Question

I would like to take text from a file and then send it to the server for it to capitalise before sending back to the client where it is printed out. How do I achieve this?

I can read one line and send that back to the client and I’ve managed to write multiple lines to the output stream (for the server to read) but I don’t know what to do now..

I have a client that reads text from a file:

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

public class Client 
{
    public static void main(String[] args)
    {
        try
        {
            // First create the input from keyboard
            BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Client Program");

            // Next we need to find out the IP address and port number of the server
            System.out.print("Enter IP Address of server: ");
            String ip = input.readLine();
            System.out.print("Enter port number of server: ");
            String port_string = input.readLine();

            // The port number needs to be an int, so convert the string to an int
            int port = Integer.parseInt(port_string);

            // Connect to the server
            Socket sock = new Socket(ip, port);


            // Create the incoming stream to read messages from
            DataInputStream network = new DataInputStream(sock.getInputStream());

            //Create the output stream to the client
            DataOutputStream message = new DataOutputStream(sock.getOutputStream());

            //Send message
            //message.writeUTF("some text");
            FileReader file = new FileReader("text.dat");
            BufferedReader input_file = new BufferedReader(file);

            // Loop until EOF
            while (input_file.ready()){
            // Read next line from the file
                String line = input_file.readLine();
                // Write line to server
                message.writeUTF(line + "\n");
                //System.out.println(line);
            }

            // Display our address
            System.out.println("Address: " + sock.getInetAddress());
            String line;

            // Loop until the connection closes, reading from the network
            while ((line = network.readUTF()) != null)
            {
                // Display the received message
                System.out.println(line);
            }
        }
        catch (IOException ioe)
        {
            // This is expected when the server closes the network connection
            System.err.println("Error in I/O");
            System.err.println(ioe.getMessage());
            System.exit(-1);
        }
    }
}

And then a server that is supposed to take those strings and capitalise them:

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

public class Server 
{
    public static void main(String[] args)
    {
        try
        {
            // First create the input from the keyboard
            BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Server Program");

            // Get the port to listen on
            System.out.print("Enter port number to listen on: ");
            String port_string = input.readLine();

            // The port number needs to be an int, so convert the String to an int
            int port = Integer.parseInt(port_string);

            // Create a ServerSocket to listen on this address
            ServerSocket server = new ServerSocket(port);

            // Accept an incoming client connection on the server socket
            Socket sock = server.accept();

            // Create the output stream to the client
            DataOutputStream network = new DataOutputStream(sock.getOutputStream());

            //Create the incoming stream to read messages from
            DataInputStream message =  new DataInputStream(sock.getInputStream());



            String newLine = inFromClient.readLine();

            //Line to read
            String line;
            line = message.readUTF();
            line = line.toUpperCase();




            // Send message
            network.writeUTF(newLine);

            // Close sockets.  This will cause the client to exit
            sock.close();
            server.close();
        }
        catch (IOException ioe)
        {
            System.err.println("Error in I/O");
            System.err.println(ioe.getMessage());
            System.exit(-1);
        }
    }
}

Answer 1

The problem is your server is reading the stream only once and closing the socket connection.
How will your server know you have finished sending the client data to the server socket ?
You should modify the server to listen to the port till you have finished sending the whole text. For that do something like –

String newLine;
while ( true )
newLine = inFromClient.readLine();              
          if (newLine.equalsIgnoreCase("END"))
{
    break;
}

          newLine = newLine.toUpperCase();                 

// Send message             
          network.writeUTF(newLine);
}
// Close sockets.  This will cause the client to exit

sock.close();               
server.close();

And from the client send “END” after all lines have been sent.