tcp checksum calculation code example

Example: tcp checksum calculation java code

// Java code for Checksum_Sender 
package checksum_sender; 
  
import java.io.*; 
import java.net.*; 
import java.util.*; 
  
public class Checksum_Sender  
{ 
    // Setting maximum data length 
    private int MAX = 100; 
      
    // initialize socket and I/O streams 
    private Socket socket = null; 
    private ServerSocket servsock = null; 
    private DataInputStream dis = null; 
    private DataOutputStream dos = null; 
      
    public Checksum_Sender(int port) throws IOException 
    { 
        servsock = new ServerSocket(port); 
          
        // Used to block until a client connects to the server 
        socket = servsock.accept(); 
          
        dis = new DataInputStream(socket.getInputStream()); 
        dos = new DataOutputStream(socket.getOutputStream()); 
          
        while (true)  
        { 
            int i, l, sum = 0, nob; 
            Scanner sc = new Scanner(System.in); 
            System.out.println("Enter data length"); 
            l = sc.nextInt(); 
              
            // Array to hold the data being entered 
            int data[] = new int[MAX]; 
              
            // Array to hold the complement of each data 
            int c_data[] = new int[MAX]; 
              
            System.out.println("Enter data to send"); 
              
            for (i = 0; i < l; i++)  
            { 
                data[i] = sc.nextInt(); 
                  
                // Complementing the entered data 
                // Here we find the number of bits required to represent 
                // the data, like say 8 requires 1000, i.e 4 bits 
                nob = (int)(Math.floor(Math.log(data[i]) / Math.log(2))) + 1; 
                  
                // Here we do a XOR of the data with the number 2^n -1, 
                // where n is the nob calculated in previous step 
                c_data[i] = ((1 << nob) - 1) ^ data[i]; 
                  
                // Adding the complemented data and storing in sum 
                sum += c_data[i]; 
            } 
              
            // The sum(i.e checksum) is also sent along with the data 
            data[i] = sum; 
            l += 1; 
              
            System.out.println("Checksum Calculated is : " + sum); 
            System.out.println("Data being sent along with Checkum....."); 
              
            // Sends the data length to receiver 
            dos.writeInt(l); 
              
            // Sends the data one by one to receiver 
            for (int j = 0; j < l; j++) 
                dos.writeInt(data[j]); 
              
            // Displaying appropriate message depending on feedback received 
            if (dis.readUTF().equals("success"))  
            {    
                System.out.println("Thanks for the feedback!! Message received  
                                   Successfully!"); 
                break; 
            } 
              
            else if (dis.readUTF().equals("failure"))  
            { 
                System.out.println("Message was not received successfully!"); 
                break; 
            } 
        } 
          
        // Closing all connections 
        dis.close(); 
        dos.close(); 
        socket.close(); 
    } 
  
    // Driver Method 
    public static void main(String args[]) throws IOException 
    { 
        Checksum_Sender cs = new Checksum_Sender(45678); 
    } 
}