NETWORK PROGRAMMING LAB(JAVA)
This PPT is Dedicated to my inner controller
AMMA BHAGAVAN – ONENESS Founders.
Developed by,
S.V.G.REDDY,
Associate professor,
Dept.of CSE, GIT,
GITAM UNIVERSITY.
EDITED BY,
M.Siva Naga Prasad
student of M.tech(SE).
WELL KNOWN PORTS
Program:
import java.io.*;
import java.net.*;
class wkports
{
public static void main(String args[])
{
for(int i=100;i<200;i++)
{
try
{
Socket s=new Socket(host,i);
System.out.println("There is a server on port :"+ i +" of: " +host);
}
catch(UnknownHostException e)
{
System.err.println(e);
}
catch(IOException ie)
{
System.out.println(ie.getMessage());
} } }}
Output:-
One to One Chat Application
•One-to-one communication is the act of an
individual communicating with another.
• In Internet terms, this can be done by e-mail but
the most typical one-to-one communication in the
Internet is instant
messaging as it does not consider many-to-many
communication such as a chat room as an
essential part of its scope
DESCRIPTION






The program displays what is written by one party to another
by opening a socket connection
The Application contains two classes:
1.Chat client
2.Chat server
The chat server class creates class creates a serves
socket object which listens on port 9999.The server socket
accepts client socket and reads whatever is written by client
and sends the message to the client thus allowing One-one
communication
The Chat client class creates a socket object using which
it sends message to the server on port 9999.The
communication ends when the client send server says “bye”.
TOPICS INCLUDED IN THIS…….
Socket Programming
 Exception Handling
 I/O and StreamClasses

SOCKET PROGRAMMING:

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. The
java.net package provides two classes--Socket
and Server Socket--that implement the client
side of the connection and the server side of
the connection, respectively.
EXCEPTION HANDLING:
What is Exception???
 An exception is an event that occurs during the execution of a
program that disrupts the normal flow of instructions.
Why Exception Handling??
 To terminate the program neatly in error condition or unexpected
scenario.
 To fix the problem at run time
 To give user friendly messages to end user in case of unusual
scenario or error
EXCEPTION HANDLING USING JAVA:

When an error occurs within a method, the method
creates an object and hands it off to the runtime system.
The object, called an exception object, contains
information about the error, including its type and the
state of the program when the error occurred. Creating an
exception object and handing it to the runtime system is
called throwing an exception.
In java Exception handling is achieved by using
Try , Catch and Finally Blocks of code.
 The Super class for all types of exceptions in java is
java.lang.Exception

TRY BLOCK
try
{
code
}
CATCH BLOCK
catch (Exception ex)
{
<do something with ex>
}

catch
 A method can catch an exception by providing an exception handler
for that type of exception.
Client side program:
import java.io.*;
import java.net.*;
import java.lang.*;
public class chatclient1
{
public static void main(String args[]) throws IOException
{
Socket csoc=null;
String host;
if(args.length>0)
host=args[0];
else
host="localhost";
PrintWriter pout=null;
BufferedReader bin=null;
try
{
csoc=new Socket(host,7);
pout=new PrintWriter(csoc.getOutputStream(),true);
bin=new BufferedReader(new
InputStreamReader(csoc.getInputStream()));
}
catch(UnknownHostException e)
{
System.err.println("Unknownhost");
System.exit(1);
}
catch(IOException e)
{}
BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
String input;
while(true)
{
input=in.readLine();
pout.println(input);
String msg=bin.readLine();
System.out.println("client :"+msg);
if(msg.equals("bye"))
break;
}
in.close();
pout.close();
bin.close();
csoc.close();
}
}
Server side program:
import java.io.*;
import java.net.*;
import java.lang.*;
public class chatserver1
{
public static void main(String args[]) throws IOException
{
ServerSocket ssoc=null;
try
{
ssoc=new ServerSocket(7);
}
catch(IOException e)
{
System.err.println("No connection established");
System.exit(1);
}
Socket csoc=null;
try
{
csoc=ssoc.accept();
}
catch(IOException e)
{
System.err.println("Not accepted");
System.exit(1);
}
PrintWriter pw=new PrintWriter(csoc.getOutputStream(),true);
BufferedReader br=new BufferedReader(new
InputStreamReader(csoc.getInputStream()));
String inline;
String outline;
try
{
DataInputStream din=new DataInputStream(System.in);
while(true)
{
inline=br.readLine();
System.out.println("Server :"+inline);
outline=din.readLine();
pw.println(outline);
if(outline.equals("bye"))
break;
}
}
catch(Exception e)
{
System.err.println(e);
}
pw.close();
br.close();
csoc.close();
ssoc.close();
}
}
Server side output window:
Clint side output window:
MANY TO MANY CHAT APPLICATION
DESCRIPTION:

Each client opens a socket connection to the chat
server and writes to the socket whatever is written by
one party can be seen by all other parties.

Chat Rooms in yahoo is the best example for this
many to many chat application.
Connections Between Systems
CONCEPTS BEHIND THIS
Socket communication
 Exception Handling
 IO
 Multi Threading

SOCKET PROGRAMMING

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. The
java.net package provides two classes--Socket
and Server Socket--that implement the client
side of the connection and the server side of
the connection, respectively.
CLASSES IN THIS PROGRAM:




It Reads text from a character-input stream, buffering
characters so as to provide for the efficient reading of
characters, arrays, and lines
It belongs to java.io Package.
BufferedReader (Reader in)
Create a buffering character-input stream that
uses a default-sized input buffer.
Methods In This Class…
ReadLine(): Read a line of text. A line is considered
to be
terminated by any one of a line feed
('\n'), a carriage return ('\r'), or a carriage return
followed immediately by a linefeed
Print Writer:


Print formatted representations of objects to a text-output
stream.
public PrintWriter(OutputStream out,boolean autoFlush)
Create a new PrintWriter from an existing OutputStream.
This convenience constructor creates the necessary
intermediate OutputStreamWriter, which will convert
characters into bytes using the default character
encoding.
GET INPUT/OUTPUT STREAM
InputStream
 Returns an input stream for socket.
 This method is Belongs socket class.
 Socket class is belongs to java.net. Package
OutPutStream
 Returns an output stream for socket.
INPUT STREAM READER
An InputStreamReader is a bridge from byte
streams to character streams: It reads bytes and
decodes them into characters using a specified
charset. The charset that it uses may be specified
by name or may be given explicitly, or the
platform's default charset may be accepted.
 Public InputStreamReader(InputStream in) :
Create an InputStreamReader that uses the
default charset.

DATAINPUTSTREAM
A data input stream lets an application read
primitive Java data types from an underlying
input stream in a machine-independent way.
An application uses a data output stream to
write data that can later be read by a data
input stream.
 public DataInputStream(InputStream in) :
Creates a DataInputStream that uses the
specified underlying InputStream

MULTI THREADING

Thread is a Active part of execution.

Thread is a path of execution.

Threads are also called as lightweight process

Threads are executed in parallel.
MULTITHREADING USING JAVA
We can implement multi threading using java
in 2 ways
 1.)By inheriting Thread class
or
 2.)By Implementing RUNNABLE interface

THREAD CLASS
To implement Multi threading we have to
override the run method of Thread class
 Thread class is belongs to java.lang. package
 Methods in this class
 Start(),run(),sleep(),stop(),join()…e.t.c.

RUNNABLE INTERFACE
This is an interface with only one method
 That is RUN()
 By implementing this interface we can get
multi threading

CLIENT SIDE PROGRAM :
import java.net.*;
import java.io.*;
public class mclient
{
public static void main(String a[])
{
BufferedReader in;
PrintWriter pw;
try
{
Socket s = new Socket("localhost",118);
System.out.println("Enter name");
in = new BufferedReader(new InputStreamReader(System.in));
String msg = in.readLine();
pw = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
pw.println(msg+"\n");
pw.flush();
while(true)
{
readdata rd = new readdata(s);
Thread t = new Thread(rd);
t.start();
msg = in.readLine();
if(msg.equals("quit"))
{
System.exit(0);
}
pw.println(msg);
pw.flush();
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
class readdata implements Runnable
{
public Socket s;
public readdata(Socket s)
{
this.s = s;
}
public void run()
{
BufferedReader br;
try
{
while(true)
{
br = new BufferedReader(new InputStreamReader(s.getInputStream()));
String msg = br.readLine();
System.out.println(msg);
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
SERVER SIDE PROGRAM :
import java.net.*;
import java.io.*;
public class mserver
{
public static Socket s[] = new Socket[10];
public static String user[] = new String[10];
public static int total;
public static void main(String a[])
{
int i=0;
try
{
ServerSocket ss = new ServerSocket(118);
while(true)
{
s[i] = ss.accept();
BufferedReader br = new BufferedReader(new InputStreamReader(s[i].getInputStream()));
String msg = br.readLine();
user[i] = msg;
System.out.println(msg+" connected") ;
try
{
reqhandler req = new reqhandler(s[i],i);
total = i;
i++;
Thread t = new Thread(req);
t.start();
}
catch(Exception e)
{
System.out.println(e);
}
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}
class reqhandler implements Runnable
{
public int n;
public Socket s;
public reqhandler(Socket soc,int i)
{
s = soc;
n = i;
}
public void run()
{
String msg = "";
BufferedReader br,br1;
PrintWriter pw;
try
{
while(true)
{
br1 = new BufferedReader(new InputStreamReader(System.in));
if((br1.readLine()).equals("quit"))
System.exit(0);
br = new BufferedReader(new InputStreamReader(s.getInputStream()));
msg = br.readLine();
if(msg.equals("quit"))
mserver.total--;
else
System.out.println(mserver.user[n]+"->"+msg);
if(mserver.total == -1)
{
System.out.println("Server Disconnected");
System.exit(0);
}
for(int k=0;k<=mserver.total;k++)
if(!mserver.user[k].equals(mserver.user[n])&&(!msg.equals("quit")))
{
pw = new PrintWriter(new OutputStreamWriter(mserver.s[k].getOutputStream()));
pw.println(mserver.user[n]+":"+msg+"\n");
pw.flush();
}
}
}
}
catch(Exception e)
{
}
}
}
OUTPUT:
Output:
Server
2. Access to data base
Data base
Client
Server
Server side program:
Listening to the port,
Establishing connections
Reading from and writing to the socket.
A socket is an end point for communication between two
machines
Server
ServerSocket ssoc=new ServerSocket(1111);
This ServerSocket object is used to listen on a port
Port is an address that identifies the
particular application in destination machine
192.256.17.25
Port:
1111
Establishing connections
Server
Accepting the connection
Socket csoc=ssoc.accept();
Client
Client socket object which is bound to same local port(1111)
The communication is done through the new socket object
In Server program:
BufferedReader fromc= new BufferedReader(new
InputStreamReader(csoc.getInputStream()))
csoc.getInputStream:
It reads input from socket object
PrintStream toc=new
PrintStream(csoc.getOutputStream());
csoc.getOutputStream:
It writes stream of data to socket object
In client program:
PrintStream tos=new PrintStream(soc.getOutputStream());
It writes stream of data to socket object
BufferedReader froms=new BufferedReader(new
InputStreamReader(soc.getInputStream()));
It reads input from socket object
BufferedReader fromkb=new BufferedReader(new
InputStreamReader(System.in));
Takes the input from keyboard
Connecting to data base
Server
Load the Driver class
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Server
Connection conn =
DriverManager.getConnection("jdbc:odbc:dns",“userid",“password");
Server
Ready to execute queries
interface
Statement stmt=conn.createStatement();
Statement object is created for executing the SQL queries
Server
String query=fromkb.readLine();
Pose a query
Send to server
tos.println(query);
Client
Server
query=fromc.readLine();
Client
Metadata
if(query.equalsIgnoreCase("quit"))
break;
ResultSetMetaData rsmd=rs.getMetaData();
ResultSet rs=stmt.executeQuery(query);
int noCol=rsmd.getColumnCount();
Gets the field
names from
the tables
if(rs.next())
{
rset=new StringBuffer("RESULT:\n");
for(int i=1;i<=noCol;i++)
rset.append(rsmd.getColumnLabel(i)+"\t");
rset.append("\n");
}
do
{
for(int i=1;i<=noCol;i++)
rset.append(rs.getString(i)+"\t");
rset.append("\n");
}while(rs.next());
Gets the
values from
the tables
Server
toc.print(rset);
Client
query=froms.readLine();
All the data retrieved is said to be returned to the client through
rset object
System.out.println(query);
Field 1
Field 2
xxxx
yyyyy
zxzxzx
zzzzz
Server
Client
conn.close();
Server side program:
import java.io.*;
import java.net.*;
import java.sql.*;
class rdbserver
{
public static void main(String args[])
{
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
try
{
ServerSocket ssoc=new ServerSocket(1111);
System.out.println("wait for client connection:\n");
Socket csoc=ssoc.accept();
if(csoc!=null)
System.out.println("client is connected:");
BufferedReader fromc=new BufferedReader(new
InputStreamReader(csoc.getInputStream()));
PrintStream toc=new PrintStream(csoc.getOutputStream());
BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
String query="";
StringBuffer rset=null;
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
conn=DriverManager.getConnection("jdbc:odbc:vinod","scott","tiger");
stmt=conn.createStatement();
do
{
query=fromc.readLine();
System.out.println("client query request:"+query);
if(query.equalsIgnoreCase("quit"))
break;
rs=stmt.executeQuery(query);
ResultSetMetaData rsmd=rs.getMetaData();
int noCol=rsmd.getColumnCount();
if(rs.next())
{
rset=new StringBuffer("RESULT:\n");
for(int i=1;i<=noCol;i++)
rset.append(rsmd.getColumnLabel(i)+"\n");
rset.append("\n");
}
Do
{
for(int i=1;i<=noCol;i++)
rset.append(rs.getString(i)+"\t");
rset.append("\n");
}
while(rs.next());
rset.append("");
toc.println(rset);
}
while(!query.equalsIgnoreCase("quit"));
conn.close();
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
}
Clint side program:
import java.io.*;
import java.net.*;
import java.sql.*;
public class rdbclient
{
public static void main(String args[])
{
System.out.println("connected to serverdata");
try
{
Socket soc=new Socket("localhost",1111);
PrintStream tos=new PrintStream(soc.getOutputStream());
BufferedReader froms=new BufferedReader(new
InputStreamReader(soc.getInputStream()));
BufferedReader fromkb=new BufferedReader(new
InputStreamReader(System.in));
String query="";
System.out.println("connected:\n");
System.out.print("enter query:");
do
{
query=fromkb.readLine();
tos.println(query);
if(query.equalsIgnoreCase("quit"))
break;
do
{
query=froms.readLine();
System.out.println(query);
}
while(!query.startsWith(""));
}
while(!query.equalsIgnoreCase("quit"));
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Server side output window:
Clint side output window:
SIMPLE MAIL TRANSFER PROTOCOL
PROGRAM:
/*import the packages needed for email and gui support*/
import java.net.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
/*** This class defines methods that display the gui and handle the sending of
*mails to the Mail server. */
public class SMTP extends WindowAdapter implements ActionListener
{
private Button sendBut = new Button("Send Message");
private Label fromLabel = new Label(" From : ");
private Label toLabel = new Label("
To : ");
private Label hostLabel = new Label("Host Name : ");
private Label subLabel = new Label(" Subject : ");
private TextField fromTxt = new TextField(25);
private TextField toTxt = new TextField(25);
private TextField subTxt = new TextField(25);
private TextField hostTxt = new TextField(25);
private TextArea msgTxt = new TextArea();
private Frame clientFrame = new Frame("SMTP Client");
/*** Constructor with takes no parameters.
* this constructor displays the window for the user to
* assist in sending emails. */
public SMTP()
{
clientFrame.setLayout(new GridLayout(2,1));
Panel p1 = new Panel();
p1.setLayout(new GridLayout(4,1));
Panel p11 = new Panel();
p11.setLayout(new FlowLayout());
p11.add(hostLabel);
p11.add(hostTxt);
Panel p12 = new Panel();
p12.setLayout(new FlowLayout());
p12.add(fromLabel);
p12.add(fromTxt);
Panel p13 = new Panel();
p13.setLayout(new FlowLayout());
p13.add(toLabel);
p13.add(toTxt);
Panel p14 = new Panel();
p14.setLayout(new FlowLayout());
p14.add(subLabel);
p14.add(subTxt);
p1.add(p11);
p1.add(p12);
p1.add(p13);
p1.add(p14);
Panel p2 = new Panel();
p2.setLayout(new BorderLayout());
p2.add(msgTxt,BorderLayout.CENTER);
Panel p21 = new Panel();
p21.setLayout(new FlowLayout());
p21.add(sendBut);
p2.add(p21,BorderLayout.SOUTH);
clientFrame.add(p1);
clientFrame.add(p2);
clientFrame.setSize(400,500);
clientFrame.setVisible(true);
clientFrame.addWindowListener(this);
sendBut.addActionListener(this);
}
/** * This method is triggered when the close button of a window
* is closed. The method exits the application. */
public void windowClosing(WindowEvent we)
{
clientFrame.setVisible(false);
System.exit(1);
}
/** * This method is called in response to button clicks.
* The method reads the message to be sent, packs it in
* a Message object and sends it to the mail server. */
public void actionPerformed(ActionEvent ae)
{
try
{
Socket s=new Socket(hostTxt.getText(),25);
BufferedReader br=new BufferedReader(new
InputStreamReader(s.getInputStream()));
PrintWriter pw=new PrintWriter(s.getOutputStream(),true);
System.out.println("Connection is established");
pw.println("HELLO");
System.out.println(br.readLine());
pw.println("MAIL From:"+fromTxt.getText());
System.out.println(br.readLine());
pw.println("RCPT To:"+toTxt.getText());
System.out.println(br.readLine());
pw.println("DATA");
pw.println(msgTxt.getText()+"\n.\n");
System.out.println(br.readLine());
pw.println("QUIT");
pw.flush();
s.close();
System.out.println("Mail has been sent....");
}
catch(Exception e)
{
}
System.out.println("Connection Terminated");
}
/*** This is the main method . It instantiates an object of this
* class (SMTPClient) and adds listeners for the frame window
* and the buttons used in the gui. */
public static void main(String args[])
{
SMTP client = new SMTP();
}
}
OUTPUT:
POP CLIENT’S
POP CLIENT


Short for Post Office Protocol, a protocol used
to retrieve e-mail from a mail server. Most email applications (sometimes called an e-mail
client) use the POP protocol, although some
can use the newer IMAP (Internet Message
Access Protocol).
There are two versions of POP. The first, called
POP2, became a standard in the mid-80's and
requires SMTP to send messages. The newer
version, POP3, can be used with or without
SMTP. POP3 uses TCP/IP port 110.

With IMAP, all your mail stays on the server in multiple
folders, some of which you have created. This enables
you to connect to any computer and see all your mail and
mail folders. In general, IMAP is great if you have a
dedicated connection to the Internet or you like to check
your mail from various locations.

With POP3 you only have one folder, the Inbox folder.
When you open your mailbox, new mail is moved from
the host server and saved on your computer. If you want
to be able to see your old mail messages, you have to go
back to the computer where you last opened your mail.

With POP3 "leave mail on server" only your email
messages are on the server, but with IMAP your email
folders are also on the server.
POP3 CLIENT APPLICATION
EMAIL SERVICES & SMTP/POP PROTOCOLS




Post Office Protocol (POP) and Simple Mail Transfer
Protocol (SMTP) are involved in email services.
Users use an application called a Mail User Agent
(MUA), or e-mail client to allow messages to be sent and
places received messages into the client's mailbox.
In order to receive e-mail messages from an e-mail
server, the e-mail client can use POP.
Sending e-mail from either a client or a server uses
message formats and command strings defined by the
SMTP protocol.
MAIL TRANSFER AGENT (MTA)
MAIL DELIVERY AGENT (MDA)

POP
SMTP
SERVER SIDE PROGRAM :
/*POP Client :gives the server name,username and password,retrieve
the mails and allow manipulation of mailbox using POP commands*/
import java.io.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
import java.awt.event.*;
class pop extends JFrame implements ActionListener
{
JPanel jp;
JLabel lpadd,lpnum,lpass,lretr,luser;
JTextField padd,pnum,user,retr,del;
JPasswordField pass;
JTextArea receive;
JScrollPane scrlp;
JButton login,list,quit,retrv,dele;
Socket s;
PrintWriter pw;
BufferedReader br;
int nmesgs;
pop()
{
jp=new JPanel();
jp.setLayout(null);
lpadd=new JLabel("port address");
lpadd.setBounds(20,20,100,20);
jp.add(lpadd);
padd=new JTextField();
padd.setBounds(110,20,120,20);
jp.add(padd);
lpnum=new JLabel("port number");
lpnum.setBounds(20,40,100,20);
jp.add(lpnum);
pnum=new JTextField();
pnum.setBounds(110,40,120,20);
jp.add(pnum);
login=new JButton("login");
login.setBounds(20,100,210,20);
jp.add(login);
login.addActionListener(this);
luser=new JLabel("user name");
luser.setBounds(20,60,100,20);
jp.add(luser);
user=new JTextField();
user.setBounds(110,60,120,20);
jp.add(user);
lpass=new JLabel("password");
lpass.setBounds(20,80,100,20);
jp.add(lpass);
pass=new JPasswordField();
pass.setBounds(110,80,120,20);
jp.add(pass);
list=new JButton("list");
list.setBounds(20,120,210,20);
list.addActionListener(this);
jp.add(list);
retrv=new JButton("retrieve");
retrv.setBounds(130,145,130,20);
jp.add(retrv);
retrv.addActionListener(this);
dele=new JButton("delete");
dele.setBounds(130,165,130,20);
jp.add(dele);
dele.addActionListener(this);
lretr=new JLabel("enter the meg numebr");
lretr.setBounds(20,145,120,20);
jp.add(lretr);
retr=new JTextField();
retr.setBounds(100,145,30,20);
retr.addActionListener(this);
jp.add(retr);
del=new JTextField();
del.setBounds(100,165,30,20);
del.addActionListener(this);
jp.add(del);
receive=new JTextArea();
receive.setEditable(false);
scrlp=new JScrollPane(receive);
jp.add(scrlp);
scrlp.setBounds(20,200,300,200);
quit=new JButton("quit");
quit.setBounds(130,410,80,30);
jp.add(quit);
quit.addActionListener(this);
setTitle("Post Office Protocol");
setSize(350,470);
show();
this.getContentPane().add(jp);
setVisible(true);
}
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource()==login)
{
try
{
s=new Socket(padd.getText(),Integer.parseInt(pnum.getText()));
br=new BufferedReader(new InputStreamReader(s.getInputStream()));
pw=new PrintWriter(new
OutputStreamWriter(s.getOutputStream()),true);
receive.setText(br.readLine()+"\n");
pw.println("user"+user.getText());
receive.append(br.readLine()+"\n");
pw.println("pass"+pass.getText());
receive.append(br.readLine()+"\n");
}
catch(IOException e)
{
JOptionPane.showMessageDialog(new JPanel(),"connection can not
be established");
}
}
if(ae.getSource()==list)
{
StringTokenizer st;
String str;
pw.println("list");
try
{
str=br.readLine();
st=new StringTokenizer(str);
st.nextToken();
str=st.nextToken();
nmesgs=Integer.parseInt(str)+1;
for(int i=0;i<nmesgs;i++)
receive.append(br.readLine()+"\n");
receive.append("no of messages :" + str + "\n");
}
catch(Exception e)
{
JOptionPane.showMessageDialog(new JPanel(),e);
}
}
if(ae.getSource()==retrv)
{
String k=retr.getText().trim();
pw.println("RETR \n"+k);
int l=Integer.parseInt(k);
try
{
String st=br.readLine();
if(l<nmesgs&&l>0)
{
while(!st.equals("."))
{
receive.append(st+"\n");
st=br.readLine();
}
}
else
{
receive.append(st+"\n");
}
retr.setText("");
}
catch(Exception e)
{
JOptionPane.showMessageDialog(new JPanel(),e);
}
}
if(ae.getSource()==quit)
System.exit(0);
if(ae.getSource()==dele)
{
try
{
pw.println("dele"+del.getText().trim());
nmesgs--;
del.setText("");
receive.append(br.readLine()+"\n");
}
catch(Exception e)
{
JOptionPane.showMessageDialog(new JPanel(),e);
}
}
}
public static void main(String args[])
{
pop p=new pop();
}
}
Clint side program:
import java.io.*;
import java.net.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class POPClient extends Frame implements ActionListener
{
TextField user,pass,host,msgno;
TextArea msgta;
Button signin,disp,prev,next,exit;
int no_of_msg,n;
String str;
BufferedReader br1,br2;
PrintWriter pw;
Socket s=null;
public POPClient()
{
super("POP");
user=new TextField(20);
pass=new TextField(20);
host=new TextField(20);
msgno=new TextField(20);
msgta=new TextArea("",10,50);
signin=new Button("LOGIN");
disp=new Button("DISPLAY");
next=new Button("NEXT");
prev=new Button("PREVIOUS");
exit=new Button("EXIT");
no_of_msg=0;
str=" ";
n=0;
Panel p1 = new Panel();
Panel p2 = new Panel();
Panel p3 = new Panel();
Panel p4 = new Panel();
setLayout(new GridLayout(3,1));
setSize(400,400);
p1.setLayout(new GridLayout(4,1));
Panel p11 = new Panel();
p11.add(new Label("User Name : "));
p11.add(user);
Panel p12 = new Panel();
p12.add(new Label("Password : "));
p12.add(pass);
Panel p13 = new Panel();
p13.add(new Label("Host Name : "));
p13.add(host);
Panel p14 = new Panel();
p14.add(signin);
p1.add(p11);
p1.add(p12);
p1.add(p13);
p1.add(p14);
p3.setLayout(new GridLayout(1,1));
p3.add(msgta);
p4.setLayout(new GridLayout(3,1));
Panel p41 = new Panel();
p41.add(new Label("Enter message number :"));
p41.add(msgno);
Panel p42 = new Panel();
p42.add(disp);
p42.add(new Label(" "));
p42.add(prev);
Panel p43 = new Panel();
p43.add(next);
p43.add(new Label(" "));
p43.add(exit);
p4.add(p41);
p4.add(p42);
p4.add(p43);
add(p1);
add(p4);
add(p3);
setVisible(true);
pass.setEchoChar('*');
signin.addActionListener(this);
disp.addActionListener(this);
prev.addActionListener(this);
next.addActionListener(this);
exit.addActionListener(this);
}
public void actionPerformed(ActionEvent ae)
{
try
{
if(ae.getSource()==signin)
{
s=new Socket(host.getText(),110);
br1=new BufferedReader(new
InputStreamReader(s.getInputStream()));
pw=new PrintWriter(s.getOutputStream(),true);
msgta.append(br1.readLine());
System.out.println("1");
pw.println("user "+user.getText());
System.out.println("2");
msgta.append("\n"+br1.readLine());
pw.println("PASS "+pass.getText());
System.out.println("3");
msgta.append("\n"+br1.readLine());
pw.println("list");
str=br1.readLine();
msgta.append("\n"+str);
StringTokenizer st=new StringTokenizer(str);
String tmpstr=st.nextToken();
tmpstr=st.nextToken();
no_of_msg=Integer.parseInt(tmpstr);
while(!(br1.readLine().equals(".")));
}
if(ae.getSource()==disp)
{
n=Integer.parseInt(msgno.getText());
display();
}
if(ae.getSource()==next)
{
n++;
display();
}
if(ae.getSource()==prev)
{
n--;
display();
}
if(ae.getSource()==exit)
{
if(s!=null)
s.close();
System.out.println("Connection terminated....");
System.exit(1);
}
}
catch(Exception c)
{
System.out.println(c);
}
}
void display()
{
msgta.setText("");
msgno.setText(String.valueOf(n));
if(n>0&&n<=no_of_msg)
{
System.out.println("N:"+n);
pw.println("retr "+n);
do
{
try
{
str=br1.readLine();
}
catch (Exception e)
{}
System.out.println("msg"+str);
msgta.append("\n"+str);
}while(!str.equals("."));
}
else
msgta.setText("You have "+no_of_msg+" mails");
}
public static void main(String args[])
{
POPClient p=new POPClient();
}
}
FILE TRANSFER PROTOCOL
WHAT IS FILE TRANSFER PROTOCOL (FTP)?
FTP is…
 a standard network protocol used to
exchange and manipulate files over a
TCP/IP-based network, such as the Internet.

built on a client-server architecture and
utilizes separate control and data
connections between the client and server
applications.
WHAT IS FILE TRANSFER PROTOCOL (FTP)?
FTP differs from other client-server
applications, it establishes two connections
between the hosts
 The first one is a data transfer connection
which does Data Transfer Process ( DTP )
 The other is a control information connection
which interprets FTP commands through
Protocol Interpreter

WHAT IS FTP USED FOR?
FTP is used to:
 Promote sharing of files (computer programs
and/or data)

Transfer data reliably, and efficiently
CLIENT SIDE PROGRAM :
import java.net.*;
import java.io.*;
public class ftpclient
{
public static void main (String args[])
{
Socket s;
BufferedReader in, br;
PrintWriter pw;
String spath,dpath;
FileOutputStream fos;
int c;
try
{
s = new Socket ("localhost",1111);
in = new BufferedReader (new InputStreamReader (System.in));
br = new BufferedReader (new InputStreamReader (s.getInputStream()));
pw = new PrintWriter(s.getOutputStream(), true);
System.out.println("\nEnter Sourcepath to copy file : ");
spath = in.readLine();
System.out.println("\nEnter DestinationPath to transfer : ");
dpath = in.readLine();
fos = new FileOutputStream(dpath);
pw.println (spath);
while ((c=br.read())!=-1)
{
fos.write((char)c);
fos.flush();
}
System.out.println("File trasfer completed:\n");
}
catch (Exception e)
{
System.out.println(e);
}
}
}
SERVER SIDE PROGRAM:
import java.net.*;
import java.io.*;
public class ftpserver
{
public static void main(String args[])
{
Socket s;
ServerSocket server;
FileInputStream fis;
BufferedReader br;
PrintWriter pw;
String filename;
int c;
try
{
server = new ServerSocket(1111);
System.out.println("Server waitfor for connection:\n");
s = server.accept();
System.out.println("Connection established:\n");
br = new BufferedReader(new InputStreamReader(s.getInputStream()));
pw = new PrintWriter(s.getOutputStream());
filename = br.readLine();
fis = new FileInputStream(filename);
while ((c=fis.read())!=-1)
{
pw.print((char)c);
pw.flush();
}
System.out.println(filename + " copied to destnation");
s.close();
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Output:
TELNET
In the very earliest days of internetworking, one of the
most
important problems that computer scientists needed to solve was
how to allow someone operating one computer to access and use
another as if he or she were connected to it locally. The protocol
created to meet this need was called Telnet, and the effort to develop
it was tied closely to that of the Internet and TCP/IP as a whole.
Telnet (teletype network) is a network protocol used on the
Internet or local area networks to provide a bidirectional
interactive communications facility. Typically, telnet provides
access to a command-line interface on a remote host via a
virtual terminal connection which consists of an 8-bit byte
oriented data connection over the Transmission Control
Protocol.
Program:
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
public class telnet extends WindowAdapter implements ActionListener,KeyListener {
public static Frame telFrame;
public static Socket s;
public static BufferedReader br = null;
public static PrintWriter pw = null;
public static telnet tnet;
public static MenuBar mbar;
public static Menu connectMenu;
public static Menu helpMenu;
public static MenuItem connect,disconnect,exit,help;
public static TextArea msgArea;
public static TextField statusArea;
public static String command = "";
public static void main(String args[])
{
telFrame = new Frame("Telnet");
msgArea = new TextArea();
statusArea = new TextField();
Panel p = new Panel();
p.setLayout(new BorderLayout());
mbar = new MenuBar();
connectMenu = new Menu("Connect");
connectMenu.add(connect = new MenuItem("Connect"));
connectMenu.add(disconnect = new MenuItem("Disconnect"));
connectMenu.add(exit = new MenuItem("Exit"));
mbar.add(connectMenu);
helpMenu = new Menu("Help");
helpMenu.add(help = new MenuItem("help"));
//helpMenu.add(more = new MenuItem("More.."));
mbar.add(helpMenu);
connect.addActionListener(new telnet());
disconnect.addActionListener(new telnet());
exit.addActionListener(new telnet());
help.addActionListener(new telnet());
//more.addActionListener(new Telnet());
msgArea.addKeyListener(new telnet());
p.add(msgArea,BorderLayout.CENTER);
p.add(statusArea,BorderLayout.SOUTH);
telFrame.setSize(450,350);
telFrame.setMenuBar(mbar);
telFrame.add(p);
telFrame.setVisible(true);
telFrame.addWindowListener(new telnet());
}
public void windowClosing(WindowEvent we) {
telFrame.setVisible(false);
System.exit(0);
}
public void keyPressed(KeyEvent ke) {}
public void keyReleased(KeyEvent ke) {}
public void keyTyped(KeyEvent ke) {
if(ke.getKeyChar() == KeyEvent.VK_ENTER) {
System.out.println(command);
pw.println(command);
command = "";
}
else if(ke.getKeyChar() != KeyEvent.VK_SHIFT)
command = command + ke.getKeyChar();
}
public void actionPerformed(ActionEvent ae) {
String str = ae.getActionCommand();
if(str.equals("Exit"))
System.exit(0);
if(str.equals("Connect"))
new ConnectFrame();
else if(str.equals("Disconnect")) {
if(!(s==null)) {
System.out.println("in disconnecting...");
System.out.println("Connection terminated");
statusArea.setText("Connection terminated");
try {
s.close();
s = null;
}
catch(Exception e) {
System.out.println("closing socket.");
}
}
}
else {
new HelpFrame();
}
}
public void makeConnection() {
try {
s = new
Socket(ConnectFrame.host.getText().trim(),Integer.parseInt(ConnectFrame.p
ort.getText().trim()));
br = new BufferedReader(new InputStreamReader(s.getInputStream()));
pw = new PrintWriter(s.getOutputStream(),true);
statusArea.setText("Connection Established");
new ReadThrd(msgArea,statusArea,br);
}
catch(Exception e) {
System.out.println(e);
statusArea.setText("Connection Failed");
}
}
}
class ReadThrd extends Thread {
TextArea msgArea;
TextField statusArea;
BufferedReader br;
ReadThrd(TextArea msgArea,TextField statusArea,BufferedReader br) {
super("reading data thread");
this.msgArea = msgArea;
this.statusArea = statusArea;
this.br = br;
start();
}
public void run() {
try {
int off = 0;
while(true) {
String reply = br.readLine();
if(reply == null) {
msgArea.append("\n\n--------The remote host is not
responding--------\n\n");
break;
}
msgArea.append(reply+"\n");
}
}
catch(Exception e) {
System.out.println(e);
}
}
}
class ConnectFrame extends WindowAdapter implements ActionListener {
Frame conFrame;
public static TextField host,port;
Button connect,cancel;
public ConnectFrame() {
conFrame = new Frame("Connecting....");
host = new TextField(10);
port = new TextField(10);
connect = new Button("Connect");
cancel = new Button("Cancel");
Panel p1 = new Panel();
p1.add(new Label("Remote Host : "));
p1.add(host);
Panel p2 = new Panel();
p2.add(new Label("Port Number : "));
p2.add(port);
Panel p3 = new Panel();
p3.add(connect);
p3.add(cancel);
Panel p = new Panel();
p.setLayout(new GridLayout(3,1));
p.add(p1);
p.add(p2);
p.add(p3);
connect.addActionListener(this);
cancel.addActionListener(this);
conFrame.setSize(250,200);
conFrame.add(p);
conFrame.setVisible(true);
conFrame.addWindowListener(this);
}
public void actionPerformed(ActionEvent ae) {
telnet tnet = new telnet();
String str = ae.getActionCommand();
if(str.equals("Cancel"))
conFrame.setVisible(false);
else if(str.equals("Connect")) {
conFrame.setVisible(false);
tnet.makeConnection();
}
}
public void windowClosing(WindowEvent we) {
conFrame.setVisible(false);
}
}
class HelpFrame extends WindowAdapter
{
Frame helpFrame;
public HelpFrame()
{
helpFrame = new Frame("Telnet Help");
TextArea helpTxt = new TextArea();
helpTxt.setEditable(false);
helpTxt.setText("Telnet help");
helpFrame.add(helpTxt);
helpFrame.setSize(300,400);
helpFrame.setVisible(true);
helpFrame.addWindowListener(this);
}
public void windowClosing(WindowEvent we)
{
helpFrame.setVisible(false);
}
}
OUTPUT
TRIVIAL FILE TRANSFER PROTOCOL
WHAT IS TFTP

Trivial File Transfer Protocol (TFTP) is a file
transfer protocol, with the functionality of a very
basic form of File Transfer Protocol (FTP)

It was first defined in 1980.
INFORMATION ABOUT TFTP
It is a simple protocol to transfer files. It has
been implemented on top of the User
Datagram Protocol (UDP) using port number
69.
 TFTP only reads and writes files (or mail)
from/to a remote server. It cannot list
directories, and currently has no provisions for
user authentication.

TFTP supports three different transfer modes,
"netascii", "octet" and "mail", with the first two
corresponding to the "ASCII" and "image"
(binary) modes of the FTP protocol, and the
third was made obsolete by RFC 1350.
 TFTP is based in part on the earlier protocol
EFTP, which was part of the PUP protocol suite.

USES

TFTP is used to read files from, or write files to,
a remote server.

Due to the lack of security, it is dangerous over
the open Internet. Thus, TFTP is generally only
used on private, local networks.
LIMITS
TFTP cannot list directory contents.
 TFTP has no authentication or encryption
mechanisms.
 TFTP allows big data packets which may burst
and cause delay in transmission.
 TFTP cannot download files larger than 1
Terabyte.


Socket Programming:
A socket is one end-point of a twoway 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. The java.net package
provides two classes--Socket and Server
Socket--that implement the client side of the
connection and the server side of the
connection, respectively.

File Transfer Protocol:
FTP is used to transfer files between computers on a
network. You can use FTP to exchange files between
computer accounts, transfer files between an account and
a desktop computer.

Trivial File Transfer Protocol:
The Trivial File Transfer Protocol (TFTP) allows a local host
to obtain files from a remote host but does not provide
reliability or security. It uses the fundamental packet
delivery services offered by UDP.
DIFFERENCE BETWEEN FTP AND TFTP:
FTP provides minimal
security through user
logins
 FTP provides a reliable
service through its use of
TCP
 FTP uses two connections
1.Data transfer
2. Control information
FTP uses plain text channel


TFTP does not use logins

TFTP does not since it uses
UDP

TFTP uses one connection
(stop and wait)

Datagram packet:
Datagram packets are used to
implement a connectionless packet delivery
service. Each message is routed from one
machine to another based solely on information
contained within that packet. Multiple packets
sent from one machine to another might be
routed differently, and might arrive in any order.
Packet delivery is not guaranteed.
InputStreamReader:
An InputStreamReader is a bridge from
byte streams to character streams: It reads
bytes and decodes them into characters using a
specified charset
SERVER SIDE PROGRAM:
import java.io.*;
import java.net.*;
import java.lang.*;
public class tftps
{
public static void main(String args[]) throws Exception
{
DatagramSocket ds=new DatagramSocket(1500);
byte s[]=new byte[1024];
DatagramPacket dp=new DatagramPacket(s,1024);
ds.receive(dp);
String data=new String(dp.getData(),0,dp.getLength());
int count=0;
System.out.println("ENTER THE FILE NAME TO TRANFER:" +data);
FileInputStream fs=new FileInputStream (data);
while(fs.available()!=0)
{
if(fs.available()<1024)
count=fs.available();
);
else
count=1024;
s=new byte[count];
fs.read(s
dp=new DatagramPacket(s,s.length,InetAddress.getLocalHost(),1501);
ds.send(dp);
}
fs.close();
s=new byte[3];
s="***".getBytes();
ds.send(newDatagramPacket(s,s.length,InetAddress.getLocalHost(),1501));
ds.close();
}
}
CLIENT SIDE PROGRAM:
import java.io.*;
import java.net.*;
import java.lang.*;
public class tftpc
{
public static void main(String args[]) throws Exception
{
DatagramSocket ds=new DatagramSocket(1501);
BufferedReader input=newBufferedReader(new
InputStreamReader(System.in));
System.out.println("ENTER THE FILE NAME TO SAVE:");
String file=input.readLine();
FileOutputStream fos=new FileOutputStream(file);
System.out.println("ENTER THE FILE NAME TO TRANFER:");
file=input.readLine();
byte s[]=new byte[file.length()];
s=file.getBytes();
String data=null;
ds.send(new
DatagramPacket(s,s.length,InetAddress.getLocalHost(),1500));
while(true)
{
s=new byte[1024];
DatagramPacket dp=new DatagramPacket(s,1024);
ds.receive(dp);
data=new String(dp.getData(),0,dp.getLength());
if(data.equals("***"))
break;
fos.write(data.getBytes());
}
fos.close();
ds.close();
}
}
Server side output:
Client side output:
HTTP
Hyper Text Transfer protocol
Client/Server:
•A server is any thing that has some resource that can be shared.
1. Compute servers
2. Print server
3. Disk servers
4. Web servers
•
A client is simply any other entity that wants to gain access to a
particular server.
INETADDRESS
This class is used to encapsulate numerical IP address and
domain name for that address
•This class has no visible constructors so to create
InetAddress object we have to use one of the
available factory methods.
•Factory methods are static methods in a class return
an instance of that class
•static InetAddress getLocalHost() throws UnknownHostException
•static InetAddress getByName(String hostName)
throws UnknownHostException
•static InetAddress[] getAllByName(String hostName)
throws UnknownHostException
InetAddress example
import java.net.*;
class InetAddressTest
{
public static void main(String args[]) throws UnknownHostException
{
InetAddress Address=InetAddress.getLocalHost();
System.out.println(Address);
Address=InetAddress.getByName("yahoo.com");
System.out.println(Address);
InetAddress sw[]=InetAddress.getAllByName("www.nba.com");
for(int i=0;i<sw.length;i++)
System.out.println(sw[i]);
}
}
HTTP Server side program:
import java.io.*;
import java.net.*;
import java.lang.*;
public class https
{
public static void main(String args[]) throws Exception
{
ServerSocket ssoc=new ServerSocket(1111);
System.out.println("Server waits for client:\n");
Socket so=ssoc.accept();
System.out.println("client connected to Server :\n");
BufferedReader br=new BufferedReader(new
InputStreamReader(so.getInputStream()));
PrintWriter pw=new PrintWriter(so.getOutputStream(),true);
BufferedReader in=new BufferedReader(new
InputStreamReader(System.in));
int ch;
do
{
ch=Integer.parseInt(br.readLine());
String file;
byte line[]=null;
File f;
switch(ch)
{
case 1: System.out.println("1.head");
file=br.readLine();
f=new File(file);
int index=file.lastIndexOf(".");
String type=file.substring(index+1);
pw.println(type);
long length=f.length();
pw.println(length);
break;
case 2: System.out.println("2.post");
file=br.readLine();
System.out.println("message from client:\n");
System.out.println(file);
break;
case 3: System.out.println("3.get");
file=br.readLine();
FileInputStream fs=new FileInputStream(file);
while(fs.available()!=0)
{
if(fs.available()<1024)
line=new byte[fs.available()];
else
line=new byte[1024];
fs.read(line);
file=new String(line);
pw.println(file);
}
pw.println("***");
fs.close();
break;
case 4:
System.out.println("4.delete");
file=br.readLine();
f=new File(file);
f.delete();
break;
default: System.out.println("5.exit");
System.exit(0);
}
}
while(ch<=4);
so.close();
ssoc.close();
}
}
HTTP Server side program:
import java.io.*;
import java.net.*;
import java.lang.*;
public class httpc
{
public static void main(String args[]) throws Exception
{
Socket soc=new Socket("localhost",1111);
BufferedReader br=new BufferedReader(new
InputStreamReader(soc.getInputStream()));
PrintWriter pw=new PrintWriter(soc.getOutputStream(),true);
BufferedReader in=new BufferedReader(new
InputStreamReader(System.in));
System.out.println("server is connected:\n");
int ch;
do
{
System.out.println("COMMANDS");
System.out.println("\n 1.head \n 2.post \n 3.get \n4.delete\n 5.exit");
System.out.println("ENTER UR CHOICE:");
ch=Integer.parseInt(in.readLine());
byte line[]=null;
String file;
switch(ch)
{
case 1:pw.println("1");
file=in.readLine();
pw.println(file);
String type=br.readLine();
String length=br.readLine();
System.out.println("FILE:"+file+"\nTYPE:"+type+"\nLEN
GTH:"+length);
break;
case 2: pw.println("2");
System.out.println("enter text to post");
file=in.readLine();
pw.println(file);
System.out.println("text is posted at server");
break;
case 3:pw.println("3");
System.out.println("enter file name to get");
file=in.readLine();
pw.println(file);
System.out.println("enter file name to save:");
file=in.readLine();
FileOutputStream fs=new FileOutputStream(file);
while(true)
{
String s=br.readLine();
if(s.equals("***"))
break;
int count=s.length();
if(count<1024)
line=new byte[1024];
line=s.getBytes();
fs.write(line);
}
fs.close();
System.out.println("\n file successfully tranfered:");
break;
case 4: pw.println("4");
System.out.println("enter the file to delete:");
file=in.readLine();
pw.println(file);
System.out.println("given file deleted:");
break;
default: pw.println("5");
System.exit(0);
}
}
while(ch<=4);
soc.close();
}
}
Clint side Output window: