This document discusses socket programming concepts in Java including server-client communication using sockets, the InetAddress class and its methods like getLocalHost(), getByName(), and getAllByName(), and the Socket and ServerSocket classes. It provides code examples to demonstrate how to use these classes and methods to establish connections between a client and server and exchange data over the network.

1. Group Members
Gurpreet Kaur(155)
Himani Kakria
Ritika Sharma
Reetu Rani

2. Contents
O Socket Programming
O Server-Client Communication
O .net Package
O The InetAddress Class & its methods
O getLocalHost()
O getByName(String hostName)
O getAllByName(String hostName)
O getAddress() & getHostName()
O Socket Class
O ServerSocketClass

3. Socket Programming
Networking - process of making two or more computers
communicate.
The important concept associated with networking is the concept of
Sockets and Ports.
SOCKET - A socket is one end-point of a two-way communication link
between two programs running on the network.
Socket classes are used to represent the connection between a client
program and a server program.

4. Server-Client Communication
O Normally, a server has a socket that is bound to a specific port
number.
O On the client-side: The client knows the hostname of the machine
on which the server is running and the port number on which the
server is listening.
O To make a connection request, the client tries to connect with the
server on the server's machine and port.
O If everything goes well, the server accepts the connection.
O On the client side, if the connection is accepted, a socket is
successfully created and the client can use the socket to
communicate with the server.

5. .net Package
O Provide support for networking.
O Contains classes and interfaces to encapsulate the “Socket”
Paradigm.
O The java.net package provides two classes—
O Socket - implement the client side of the connection
O Ser verSocket- implement the server side of the connection

6. The InetAddress Class
O It converts the domain name of Internet address into an
Object. This class represents an Internet Protocol (IP)
address.
O Doesn’t have Constructors.
O Three static methods are used to create instances.
O getLocalHost()
O getByName(String hostName)
O getAllByName(String hostName)
O All these methods throw UnknownHostException if the
method cannot resolve the host name.

7. getLocalHost()
import java.net.*;
class obtainIP
{
public static void main(String args []) throws UnknownHostException
{
InetAddress adr;
adr=InetAddress.getLocalHost();
System.out.println("nInfo about Machine: " + adr);
}
}

8. getByName(String hostName)
import java.io.*;
import java.net.*;
class obtainIP2
{ public static void main(String args []) throws IOException
{ InetAddress adr;
String host;
DataInputStream input=new DataInputStream(System.in);
System.out.println("Enter the Machine's Hostname");
host=input.readLine();
try {
adr=InetAddress.getByName(host);
System.out.println("nInfo about Host "" + host + "" is:- " + adr);
}
catch( UnknownHostException e) {
System.out.println("No such host exist"); }
}
}

9. Output

10. getAllByName(String hostName)
import java.io.*; try {
import java.net.*; adr=InetAddress.getAllByName(host);
class obtainIP3 for(int i=0;i<adr.length;i++)
{ {
public static void main(String args [ ]) j++;
throws IOException System.out.println(j +"t" + adr[i]);
{ }
InetAddress adr[]; int j=0; }
String host;
DataInputStream input=new catch( UnknownHostException e)
DataInputStream(System.in); {
System.out.println("No such host exist");
System.out.println("Enter host "); }
host=input.readLine(); }
}

11. Output

12. getAddress() & getHostName()
import java.net.*;
class obtainIP4
{ public static void main(String args []) throws UnknownHostException
{
String msg;
byte num[];
InetAddress adr;
adr=InetAddress.getLocalHost();
num=adr.getAddress();
msg=adr.getHostName();
System.out.println("LocalHost= " + adr);
for(int i=0;i<num.length;i++)
{
msg +=(num[i] & 255) + ".";
System.out.println("Num= " + msg);
}
}
}

13. Output

14. Socket Class
O The Socket class ,basically used to create client sockets, is
designed to connect to server socket and initiate protocol
exchanges.
O When Socket object is created, it implicitly establishes the
connection b/w client and server.
O Socket defines the constructors to create client sockets.
Constructors:-
Socket(String hostname, int port);
Socket(InetAdrress ipaddr, int port);

15. Socket Class Methods
Methods:-
1)InputStream getInputStream();
1)OutputStream getOutputStream();
1)void close();

16. ServerSocket Class
The ServerSocket class, basically used to create server sockets,
is designed to be a listener, which waits for client to connect
before doing anything.
Constructors:-
ServerSocket ( int port );
ServerSocket ( int port, int queueLength);
Method:-
Socket accept();
accept() is a blocking call that waits for a client to initiate
communication and returns a normal Socket, that is used for
communication with the client.