Applications using TCP and UDP Sockets like DNS, SNMP and File Transfer

Aim

To write a java program for DNS application

Algorithm

1.Start the program.

2.Get the frame size from the user

3.To create the frame based on the user request. 4.To send frames to server from the client side.

5.If your frames reach the server it will send ACK signal to client otherwise it will send NACK signal to client.

6.Stop the program

Program

/ UDP DNS Server Udpdnsserver

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

public class udpdnsserver

{

private static int indexOf(String[] array, String str)

{

str = str.trim();

for (int i=0; i < array.length; i++)

{

if (array[i].equals(str)) return i;

}

return -1;

}

public static void main(String arg[])throws IOException

{

String[] hosts = {"yahoo.com", "gmail.com","cricinfo.com", "facebook.com"};

String[] ip = {"68.180.206.184", "209.85.148.19","80.168.92.140", "69.63.189.16"};

System.out.println("Press Ctrl + C to Quit");

while (true)

{

DatagramSocket serversocket=new DatagramSocket(1362); byte[] senddata = new byte[1021];

byte[] receivedata = new byte[1021];

DatagramPacket recvpack = new DatagramPacket(receivedata, receivedata.length);

serversocket.receive(recvpack);

String sen = new String(recvpack.getData()); InetAddress ipaddress = recvpack.getAddress(); int port = recvpack.getPort();

String capsent;

System.out.println("Request for host " + sen);

if(indexOf (hosts, sen) != -1) capsent = ip[indexOf (hosts, sen)]; else capsent = "Host Not Found"; senddata = capsent.getBytes();

DatagramPacket pack = new DatagramPacket (senddata, senddata.length,ipaddress,port); serversocket.send(pack);

serversocket.close();

}

}

}

//UDP DNS Client –

Udpdnsclient

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

public class udpdnsclient

{

public static void main(String args[])throws IOException

{

BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); DatagramSocket clientsocket = new DatagramSocket();

InetAddress ipaddress; if (args.length == 0)

ipaddress = InetAddress.getLocalHost(); else

ipaddress = InetAddress.getByName(args[0]); byte[] senddata = new byte[1024];

byte[] receivedata = new byte[1024];

int portaddr = 1362;

System.out.print("Enter the hostname : ");

String sentence = br.readLine();

Senddata = sentence.getBytes();

DatagramPacket pack = new DatagramPacket(senddata,senddata.length, ipaddress,portaddr);

clientsocket.send(pack);

DatagramPacket recvpack =new DatagramPacket(receivedata,receivedata.length);

clientsocket.receive(recvpack);

String modified = new String(recvpack.getData()); System.out.println("IP Address: " + modified); clientsocket.close();

}

}

OUTPUT Server

javac udpdnsserver.java

java udpdnsserver

Press Ctrl + C to Quit Request for host yahoo.com

Request for host cricinfo.com

Request for host youtube.com

Client

javac udpdnsclient.java

java udpdnsclient

Enter the hostname : yahoo.com

IP Address: 68.180.206.184

java udpdnsclient

Enter the hostname : cricinfo.com

IP Address: 80.168.92.140

java udpdnsclient

Enter the hostname : youtube.com

IP Address: Host Not Found