Explain about UDP in Socket Programming landscape.

1. CHAPTER 3 :
User Datagram Protocol (UDP)
By :
Mr. Asyran Zarizi Bin Abdullah

2. User Datagram Protocol
• It’s a connection-less oriented protocol
• Simpler and less overhead compared to TCP
• Two important classes provided by Java API
under java.net
– DatagramSocket
• Class that support data transmission between sender
and receiver
– DatagramPacket
• Class that support data packet formation

3. Layman Terms for UDP

4. Java.net API
• Socket in JAVA will divide by 3 type :
– Socket client for TCP (stream)
• Java.net.Socket
– Socket server for TCP (stream)
• Java.net.ServerSocket
– Socket server for UDP
• Java.net.DatagramSocket

5. java.net.DatagramSocket class
• Class that use to send and receive DatagramPacket
from or to network
• Datagram is an information but no guarantee of its
content, arrival queue and arrival time.
Constructor
1) DatagramSocket (int port)
2) DatagramSocket(int port, InetAddress inet)
3) DatagramSocket()
Sample Syntax

6. java.net.DatagramPacket class
• Class use to represent a packet information (array
byte)
• Message that can be sent or received and can
arrived in any order.
Constructor
1) DatagramPacket(byte[], buf, int length)
2) DatagramPacket(byte[] buf, int length, InetAddress
address, int port)
Sample Syntax

7. Methods
• getData() : use to take an data information
• getLenght() : use to take datagram length
• getAddress() : use to take ip address information
• getPort() : use to take port address information
• Send(DatagramPacket data) : to send
DatagramPacket to host and port destination
• Receive(DatagramPacket data) : to block
execution until receive 1 complete packet

8. UDP Socket Structure
Did you remember
About previous lab (MySend)
And (MyReceiver)?

9. Example :

10. UDP vs TCP
User Datagram Protocol (UDP) Transmission Control Protocol (TCP)
Connectionless Oriented Connection-Oriented
Provide datagram services Provide stream services
No flow control, sequencing, and
error recovery.
Handles flow control, sequencing,
and error recovery.
Handles designation among
processes in the same host by means
of service port numbers.
Handles designation among
processes in the same host by means
of service port numbers.
There is a comparison between UDP and TCP

11. Datagram Socket
SERVER
1. Create a DatagramSocket object
– DatagramSocket dgramSocket = new
DatagramSocket(1234);
2. Create a buffer for incoming datagrams
– byte[] buffer = new byte[256];
3. Create a DatagramPacket object for the incoming
datagram
– DatagramPacket inPacket = new
DatagramPacket(buffer,buffer.length);
4. Accept an incoming datagram
– dgramSocket.receive(inPacket)

12. Datagram Socket
SERVER
5. Accept the sender’s address and port from the packet
– InetAddress clientAddress = inPacket.getAddress();
– int clientPort = inPacket.getPort();
6. Retrieve the data from the buffer
– string message = new String(inPacket.getData(), 0,
inPacket.getLength());
7. Create the response datagram
– DatagramPacket outPacket = new
DatagramPacket(response.getBytes()
, response.length(), clientAddress, clientPort);
8. Send the response datagram
– dgramSocket.send(outPacket)
9. Close the DatagramSocket: dgram.close();

13. Datagram Packet
CLIENT
1. Create a DatagramSocket object
– DatagramSocket dgramSocket = new
DatagramSocket;
2. Create the outgoing datagram
– DatagramPacket outPacket = new
DatagramPacket(message.getBytes(),
message.length(),host, port);
3. Send the datagram message
– dgramSocket.send(outPacket)
4. Create a buffer for incoming datagrams
– byte[] buffer = new byte[256];

14. Datagram Packet
CLIENT
5. Create a DatagramPacket object for the incoming
datagram
– DatagramPacket inPacket = new DatagramPacket(buffer,
buffer.length);
6. Accept an incoming datagram
– dgramSocket.receive(inPacket)
7. Retrieve the data from the buffer
– string response = new String(inPacket.getData(), 0,
inPacket.getLength());
8. Close the DatagramSocket:
– dgram.close();

15. MulticastSocket
• A class that use connection-less oriented
protocol to connect multiple network device
to form a group.
• Data, File or any media can be send by 1 party
to be received by multiple recipient.

16. MulticastSocket

17. Multicast Socket
• MulticastSocket class is a subclass from
DatagramSocket
– public class MulticastSocket extends DatagramSocket
• Calling class without parameter
– public MulticastSocket() throws SocketException
• Calling class with parameter port
– public MulticastSocket(int port) throws SocketException
• Calling class with parameter SocketAddress
– public MulticastSocket(SocketAddress bindAddress) throws
IOException

18. Multicast Socket
• Uses existing DatagramPacket object to form
the data need to be transmit
• MulticastSocket object is created on the
server or receiver side
– Example
• Later the object is bind to the server IP as
central grouping point
– Example