// 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);

}