Client.java

/**
 * Client program requesting current date from server.
 *
 * Figure 3.27
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts with Java - Eighth Edition
 * Copyright John Wiley & Sons - 2010.
 */
 
import java.net.*;
import java.io.*;

public class DateClient
{
    public static void main(String[] args) throws IOException {
        InputStream clientInput = null;
        OutputStream clientOutput = null;
        BufferedReader bin = null;
        Socket sock = null;
        
        String sendData = "CLIENT: Marco";

        System.out.println("Trying to connect to server " + args[0] + ":" + args[1]);
        try 
        {
            sock = new Socket(args[0],Integer.parseInt(args[1]));
            System.out.println("Socket has been established.");
            
            clientOutput = sock.getOutputStream();            
            PrintWriter pout = new PrintWriter(clientOutput, true);
            pout.println(sendData);                
            

            System.out.println("Waiting for reply...");
            clientInput = sock.getInputStream();
            String replyMessage = "";
            int replyCode = clientInput.read();
            while(replyCode > 10)
            {
                replyMessage += (char) replyCode;
                replyCode = clientInput.read();
            }
            System.out.println("Server replied with: " + replyMessage);
            sock.close();
        }
    
            
        catch (IOException ioe) {
                System.err.println(ioe);
        }
        finally {
            sock.close();
        }
    }
}

Server

/**
 * Time-of-day server listening to port 6013.
 *
 * Figure 3.26
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts with Java - Eighth Edition
 * Copyright John Wiley & Sons - 2010.
 */ 

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

public class DateServer
{
    public static void main(String[] args) {
            
        InputStream serverInputStream = null;
        BufferedReader bin = null;
            
        System.out.println("Trying on port " + args[0]);
        try 
        {
            ServerSocket sock = new ServerSocket(Integer.parseInt(args[0]));
            System.out.println("Server is up ...");

            // now listen for connections
            System.out.println("Server is listening ...");
            Socket client = sock.accept();
            System.out.println("Client socket has been established.");
            // we have a connection     
            
            while(!client.isClosed())
            {
                System.out.println("Connected to " + client.getInetAddress());
                String clientReply = "";
                serverInputStream = client.getInputStream();    
                int streamReturn = serverInputStream.read();
                while(streamReturn > 10)        // read() should return -1 at EOF but returns 10, I can not explain this behavior.
                {
                    clientReply += (char) streamReturn;
                    streamReturn = serverInputStream.read();
                }                    
                System.out.println(clientReply);               
                System.out.println("No more data from input");
                
                System.out.println("Trying to send to client...");                
                PrintWriter pout = new PrintWriter(client.getOutputStream(), true);
                pout.println(clientReply);
                System.out.println("Replied to sender");
                client.close();
                // Server closes the connection it makes to the client
            }            
        }
        catch (IOException ioe) {
                System.err.println(ioe);
        }
    }
}