Java NetWorking(URL , SOCKET(TCP/IP),DATAGRAMS)- I

 

NetWorking(URL , SOCKET(TCP/IP),DATAGRAMS)- I

Java supports Networking and its creators have called java as "programming for the Internet".

Types of Network Programming

Two general types are:

·    Connection-Oriented Programming

·    Connectionless Programming

Connection-Oriented Networking

The Client and Server have a communication link that is open and active from the time the application is executed until it is closed.Using Internet Jargon,the Transmission control protocol is a connection oriented protocol.It is reliable connection -packets are guaranteed to arrive in the order they are sent

 

Connection-less Oriented Networking

The this type each instance that packets are sent ,they are transmitted individually. No link to the receiver is maintained after the packets arrive.

The Internet equivalent is the user Datagram Protocol(UDP). Connectionless communication is faster but not reliable. Datagrams are used to implement a connectionless protocol,suchas UDP.

 

SocketOverview

A network socket is a lot like an electrical socket.

Internet Protocol(IP) is a Low-Level routing Protocol that breaks data into small packets and sends them to an address across a network,which does not guarantee to deliver said packets to the desination.Transmission Control Protocol(TCP) is a higher-level protocol that manages to robustly string together these packets,sorting and retransmitting them as necessary to reliably transmit your data.A third protocol, user Datagram Protocol(UDP),sits next to TCP and can be used directly to support fast,connectionless,unreliable transport of packets.

Client/Server

A server is anything that has some resource that can be shared.there are compute servers,which provide networked disk spaces;and web servers,which store web page.A client is simply any other entity that wants to gain access to a particular server.the interaction between client and server is just like interaction between a lamp and an electrical socket.

Reserved Sockets

Once Connected,a higher-level protocol ensues,which is dependent on which port you are using.TCP/IP reserves the lower 1024 ports for specific protocols.

Proxy Servers

A proxy server speaks the client side of a protocol to another server.

Internet Addressing

Every computer on the Internet has an address.An Internet Address is a number that uniquely identifies each computer on the net.Originally,all Internet address consisted of 32-bit values

Domain Naming Service(DNS)

The Internet wouldn't be a very friendly place to navigate if everyone had to refer to their address as numbers.Forexample,it is difficult to imagine seeing "http://192.9.9.1/" at the bottom of an advertisement.Thankfully,a clearing house exists for a parallel hierarchy of names to go with all these numbers. It is called the DomainNamingService(DNS).just as the four numbers of an IP address describe a network hierarchy from left to right,the name of an Internet address,called its domain name ,describes a machine's location in a name space,from right to left For example,www.osborne.com is in the COM domain(reserved for U.S.commercial sites),it is called Osborne (after the company name), and www is the name of the specific computer that is Osborne's web server.www corresponds to the rightmost number in the equivalent IP address.

  

 JAVA AND THE NET

Inet Address Class

The InetAddress class is used to encapsulate both the numerical IP address and the domain name for that address. you interact with this class by using the name of an IP host,which is more convenient and understandable than its IP address. the Inet Address class hides the number inside.

METHODS

static InetAddress getLocalHost()throws unknown HostException.

static InetAddress getByName(StringhostName)throws unknown HostException.

 static InetAddress[] getAllbynames(StringhostName)throws unknown HostException.

TCP/IPClientSockets

TCP/IP sockets are used to implement reliable,bidirectional,persistent,point-to-point, stream-based connection between hosts on the Internet.A sockets can be used to connect java's I/O system to other program that may reside either on the local machine or on any other machine on the internet.

Socket(StringhostName,int port)->creates a socket connecting the local host to the named host and port;can throw an UnknownHostException or an IOException.

Socket(InetAddressipAddress.intport)

->creates a socket using a preexisting InetAddress Object and a port;can throw an IOException.

A socket can be examined at any times for the address and the port information associated with it by use of the following methods:

InetAddress getInetAddress()->Returns the InetAddress associated with the socket object .

intgetPort()->Return the remote port to which this socket object is connected.

intgetPort()->Returns the local port to which this socket object is connected.

The serversocket class is used to create serves that listen for either local or remote client programs to connect to them on Published ports.

serversockets  are quit different from normal sockets.when can you create a serversocket,it will register itself with the system as having an interest in client connections.

Constructors

serversocket(int port)->creates server socket on the specified port with a queue length of 50.

 serversocket(int port,int maxQueue)

->creates server socket on the specified port with a maximum queue length of maxQueue.

serversocket(intport,int maxQueue,InetAddresslocalAddress)

->creates server socket on the specified port with a maximum Queue length of maxQueue.on a multihomed host,localAddress specifies the IP address to which this socket binds.

INetAddress Class

Program:

File name: Ip.java

import java.net.*;

import java.io.*;

public class Ip

{

public static void main(String[] args)throws IOException

{

String hostname="";

try

{

InetAddress ipaddress=InetAddress.getByName(hostname);

System.out.println("IP Address:"+ipaddress.getHostAddress());

}

catch(UnknownHostException e){

System.out.println("Could not find IP address for:"+hostname);

}

}

}

 

Output

 

Constructors

Server Program

File name: Server.java

import java.net.*;

import java.lang.*;

import java.io.*;

public class Server{

public static final int PORT=1025;

public static void main(String args[])

{

ServerSocket sersock=null;

Socket sock=null;

System.out.println(" Wait !! ");

try{

sersock=new ServerSocket(PORT);

int number;

System.out.println("Server Started :"+sersock);

sock=sersock.accept();

System.out.println("Client Connected:"+sock);

DataInputStream ins=new DataInputStream(sock.getInputStream());

String clientMsg=new String(ins.readUTF());

System.out.println(clientMsg);

DataOutputStream dos=new DataOutputStream(sock.getOutputStream());

dos.writeUTF("Hello from Server");

dos.close();

sock.close();

}

catch(SocketException se)

{

System.out.println("Server Socket Problem"+se.getMessage());

}

catch(Exception e){

System.out.println("Couldn't start"+e.getMessage());

}

System.out.println("Connection from:"+sock.getInetAddress());

}

}

 

Client Program

File name: Client.java

import java.lang.*;

import java.io.*;

import java.net.*;

import java.net.InetAddress;

class Client{

public static void main(String args[]){

Socket sock=null;

DataInputStream dis=null;

DataOutputStream dos=null;

System.out.println("Trying to Connect");

try{

InetAddress ip=InetAddress.getByName("localhost");

sock=new Socket(ip,Server.PORT);

dos=new DataOutputStream(sock.getOutputStream());

dos.writeUTF("Hi from Client");

DataInputStream is=new DataInputStream(sock.getInputStream());

String serverMsg=new String(is.readUTF());

System.out.println(serverMsg);

}

catch(SocketException e){

System.out.println("SocketException "+e);

}

catch(IOException e){

System.out.println("IOException "+e);

}

finally{

try{

sock.close();

}

catch(IOException ie){

System.out.println("Close Error: "+ie.getMessage());

}

}

}

}

Open Two CMD. Run One Cmd Server , and another Cmd Client.First Run Server.After Run Client Program.

Output

Before connecting Client , Server Output

 

After connecting Client , Server and Client Output