Session04-NP With Socket and Datagram

8/3/2019 Session04-NP With Socket and Datagram

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1

Session 4. Network programming

with socket and datagram Socket

InetAddress

TCP socket

UDP socket (Datagram)

Case study 3



2

What is a socket? Original idea came from UNIX

“The network is just like a file system”

Read and write a stream of data “to thenetwork” through socket

A socket is bound to a port number so that

the TCP layer can identify the correct

application for the data



3

Introduction to Sockets Why Sockets?

Used for Interprocess communication.

The Client-Server model

Most interprocess communication uses client-server

model

Client & Server are two processes that wants to

communicate with each other The Client process connects to the Server process, to

make a request for information/services own by the

Server.



4

Once the connection is established between

Client process and Server process, they can start

sending / receiving information.

What are Sockets?

End-point of interprocess communication.

An interface through which processes can send /

receive information



5

Port



6

Communication between

processes : using port and socket

message

agreed port any port

socket socket

Internet address = 138.37.88.249 Internet address = 138.37.94.248

other ports client server

• Port: The destination of a message• Socket: The final point for processes communication• Each socket is associated with UDP or TCP



7

Port



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Local socket address: Local IP address and port

number Computer’s address likes IP address, example:

203.162.36.149 mapping with www.cit.ctu.edu.vn



9

The InetAddress class The java.net.InetAddress class is used to

represent an IP address as an object. It is

also used to resolve from host name to IPaddress and vice versa.

No Constructors, instead, factory methods

are provided.



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Static InetAddress

getByName(String host)

Takes a hostname and returnsInetAddress object representing

its IP address. Static InetAddress[]

getAllByName(String

host)

Takes a hostname and returnsan array of InetAddress objectsrepresenting its IP addresses.

static InetAddress

getLocalHost()

Returns an InetAddress objectrepresenting the IP address of the local host

String getHostAddress() Returns IP address string of thisInetAddress object

string getHostName() Returns the hostname of thisInetAddress object.



11

public class IPAddress {

public static void main(String[] agrs){try {

InetAddress local = InetAddress.getLocalHost();

InetAddress[] addresses =

InetAddress.getAllByName(local.getHostName());System.out.println("My Address is: "+local);

System.out.println("My Host name is: "+local.getHostName());

System.out.println("My IP Address is: "+local.getHostAddress());

for(int i=0;i<addresses.length;i++){System.out.println(addresses[i]);

} } catch (UnknownHostException ex) {

System.out.println("Exception :"+ex);

} }}

IPAddress.java



12

TCP Sockets (Stream Sockets) Java provides two classes for creating TCP

sockets: Socket and ServerSocket.

The ServerSocket class is used to by serverto accept client connections.The

constructors for the class are:

public ServerSocket(int port) public ServerSocket(int port, int backlog)

public ServerSocket(int port, int backlog,

InetAddress networkInterface)



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This class is used by clients to make a

connection with a server

Socket constructors are: Socket(String hostname, int port)

Socket(InetAddress addr, int port)

Socket(String hostname, int port, InetAddress localAddr, int localPort)

Socket(InetAddress addr, int port, InetAddress

localAddr, int localPort)



14

Algorithm for TCP server Find the IP address and port number of server

Create a TCP server socket

Bind the server socket to server IP and Port number

(this is the port to which clients will connect)

Accept a new connection from client

returns a client socket that represents the client

which is connected Send/ receive data with client using the client socket

Close the connection with client



15

Algorithm for TCP client Find the IP address and port number of server

Create a TCP socket

Connect the socket to server (Server must be

up and listening for new requests)

Send/ receive data with server using the

socket

Close the connection



16

The socket APIs for connection-oriented protocol (TCP)



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Reading from/ Writing to a

Socket

var1

var2

Socket

InputStream

OutputStream



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On the TCP server side ServerSocket objects use their accept() method to

connect to a client

public Socket accept()

accept() method returns a Socket object, and its

getInputStream() and getOutputStream()

methods provide streams for reading and writing

to the client. There are no getInputStream() or

getOutputStream() methods for ServerSocket



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Reader/Writer

BufferedReader reader=null;

PrintWriter writer=null;

reader=new BufferedReader(new

InputStreamReader(client.getInputStream()));

writer.println("Welcome to my server!!");

writer=new PrintWriter(client.getOutputStream(), true);

String msg=reader.readLine();

DataInputStream reader=null;

DataOutputStream writer=null;

reader = new DataInputStream(client.getInputStream());

writer=new DataOutputStream(client.getOutputStream());

writer.writeUTF(msg);



20

Close:

writer.close();

reader.close();

client.close();

server.close();



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public class TcpEchoServer {

public static void main(String[] agrs) throws IOException{

ServerSocket server=null;

Socket client=null;



int port=1234;

try {

server = new ServerSocket(port);

System.out.println("Waiting connection...");

client=server.accept();

} catch (IOException ex) {

System.err.println("Could not listen on port "+port);

System.exit(1);

}

TcpEchoServer.java



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writer=new PrintWriter(client.getOutputStream(), true);

writer.println("Welcome to my server!!");

String msg;

while((msg = reader.readLine())!= null){

System.out.println("Message from client: "+msg);writer.println(msg);

if(msg.equals("Bye!"))

break;

}writer.close(); reader.close();

client.close(); server.close();

}}



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On the TCP client side Data is sent and received with output and input

streams.

The Socket class has the following methods, that

retruns InputStream and the OutputStream for

reading and writing to the socket

public InputStream getInputStream()

public OutputStream getOutputStream() There's also a method to close a socket:

public synchronized void close()

T E h Cli t j



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public class TcpEchoClient {

public static void main(String[] agrs) throws IOException{

Socket client=null;BufferedReader reader=null;


BufferedReader in=null; int port=1234;

try {client = new Socket("localhost", port);



writer=new PrintWriter(client.getOutputStream(), true);} catch (UnknownHostException ex) {

System.err.print(ex); System.exit(1);


System.err.println(ex); System.exit(1); }

TcpEchoClient.java



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in=new BufferedReader(new InputStreamReader(System.in));

System.out.println(reader.readLine());

String msg;

System.out.print("Enter message :");while((msg=in.readLine()).length()!=0){

writer.println(msg);

System.out.println("message from server:"+reader.readLine());

System.out.print("Enter message :");}

in.close();

writer.close();

reader.close();

client.close();

}

}



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TCP chatting



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chatServer.javaServerSocket server=null;

Socket client=null;



String msg;

private void btSendActionPerformed(java.awt.event.ActionEventevt) {

String s=message.getText();

room.append("Server: "+s+"\n");

writer.println(s);message.setText("");

}



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public void listenSocket() {

try {

server = new ServerSocket(1234);


System.out.println("Could not listen on port 1234");

System.exit(1);

}try{

client = server.accept();


System.out.println("Accept failed : 1234");

System.exit(1);

}



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try{



writer=new PrintWriter(client.getOutputStream(),true);}catch(IOException e){

System.out.print("Accept failed: 1234");

System.exit(1);}

while(true){try{

msg = reader.readLine();

room.append("client:"+msg+"\n");

} catch (IOException ex) {System.out.println("Read fialed");

System.exit(1);

}}}



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protected void finalize(){

//Clean up

try{

reader.close();

writer.close();

server.close();

} catch (IOException e) {

System.out.println("Could not close.");

System.exit(1);

}

}



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chatClient.javaSocket client=null;

BufferedReader reader=null;PrintWriter writer=null;

String msg;

private void

btSendActionPerformed(java.awt.event.ActionEvent evt) {

String s=message.getText();

room.append("client: "+s+"\n");

writer.println(s);message.setText("");

}



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public void listenSocket(){

try {

client = new Socket("localhost", 1234);

} catch (UnknownHostException ex) {System.out.print("Accept failed: 1234");

System.exit(1);



System.exit(1);

}



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try{



writer=new PrintWriter(client.getOutputStream(),true);

}catch(IOException e){


System.exit(1); }

while(true){

try{

msg = reader.readLine();

room.append("server:"+msg+"\n");


System.out.println("Read fialed");

System.exit(1);

}}



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protected void finalize(){

//Clean up

try{reader.close();

writer.close();

client.close();} catch (IOException e) {

System.out.println("Could not close.");

System.exit(1);}

}



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What are Sockets and Threads? A server program typically provides

resources to a network of client

programs. Client programs send

requests to the server program, andthe server program responds to the

request.

One way to handle requests from more than one client is to

make the server program multi-threaded. A multi-threadedserver creates a thread for each communication it accepts

from a client. A thread is a sequence of instructions that run

independently of the program and of any other threads.



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Creating Threads in Java Runnable interface

Create object implementing Runnable interface Pass it to Thread object via Thread constructor

Example

public class MyT implements Runnable {

public void run() {

… // work for thread

}

}

Thread t = new Thread(new MyT()); // create thread

t.start(); // begin running thread

… // thread executing in parallel



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threadServer.javaclass Clients implements Runnable{

private Socket client;

private JTextArea text;Clients(Socket client, JTextArea text){

this.client=client;

this.text=text;

}

bli id () {



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public void run() {

String message;

BufferedReader read = null;

PrintWriter write = null;

…………………

while(true){

try {

message = read.readLine();

String[] data;

data=message.split("-");

//Send data back to client

write.println("Server "+data[1]);

text.append(data[0]+" "+data[1]+"\n");


System.out.print("read failed");

System.exit(-1);

} }



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public class threadServer extends javax.swing.JFrame {

ServerSocket server;

private void listenSocket(){

server = new ServerSocket(1234);

……………..

while(true){

Clients c;

………..

c = new Clients(server.accept(), text);

Thread t=new Thread(c);

t.start();

…………….

}



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threadClient.javaSocket client;

BufferedReader read=null;

PrintWriter write=null;

static String name=null;

/** Creates new form threadClient */

public threadClient() {

initComponents();name=JOptionPane.showInputDialog("Enter your name:");

txt.requestFocus();

}



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public void listenSocket(){

……………

client = new Socket("localhost", 1234);

read=new BufferedReader(new


write=new PrintWriter(client.getOutputStream(),true);

…………………….}



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private void

jButton1ActionPerformed(java.awt.event.ActionEvent evt)

{

String s=txt.getText();write.println(name+"-"+s);

text.append(name +" "+s+"\n");

txt.setText("");

//Receive text from server

try {

String ss = read.readLine();

text.append(ss+"\n");


System.out.print("read error");

System.exit(-1);

}}



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UDP Sockets (Datagram Sockets) Packet is a block of data with length that can vary between

successive packets, ranging from 7 to 65,542 bytes, including

the packet header. Packets may travel along different paths

depending on the state of the network.

A datagram is an independent, self-contained message sent

over the network whose arrival, arrival time, and content are

not guaranteed.

Each packet has a time-to-live (TTL) counter, which is

updated when it is routed along to the next point in the

network. When the timer expires, it will be discarded, and

the recipient will not be notified.



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Java Support for UDP Java provides two classes for creating UDP

Sockets:

DatagramPacket class, used to represent

the data for sending and receiving.

DatagramSocket class for creating a

socket used to send and receive

DatagramPackets.



45

DatagramPacket Class

A DatagramPacket object represents adata packet intended for transmission usingUDP.

It contains addressing information such asan IP address and a port.

When a DatagramPacket is read from a

UDP socket, the IP address/port of thepacket represents the address/port of thesender.



46

When a DatagramPacket is used to send a

UDP packet, the IP address/port represents theaddress/port of the recipient.

DatagramPacket

IP address (java.net.InetAddr)

Port address (int)

Packet data (byte[])



47

Creating a DatagramPacket

Constructor to use for creating aDatagramPacket for receiving incoming

UDP packets:DatagramPacket(byte[] buffer, int

length)

Example:byte b[]=new byte[1024];

DatagramPacket packet;

packet = new DatagramPacket(b, b.length);



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Constructor for sending :public DatagramPacket(byte[] data, int

length, InetAddress addr, int port)



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String s=”This is an example of UDP Programming”;

byte[] b= s.getBytes();

try{

InetAddress name=InetAddress.getByName(“www.vnn.vn”);

int port =1234;

DatagramPacket dataSend=new

DatagramPacket(b,b.length,name,port); //sending a packet

}

catch(IOException e){

System.err.println(e);

}



50

DatagramPacket Methods

InetAddress getAddress()

byte[] getData()

int getLength() int getPort()

void setAddress(InetAddress addr)

void setData(byte[] buffer) void setLength(int length)

void setPort(int port)



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Creating a DatagramSocket

Constructor to use for creating a clientDatagramSocket:

DatagramSocket() throwsjava.net.SocketException

Example:DatagramSocket socket;

try {socket = new DatagramSocket();

} catch (SocketException exception) {

…}



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Constructor to use for creating a server

DatagramSocket:DatagramSocket(int port) throws

java.net.SocketException

Example:DatagramSocket socket;

try {

socket = new DatagramSocket(2000);

} catch (SocketException exception) {

…

}



53

DatagramSocket Methods void close()

void connect(InetAddress r_addr, int r_port)

void disconnect()

InetAddress getInetAddress()

int getPort()

InetAddress getLocalAddress()

int getLocalPort()

int getReceiveBufferSize() throws




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int getSendBufferSize() throws java.net.SocketException

int getSoTimeout() throws

java.net.SocketException void receive(DatagramPacket packet) throws

java.io.IOException

void send(DatagramPacket packet) throws

java.io.IOException

int setReceiveBufferSize(int length) throws


int setSendBufferSize(int length) throws java.net.SocketException

void setSoTimeout(int duration) throws




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UDP Server

Step 1:To open a server socket at port number

specified.

try {DatagramSocket myServer = new

DatagramSocket(port);

}

catch(SocketException e) {

System.out .println(e);

}



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Step 2: Create a packet from the DatagramPacket object to

receive data from the client to process.

try { // reveive

byte[] receiveData = new byte[1024];

DatagramPacket receivePacket = new

DatagramPacket(receiveData, receiveData.length);

myServer.receive(receivePacket);

input = new String( receivePacket.getData());

// process data

}catch (SocketException e) {

System.out .println(e);}catch (IOException e) {


}

Step 3:Packing DatagramPacket packet of information and to



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Step 3: ac g atag a ac et pac et o o at o a d to

send it back to the client, respectively.

try { //Packing datagram

InetAddress IPAddress = receivePacket.getAddress();

int port = receivePacket.getPort();

byte[] sendData = (dũ liệu đã xử lí).getBytes();

DatagramPacket sendPacket =

new DatagramPacket(sendData, sendData.length, IPAddress,

port);

// send it back to the client

myServer.send(sendPacket);



}catch (IOException e) {


}



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UDP Client

Step 1: Open a socket client to server name

defined at a port number specified.

try {

mySocket = new DatagramSocket();

} catch (SocketException e) {

System.err .println(e);

}

Step 2: packaging information on DatagramPacket packet



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Step 2: packaging information on DatagramPacket packet

to send.

byte[] sendData = new byte[1024]; // sending data buffer

try {netAddress IPAddress =

InetAddress.getByName("localhost");

sendData = (sending data).getBytes();

DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress,

port);


System.err .println(e);} catch (IOException e) {


}



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Step 3: Send data to the server.

try {

mySocket.send(sendPacket);} catch (SocketException e) {


} catch (IOException e) {System.err .println(e);

}

Step 4: Wait to receive data (already processed)



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Step 4: Wait to receive data (already processed).

byte[] receiveData = new byte[1024];

try {

DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);

mySocket.receive(receivePacket);

receivedData = receivePacket.getData();



} catch (IOException e) {

System.err .println(e);}



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Step 5: Close socket have been created.

try {

mySocket.close();

} catch (Exception e) {


}



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UDPServer.javapublic class UDPServer {

public static final int PORT = 1234;

public static final int BUFSIZE = 256;

DatagramSocket server = null; String input;

public void UDPServer(){

try {

server = new DatagramSocket(PORT);

} catch(SocketException e) {

System.out.println(e);

System.exit(1);

} }

public void listening(){



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public void listening(){

byte[] receiveData = new byte[BUFSIZE];

byte[] sendData = new byte[BUFSIZE];

while(true){

try { // Receive data



try {

server.receive(receivePacket);


}input = new String( receivePacket.getData());

System.out.println(input);

InetAddress IPAddress = receivePacket getAddress();



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InetAddress IPAddress = receivePacket.getAddress();

int port = receivePacket.getPort();

sendData = input.getBytes();

DatagramPacket sendPacket =

new DatagramPacket(sendData, sendData.length,

IPAddress, PORT);

// Gui du lieu ve client

server.send(sendPacket);


System.out.println(e);

}catch (IOException e) {System.out.println(e);

} } }



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UDPClient.javapublic class UDPClient {

public static final int PORT = 1234;

public static final int BUFSIZE = 256;

DatagramSocket client = null;

// Tao ket noi

public void connection(){

try {

client = new DatagramSocket();


System.err.println(e); System.exit(1);

}}

public void send(String str){



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p ( g ){

if (client != null) {

byte[] sendData = new byte[BUFSIZE]; // bo dem gui du

lieutry {

InetAddress IPAddress=null;

try {

IPAddress = InetAddress.getByName("localhost");} catch (UnknownHostException ex) {

}

sendData = str.getBytes();

DatagramPacket sendPacket = newDatagramPacket(sendData, sendData.length, IPAddress, PORT);

client.send(sendPacket);


} catch (IOException e) { }}}

public String receive(){



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public String receive(){

if (client != null) {

byte[] receiveData = new byte[BUFSIZE];

// bo dem nhan du lieutry {



client.receive(receivePacket);return new String(receivePacket.getData());


System.err.println(e);

} catch (IOException e) {System.err.println(e);

} }

return null; }

public static void main(String[] agrs){



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p ( g[] g ){

UDPClient c=new UDPClient();

c.connection();

BufferedReader stdin=new BufferedReader(newInputStreamReader(System.in));

String msg=null;

while(true){

System.out.println("Input sessages: ");try {

msg = stdin.readLine();

} catch (IOException ex) { }

c.send(msg);System.out.println(c.receive());

if(msg.equals("exit"))

break; }

c.close(); }



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Multicast in Java

There are following types of method for

delivering or transmitting data in the

network. Unicast

Multicast

Broadcast



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Unicast

Unicast: This method solves network traffic

problems to deliver messages from one host

to another.



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Multicast

Multicast: In this method, you can transmit

data or messages to all destination host

machines

Broadcast



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Broadcast: It provides better facility to solve a network

traffic problems than unicast. In broadcast, the servergenerates only one data stream but it can be delivered to all

destination host whether interested or not. Here

transmitting data or packets to be received by every host

machine on entire network that means you send data or

messages to multiple host at a time or simultaneously



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Multicast Server in Java when program runs that has two command buttons 'Start' and

'Stop'. First time 'Start' button is enable and another is disable.

When you click 'Start' button, the multicast server functions but

button is disable, and the message "Server is started" is

displayed in text area. If you want to stop the server then click on the 'Stop' button then multicast server resume its function

with a message that "Server is stopped". The multicast server

receives requests or messages from multicast client, which has

the port number '5000' and IP(Internate Protocol) number

('224.0.0.0', '235.0.0.1', '235.255.0.1', '224.0.255.1'). The server

also sends same message to all multicast clients that are

interested for this group otherwise don't perform these works.



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UDP Multicast Client in Java That has four clients identified by the specific

IP('224.0.0.0', '235.0.0.1', '235.255.0.1', '224.0.255.1')

and port number(5000). Those of any client sends and

receives IP packet that depends upon the check box. If check box is enable then send or receive IP packets

otherwise it couldn't be send or receive. Just bellow

provides a text area that can be used for writing the

message and receiving the message to multicastserver. It has also 'Send' command button for sending

IP packet to multicast server.



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Case study 3

5- 6 điểm: làm 2 bài ở mức 1

7- 8 điểm : qua mức 5-6 điểm, làm tiếp bài

ở mức 2

9- 10 điểm: qua mức 5-6 điểm, làm tiếp bàiở mức 3(chỉ cần chọn 1 trong 2 bài) – ưu

tiên bài 2 hơn.

Session04-NP With Socket and Datagram

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