#2 (UDP)

Distributed Systems
Lecture -2-
Created by :
Eng. Ghadeer Al Hasan
UDP

Intro 1
- DatagramSockets are Java’s mechanismfor network communication via UDP insteadof
TCP.
- Java provides DatagramSocket to communicate over UDP insteadof TCP.
- DatagramSockets can be usedto both send and receive packets over the Internet.

Intro… 2
- It is preferredover TCP is the live coverage of TV channels.
- In this aspect, we want to transmit as many frames to live audience as possible not worrying about
the loss of one or two frames.(TCP being a reliable protocol add its own overhead while transmission)
- Another example where UDP is preferred is online multiplayer gaming.
- In games likecounter-strike or call of duty, it is not necessaryto relayall the information but the
mostimportant ones.
- It should also be noted that most of the applications in real life uses careful blendof both UDP and
TCP; transmitting the critical data over TCP and rest of the data via UDP.

Java Datagram programming model Steps

1st Step 4
1- Creation of DatagramSocket: - First, a datagramSocket object is createdto carry the
packet to the destination and to receive it whenever the server sends any data.
To createa datagramSocket followingconstructors can be used:
protected DatagramSocket DatagramSocket()
protected DatagramSocket DatagramSocket(int port)
protected DatagramSocket DatagramSocket(int port, InetAddress inetaddress)
What is
port?

2nd Step 5
2 - Creation of DatagramPacket: In this step, the packet for sending/receiving data via a
datagramSocket is created.
Constructor to senddata:
DatagramPacket(byte buf[], int length, InetAddress inetaddress, int port)
Parameters:
buf - the packet data.
offset - the packet data offset.
length - the packet data length.
address - the destination socket address.
Constructs a DatagramPacket for sending data at specifiedaddress and specifiedport.

2nd Step… 6
Constructor to receive the data:
DatagramPacket(byte buf[], int length)
Parameters:
buf - thepacket data.
length- the packet data length.
Constructs a DatagramPacket for receiving the data of lengthlengthin the byte array buf.

3rd Step 7
Invoke a send() or receive() call on socket object
void send(DatagramPacket packet)
void receive(DatagramPacket packet)

9DatagramSocket socket = null;
byte[] receiverBuffer = null;
DatagramPacket receivePacket = null;
private void initializeVarible(){
try {
socket = new DatagramSocket(Constants.PORT);
receiverBuffer = new byte[Constants.BUFFER_SIZE];
} catch (SocketException ex) {
log("initializeVarible : " + ex.getMessage());
}
}
private String receiveData(){
String line = "";
try {
receivePacket = new
DatagramPacket(receiverBuffer,receiverBuffer.length);
socket.receive(receivePacket);
line = new
String(receivePacket.getData(),0,receivePacket.getLength());
} catch (IOException ex) {
log("receiveData : " + ex.getMessage());
}
return line;
}

10
public static void main(String[] args){
Server server = new Server();
server.initializeVarible();
server.connecting();
}
private void connecting(){
while(true){
String data = receiveData();
log("Client : " + data);
if(data.equals(Constants.STOP)){
log("Client say bye...Exiting");
break;
}
receiverBuffer = new byte[Constants.BUFFER_SIZE];
}
}

12Scanner scan = null;
DatagramSocket socket = null;
byte[] buffer = null;
private void initializeVarible(){
try {
scan = new Scanner(System.in);
socket = new DatagramSocket();
}
}
private void send(String message){
try {
InetAddress ip = InetAddress.getLocalHost();
buffer = message.getBytes();
DatagramPacket packetSend = new
DatagramPacket(buffer,buffer.length,ip,Constants.PORT);
socket.send(packetSend);
log("send : " + ex.getMessage());
}
}

13
while(true){
String line = readFromKeyboard();
send(line);
if(line.equals(Constants.STOP)){
break;
}
}
}
private String readFromKeyboard(){
String line = scan.nextLine();
return line;
}
Client client = new Client();
client.initializeVarible();
client.connecting();
}

Server Side 16
MulticastSocket socket = null;
DatagramPacket receivePacket = null;
Scanner scan = null;
private void initializeVarible() {
try {
socket = new MulticastSocket();
buffer = new byte[Constants.BUFFER_SIZE];
scan = new Scanner(System.in);
log("Server Running...");
}
}

Server Side… 17
private String readFromKeyboard(){
String line = scan.nextLine();
return line;
}
private void send(String message) {
try {
InetAddress ip = InetAddress.getByName(Constants.IP);
buffer = message.getBytes();
DatagramPacket packetSend = new DatagramPacket(buffer, buffer.length,
ip, Constants.PORT);
socket.send(packetSend);
log("Message Sent");
log("send : " + ex.getMessage());
}
}

Server Side… 18
private void connecting() {
while (true) {
String data = readFromKeyboard();
send(data);
}
}
public static void main(String[] args) {
Server server = new Server();
server.initializeVarible();
server.connecting();
}

Client Side 19
MulticastSocket socket = null;
DatagramPacket packet = null;
InetAddress ip = null;
private void initializeVarible() {
try {
socket = new MulticastSocket(Constants.PORT);
ip = InetAddress.getByName(Constants.IP);
}
}

Client Side… 20
private String receiveData() {
String line = "";
try {
packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
line = new String(packet.getData(), 0, packet.getLength());
log("receiveData : " + ex.getMessage());
}
return line;
}
private void joinGroup(){
try {
socket.joinGroup(ip);
log("Client Running...");
log("joinGroup : " + ex.getMessage());
}
}

Client Side… 21
joinGroup();
while(true){
String line = receiveData();
log("Client Received : " + line);
}
}
Client client = new Client();
client.initializeVarible();
client.connecting();
}

References 24
- YouTube link
https://www.youtube.com/playlist?list=PLtDIUAtyP4lhV7CsYfLuIx26UeG4J-ujZ
- GitHub
https://github.com/Ghadeerof

#2 (UDP)

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