Java Network classes Part1


Java Networking Tutorial

 


coding-zon-java-networks-part1

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All network related classes are bundled in java.net package in Java Language. It includes various classes and interfaces for implementing networking applications. This tutorial gives you an overview of java.net package.


Classes and Interfaces available in Java.net Package



InetAddress

Inet4Address    |   are subclasses of InetAddress   
Inet6Address    |

 

URL
URLConnection
HttpURLConnection


Socket,             |
ServerSocket    |    These classes uses TCP, to communicate over the network.


DatagramPacket,     |
DatagramSocket,     |   These classes uses UDP  to communicate over the network.
MulticastSocket       |





Java programs can use both TCP or UDP based classes to communicate over the Internet.


TCP/IP based classes



Socket—Generally used by client program to communicate with the Server. A socket is one end-point
        of a two-way communication link between two programs running on the network.

ServerSocket → with the ServerSocket server listens client request.


Datagram based classes

 

DatagramSocket
DatagramPacket
 

 

 What is URL?


  Uniform Resource Locator(URL) is a reference/address
  to a resource on Internet.

        Ex: http://java.oracle.com

http://  → is a protocol identifier
java.oracle → a resource name
.com → is domain name

There are different domain names available. ex:
.com
.org
.net
.mil
.in
.edu etc.,

URL Class

 
To identify a resource java provides a class called  URL. which can allows to get various
information about url. to create url the following constructors can be used.

Constructors
 

URL(String url) throws MalformedURLException


URL(String protocolName,String hostName, int port,String path) throws MalformedURLException

URL(String protocolName,String hostName, String path) throws MalformedURLException

URL(URL urlObj ,String urlspecifier) throws MalformedURLException


syn1:

      URL u =  new URL("http://www.oracle.com/index.html");

syn2:

 

URL example = new URL("http", "www.example.com", 80,
                       "pages/example.index.html");



This creates a URL object for the following URL:

           

        www.example.com:80/pages/example.index.html




Methods
 

getProtocol() → The protocol on which it is communicating.
getPort() → The port number to which to connect (typically                optional).
getHost() → The name of the machine on which the resource lives.
getFile() → The path name to the file on the machine. 

//Demonstrate URL

import java.net.*;
import java.io.*;

class URLDemo{

 public static void main(String args[]) throws MalformedURLException{

 	URL hp =  new URL("http://www.oracle.com/index.html",80);

 	System.out.println("Protocol:"+hp.getProtocol());
 	System.out.println("Port:"+hp.getPort());
 	System.out.println("Host:"+hp.getHost());
 	System.out.println("File:"+hp.getFile());
 	System.out.println("Port:"+hp.toExternalForm());
}
}

 output:

H:\JavaNetworking>java URLDemo
Protocol:http
Port:-1
Host:www.oracle.com
File:/index.html
Port:http://www.oracle.com/index.html

 InetAddress Class

 

Internet addresses are represented in Java by the InetAddress class.
InetAddress provides simple methods to convert between domain names, and numbered addresses.
It allows to find Hostname,IPAddress.

    domainName    IPAddress
  
ex: localhost  ----  127.0.0.1


To create an InetAddress object, factory methods are used.
Factory methods are merely a convention whereby static methods in a class
returns an instance of that same class.

Static methods
 

static InetAddress getLocalHost() throws UnknownHostException

static InetAddress getByName(String hostName) throws UnknownHostException

static InetAddress[] getAllByName(String hostName) throws UnknownHostException



EX1:

// Demonstrate InetAddress. 

import java.net.*; 

class InetAddressTest 
{ 
public static void main(String args[]) throws UnknownHostException { 

InetAddress Address = InetAddress.getLocalHost(); 

System.out.println(Address); 

Address = InetAddress.getByName("google.com"); 

System.out.println(Address); 

InetAddress SW[] = InetAddress.getAllByName("http://www.oracle.com"); 

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

 output:

H:\JavaNetworking>javac InetAddressTest.java

H:\JavaNetworking>java InetAddressTest
hpsoma/192.168.1.4
oracle.com/138.1.33.162
www.google.com/142.250.183.196
www.google.com/2404:6800:4009:826:0:0:0:2004

URLConnection Class

URLConnection is a general-purpose class for accessing the attributes of a remote resource. 

//Demonstrate URLConnection 
 import java.net.*;
import java.io.*;
import java.util.*;

class UCDemo{

 public static void main(String args[]) throws Exception{

     int c;
     URL hp =  new URL("http://www.google.com");
     URLConnection hpCon= hp.openConnection();
     long d = hpCon.getDate();

    if(d==0)
       System.out.println("Content-Type:"+hpCon.getContentType());

        d= hpCon.getExpiration();

    if(d==0)
       System.out.println("No expiration information.");
    else
       System.out.println("Expires:"+ new Date(d));

        d= hpCon.getLastModified();

    if(d==0)
       System.out.println("No LastModified information." + new Date(d));

    int len= hpCon.getContentLength();

    if(len == -1)
       System.out.println("Content length is unavailable");
    else
       System.out.println("Content length : "+len);

    if(len != 0){
       System.out.println("=========Content=======");

       InputStream input = hpCon.getInputStream();
       int i=len;
       while(((c=input.read())!= -1)){
          System.out.println((char)c);
        }
       input.close();
       }
    else{

      System.out.println("No content is available.");
    }}}

 

output:

H:\JavaNetworking>javac UCDemo.java

H:\JavaNetworking>java UCDemo
No expiration information.
No LastModified information.Thu Jan 01 05:30:00 IST 1970
Content length is unavailable
=========Content=======
<!doctype html><html itemscope="" itemtype="http://schema.org/WebPage" lang="en-IN"><head><meta content="text/html; charset=UTF-8" http-equiv="Content-Type"><meta content="/logos/doodles/2022/2022-world-cup-opening-day-6753651837109999.4-law.gif" itemprop="image"><meta content="2022 World Cup - Opening Day!" property="twitter:title"><meta content="Let the games begin! #GoogleDoodle" pro.......

 

 

 

EX2:
 
import java.net.*;
import java.io.*;

class ConnectionTest {
    public static void main(String[] args) {
        try {
            URL google = new URL("http://www.google.com/");
            URLConnection googleConnection = google.openConnection();
            DataInputStream dis = new DataInputStream(googleConnection.getInputStream());

BufferedReader d
         = new BufferedReader(new InputStreamReader(dis));


            String inputLine;

            while ((inputLine = d.readLine()) != null) {
                System.out.println(inputLine);
            }
            dis.close();
        } catch (MalformedURLException me) {
            System.out.println("MalformedURLException: " + me);
        } catch (IOException ioe) {
            System.out.println("IOException: " + ioe);
        }
    }
}

 output:

H:\JavaNetworking>javac ConnectionTest.java

H:\JavaNetworking>java ConnectionTest
<!doctype html><html itemscope="" itemtype="http://schema.org/WebPage" lang="en-IN"><head><meta content="text/html; charset=UTF-8" http-equiv="Content-Type"><meta content="/logos/doodles/2022/2022-world-cup-opening-day-6753651837109999.4-law.gif" itemprop="image"><meta content="2022 World Cup - Opening Day!" property="twitter:title"><meta content="Let the games begin! #GoogleDoodle" property="....
 


 


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