Networking in Java

Networking in Java

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Networking in Java

Java is a premier language for network programming. java.net package encapsulates a large number of classes and interfaces that provide an easy-to-use means to access network resources. Here are some important classes and interfaces of java.net package.

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Some Important Classes

CLASSES
CacheRequest	CookieHandler
CookieManager	Datagram packet
Inet Address	ServerSocket
Socket	DatagramSocket
Proxy	URL
URLConnection

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Some Important Interfaces

INTERFACES
CookiePolicy	CookieStore
FileNameMap	SocketOption
InetAddress	ServerSocket
SocketImplFactory	ProtocolFamily

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InetAddress

Inet Address encapsulates both numerical IP address and the domain name for that address. Inet address can handle both IPv4 and Ipv6 addresses. Inet Address class has no visible constructor. To create an init Address object, you have to use Factory methods.

Three commonly used Inet Address factory methods are.

1. static InetAddress getLocalHost() throws UnknownHostException
2. static InetAddress getByName (String hostname) throws UnknownHostException
3. static InetAddress[ ] getAllByName (String hostname) throws UnknownHostException

Example using InetAddress class

import java.net.*;
class Test
{
 public static void main(String[] args)
 {
  InetAddress address = InetAddress.getLocalHost(); 
  System.out.println(address);
  address = InetAddress.getByName("www.studytonight.com");
  System.out.println(address);
  InetAddress sw[] = InetAddress.getAllByName("www.google.com");
  for(int i=0; i< sw.length; i++)
  {
   System.out.println(sw[i]);
  }
 }
}

Output:

Welcome-PC/59.161.87.227
www.studytonight.com/208.91.198.55
www.google.com/74.125.236.115
www.google.com/74.125.236.116
www.google.com/74.125.236.112
www.google.com/74.125.236.113
www.google.com/74.125.236.114
www.google.com/2404:6800:4009:802:0:0:0:1014

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Socket and ServerSocket Class

The socket is a foundation of modern networking, a socket allows a single computer to serve many different clients at once. Socket establishes a connection through the use of the port, which is a numbered socket on a particular machine. Socket communication takes place via a protocol. The socket provides a communication mechanism between two computers using TCP. There are two kinds of TCP sockets in Java. One is for server and other is for the client.

• ServerSocket is for servers.
• Socket class is for the client.

URL class

Java URL Class present in java.net package deals with URL (Uniform Resource Locator) which uniquely identify or locate resources on the internet

Important Methods of URL class

• getProtocol() : Returns protocol of URL
• getHost() : Returns hostname(domain name) of URL
• getPort() : Returns port number of URL
• getFile() : Returns filename of URL

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Program using URL class

import java.net.*;
class Test
{
 public static void main(String[] arg) throws MalFormedURLException 
 {
  URL hp = New URL("http://www.studytonight.com/index");
  system.out.println(hp.getProtocol[]); 
  System.out.println(hp.getFile[]);
 }
}

Ouput:

http
-1
www.studytonight.com 
/index