Implementation of Tcp socket
Client Side Programming
Establish a Socket
Connection
To connect to other machine we need
a socket connection. A socket connection means the two machines have
information about each other’s network location (IP Address) and TCP port.The
java.net.Socket class represents a Socket. To open a socket:
Socket
socket = new Socket(“127.0.0.1”, 5000)
·
First argument – IP address of Server. ( 127.0.0.1 is the IP
address of localhost, where code will run on single stand-alone machine).
·
Second argument – TCP Port. (Just a number representing which application
to run on a server. For example, HTTP runs on port 80. Port number can be
from 0 to 65535)
To communicate over a socket
connection, streams are used to both input and output the data.
Closing
the connection
The socket connection is closed
explicitly once the message to server is sent.
In the program, Client keeps
reading input from user and sends to the server until “Over” is typed.
Java Implementation
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// A Java program for a Client
import java.net.*;
import java.io.*;
public class Client
{
//
initialize socket and input output streams
private
Socket
socket =
null;
private
DataInputStream input = null;
private
DataOutputStream out = null;
//
constructor to put ip address and port
public
Client(String address, int port)
{
//
establish a connection
try
{
socket
= new Socket(address, port);
System.out.println("Connected");
//
takes input from terminal
input
= new DataInputStream(System.in);
//
sends output to the socket
out
= new DataOutputStream(socket.getOutputStream());
}
catch(UnknownHostException
u)
{
System.out.println(u);
}
catch(IOException
i)
{
System.out.println(i);
}
//
string to read message from input
String
line = "";
//
keep reading until "Over" is input
while
(!line.equals("Over"))
{
try
{
line
= input.readLine();
out.writeUTF(line);
}
catch(IOException
i)
{
System.out.println(i);
}
}
//
close the connection
try
{
input.close();
out.close();
socket.close();
}
catch(IOException
i)
{
System.out.println(i);
}
}
public
static void main(String args[])
{
Client
client = new Client("127.0.0.1", 5000);
}
}
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Server Programming
Establish a Socket
Connection
To write a server application
two sockets are needed.
·
A ServerSocket which waits for the client
requests (when a client makes a new Socket())
·
A plain old Socket socket to use for
communication with the client.
Communication
getOutputStream() method is used to
send the output through the socket.
Close the Connection
After finishing, it is
important to close the connection by closing the socket as well as input/output
streams.
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// A Java program for a Server
import java.net.*;
import java.io.*;
public class Server
{
//initialize
socket and input stream
private
Socket
socket = null;
private
ServerSocket server = null;
private
DataInputStream in = null;
//
constructor with port
public
Server(int port)
{
//
starts server and waits for a connection
try
{
server
= new ServerSocket(port);
System.out.println("Server
started");
System.out.println("Waiting
for a client ...");
socket
= server.accept();
System.out.println("Client
accepted");
//
takes input from the client socket
in
= new DataInputStream(
new
BufferedInputStream(socket.getInputStream()));
String
line = "";
//
reads message from client until "Over" is sent
while
(!line.equals("Over"))
{
try
{
line
= in.readUTF();
System.out.println(line);
}
catch(IOException
i)
{
System.out.println(i);
}
}
System.out.println("Closing
connection");
//
close connection
socket.close();
in.close();
}
catch(IOException
i)
{
System.out.println(i);
}
}
public
static void main(String args[])
{
Server
server = new Server(5000);
}
}
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1. First run the Server application
as ,
$ java Server
Server started
Waiting for a client …
Waiting for a client …
2. Then run the Client application
on another terminal as,
$ java Client
It will show – Connected and the
server accepts the client and shows,
Client accepted
3. Then you can start typing
messages in the Client window. Here is a sample input to the Client
Hello
I made my first socket connection
Over
Which the Server simultaneously
receives and shows,
Hello
I made my first socket connection
Over
Closing connection
Notice that sending “Over” closes
the connection between the Client and the Server just like said before.
