UDP

Question 1

What is UDP?

Answer 1

UDP (User Datagram Protocol) is a connectionless transport-layer protocol for lightweight and fast communication over IP networks, offering no reliability or order guarantees.

Question 2

What are the key features of UDP?

Answer 2

Connectionless Service: No connection setup or teardown; direct communication.
Best-Effort Delivery: No built-in error recovery; packets may be lost, duplicated, or arrive out of order.
Supports multicast messaging.

Question 3

What are common applications of UDP?

Answer 3

Instant Messaging: e.g., ICQ.
Multicast Messaging: Efficient for multiple receivers.
Low-Latency Communication: e.g., Voice-over-IP (VoIP), streaming, and gaming.

Question 4

What is the structure of a UDP datagram?

Answer 4

1.Header (8 bytes):
*Source Port (2 bytes).
*Destination Port (2 bytes).
*Length (2 bytes): Total datagram length.
*Checksum (2 bytes): For error-checking.
2.Data: Variable-size payload with the application message.

Question 5

What is the purpose of ports in UDP?

Answer 5

Ports: Logical endpoints for communication.
Allow multiple applications to use the same network connection.
Examples of well-known ports:
*Port 25: SMTP (Email).
*Port 80: HTTP (Web).
*Port 90: SHTTP (Secure Web).

Question 6

How is UDP encapsulated?

Answer 6

UDP datagrams are encapsulated in IP datagrams, with the following hierarchy:

Frame Header (network-specific).
IP Header (internet addressing).
UDP Header (port and checksum data).
User Data (application message).

Question 7

What are the advantages and limitations of UDP?

Answer 7

Advantages:
*Minimal overhead.
*Fast and suitable for real-time applications.
Limitations:
*No reliability, retransmission, or acknowledgment.
*Applications must manage reliability and data ordering.

Question 8

Provide an example of sending and receiving data using UDP in Java.

Answer 8

Sending Data: DatagramSocket socket = new
DatagramSocket(16789);
String msg = “hello”;
String IP = “229.201.35.83”;
InetAddress address = InetAddress.getByName(IP);
DatagramPacket outputPacket = new
DatagramPacket(msg.getBytes(), msg.length(), address,
12465);
socket.send(outputPacket);

Receiving Data: DatagramSocket socket = new
DatagramSocket(16789);
byte[] data = new byte[256];
DatagramPacket inputPacket = new DatagramPacket(data, 256);
socket.receive(inputPacket);