How to transfer a file from client to server

I need a simple way to transfer a tiny text file from a client java class to a server java class.

If possible, I want to do this bit per bit or octet per octet.

For the little background, this is for a course about java and networks... I am supposed to make java code to transfer the text file, then implement data verification later. (make sure no bits were lost in the way, and use a checksum to verify the data.)

But for now I only need help with file transfer.  Here is my "server" code so far :

// tcpServer.java by fpont 3/2000
 
// usage : java tcpServer <port number>.
// default port is 1500.
// connection to be closed by client.
// this server handles only 1 connection.
 
import java.net.*;
import java.io.*;
 
public class Serveur {
    
    public static void main(String args[]) {
	
	int port;
	ServerSocket server_socket;
	BufferedReader input;
	
	try { 
	    port = Integer.parseInt(args[0]);
	}
	catch (Exception e) {
	    System.out.println("port = 1500 (default)");
	    port = 1500;
	}
 
	try {
	    
	    server_socket = new ServerSocket(port);
	    System.out.println("Server waiting for client on port " + 
			       server_socket.getLocalPort());
	    
	    // server infinite loop
	    while(true) {
		Socket socket = server_socket.accept();
		System.out.println("New connection accepted " +
				   socket.getInetAddress() +
				   ":" + socket.getPort());
		input = new BufferedReader(new InputStreamReader(socket.getInputStream())); 
		// print received data 
		try {
		    while(true) {
			String message = input.readLine();
			if (message==null) break;
			System.out.println(message);
		    }
		}
		catch (IOException e) {
		    System.out.println(e);
		}
		
		// connection closed by client
		try {
		    socket.close();
		    System.out.println("Connection closed by client");
		}
		catch (IOException e) {
		    System.out.println(e);
		}
		
	    }
	    
	    
	}
	
	catch (IOException e) {
	    System.out.println(e);
	}
    }
}
 
 
 
/*import java.io.*;
import java.net.*;
 
public class Serveur {
   static final int port = 1500;
 
   public static void main(String[] args) throws Exception {
        ServerSocket s = new ServerSocket(port);
        Socket soc = s.accept();
 
        // Un BufferedReader permet de lire par ligne.
        BufferedReader plec = new BufferedReader(
                               new InputStreamReader(soc.getInputStream())
                              );
 
        // Un PrintWriter possède toutes les opérations print classiques.
        // En mode auto-flush, le tampon est vidé (flush) à l'appel de println.
        PrintWriter pred = new PrintWriter(
                             new BufferedWriter(
                                new OutputStreamWriter(soc.getOutputStream())), 
                             true);
 
        while (true) {
           String str = plec.readLine();          // lecture du message
           if (str.equals("END")) break;
           System.out.println("ECHO = " + str);   // trace locale
           pred.println(str);                     // renvoi d'un écho
        }
        plec.close();
        pred.close();
        soc.close();
   }
}*/

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