source: java-rpg-common/Connection.java

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

/*
 * This class serves as a basis for the threads that the other projects use to listen to incoming messages over a network. The most important
 * method, run, initializes a connection based on the constructor arguments and calls different methods depending on the result, which could
 * range from a successful connection, to an unsuccessful one, to one that gets interrupted later on. Any class inheriting this one simply
 * has to extend the methods called in run and the processMessage method to customize the behavior in different situations.
 */

public class Connection extends Thread {
        private boolean connected;
        private boolean interrupted;
        private String ip;
        private int port;
    private Socket socket;
    private PrintWriter out;
    private BufferedReader in;

    public Connection(String ip, int port, String threadName) {
        super(threadName);
        
        connected = false;
        interrupted = false;
        socket = null;
        this.ip = ip;
        this.port = port;
    }
    
    public Connection(Socket socket, String threadName) {
        super(threadName);
        
        connected = false;
        interrupted = false;
        this.socket = socket;
    }
    
    public static boolean isConnected(Connection obj) {
        return obj != null && obj.connected;
    }
    
    protected PrintWriter getOut() {
        return out;
    }
    
    protected BufferedReader getIn() {
        return in;
    }
    
    public void interrupt() {
        interrupted = true;
    }
    
    public void closeConnection() {
        try {
                if(connected) {
                        connected = false;
                        socket.close();
                        out.close();
                        in.close();
                }
        } catch(IOException ioe) {
                ioe.printStackTrace();
        }
    }
    
    protected void sendMessage(MessageType type, String input) {
                out.println(type);
                out.println(input);
    }
    
    protected void processMessage(MessageType type, String input) {
        
    }
    
    protected void connectionStart() {
        
    }
    
    protected void connectionSuccess() {
        
    }
    
    protected void connectionFailure() {
        
    }
    
    protected void connectionBreak() {
        
    }
    
    protected void peerDisconnect() {
        
    }
    
    protected void connectionEnd() {
        
    }
    
    public void run() {
        String strType, str;
        
        try {
                connectionStart();
                if(socket == null)
                        socket = new Socket(ip, port);
                if(!interrupted) {
                        out = new PrintWriter(socket.getOutputStream(), true);
                        in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                connected = true;
                connectionSuccess();
                }
        }catch (UnknownHostException uhe) {
                if(!interrupted)
                        connectionFailure();
        }catch (ConnectException ce) {
                if(!interrupted)
                        connectionFailure();
        }catch(IOException ioe) {
                if(!interrupted)
                        ioe.printStackTrace();
        }
        
        if(interrupted)
                closeConnection();
                
        try{
                while(connected && (strType = in.readLine()) != null && (str = in.readLine()) != null) {
                        processMessage(MessageType.valueOf(strType), str);
                }
                if(connected)
                        peerDisconnect();
                }catch(SocketException se) {
                        if(connected)
                                connectionBreak();
                }catch(IOException ioe) {
                        ioe.printStackTrace();
                }

                closeConnection();
                connectionEnd();
        }
}