toPortNr;

        new Thread (this).start ();
    }

    public void sendData (String str) throws IOException
    {
        socket = new Socket (this.remote, this.toPortNr);
        out = new PrintWriter (socket.getOutputStream (), true);
        out.println (str);

        out.close ();
        socket.close ();
    }

    public void run ()
    {
        String str = "";
        Socket socketIncoming = null;
        BufferedReader in = null;
        ServerSocket serverSocket = null;
        
        try
        {
            serverSocket = new ServerSocket (this.myPortNr);

            while (true)
            {
                socketIncoming = serverSocket.accept ();
                in = new BufferedReader (new InputStreamReader
                        (socketIncoming.getInputStream ()));

                str = in.readLine ();

                if (str.length () <= 5)
                    draw.addClearAllLines (str);
                else if (str.length () <= 10)
                    draw.addEraseLine (str);
                else
                    draw.addLine (str);
            }
        }
        catch (IOException ex)
        {
            ex.printStackTrace ();
        }
        finally
        {
            try
            {
                in.close ();
                socketIncoming.close ();
                serverSocket.close ();
            } 
            catch (IOException ex)
            {
                ex.printStackTrace ();
            }
        }
    }
}