3. Basics of NetworkiNg
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
4. Network basics
Transmission Control Protocol (TCP)
- Connection-Oriented
- Reliable
TCP is a connection-based protocol that provides a reliable flow of data
between two computers.
User Datagram Protocol (UDP)
- Connectionless
- Unreliable
UDP is a protocol that sends independent packets of data, called datagrams,
from one computer to another with no guarantees about arrival.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
5. Network basics
Internet Protocol (IP)
IP is a low level protocol for delivering data from one computer
to another across the internet in packets.
IP address
uniquely identifies the computer on Internet.
DNS (Domain Name Server)
translates the host name into IP address.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
6. Understanding Ports
Data transmitted over the Internet is accompanied by addressing
information that identifies the computer and the port for which it is
destined.
The computer is identified by its 32-bit IP address, which IP uses to
deliver data to the right computer on the network.
Ports are identified by a 16-bit number, which TCP and UDP use to
deliver the data to the right application.
Port number ranges from 0 to 65536 but 0 to 1024 are reserved.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
8. Client-Server Architecture
Network Programming involves a Server and one or more
Clients.
Client attempts to establish a connection with the Server.
The server can accept or deny the connection.
Once the connection is established, Client sends requests to the
server and server responds.
The communication takes place through Sockets.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
9. Sockets
Sockets are the endpoints of logical connection between
two hosts and used to send and receive data.
Used to implement reliable, bidirectional, persistent, pointto-point, stream-based connections between hosts on the
Internet.
There are two kinds of TCP sockets in Java.
- Socket
- ServerSocket
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
10. ServerSocket
ServerSocket is for servers.
To establish a server, we need to create a ServerSocket.
ServerSocket is attached to a port where the Server listens
for the connection.
accept() method is defined in ServerSocket class which is a
blocking call that will wait for a client to initiate.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
12. Socket
The Socket class is for clients.
It is designed to connect to server sockets and initiate
protocol exchanges.
Socket(String hostName, int port)throws
UnknownHostException, IOException
Socket(InetAddress ipAddress, int port) throws
IOException
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
14. Socket Methods
connect( ) allows us to specify a new connection
isConnected( ) returns true if the socket is connected to a
server
isClosed( ) returns true if the socket is closed.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
15. InetAddress Class
InetAddress class is used to find the client’s host name and IP
address.
Example:
Socket s = new Socket(“172.19.2.250”, 8000);
Socket s = new Socket(“lpu.co.in”, 8000);
InetAddress ia = s.getInetAddress();
InetAddress ia = InetAddress.getByName(“lpu.co.in”);
Methods:
ia.getHostName();
ia.getHostAddress();
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
17. Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
18. Multiple Clients
Multiple clients can be connected to a server.
A server can serve multiple clients simultaneously.
The connection to each client is handled by one thread.
while (true)
{
Socket socket = serverSocket.accept();
Thread thread = new ThreadClass(socket);
thread.start();
}
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
20. Applet Clients
The client can be an applet that connects to the server running
on the host from which the applet is loaded.
HTML file must be located on the machine on which the server
is running.
Server’s host name can be obtained by invoking
getCodeBase().getHost() on an applet.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
21. Sending and Receiving Objects
Similar to the data of primitive types, we can send and receive
the Objects.
ObjectOutputStream and ObjectInputStream is used for
sending and receiving the objects on socket streams.
We can pass only serializable objects.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
22. Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
23. Java Mail API
JavaMail is an API that is used to compose, write and read
electronic messages.
The JavaMail API provides platform independent framework
for sending and receiving mails.
The javax.mail and javax.mail.activation packages contains the
core classes of JavaMail API.
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
24. Steps to send email using JavaMail API
Get the session object.
Compose the message
Send the message
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
25. Steps to send email using JavaMail API
1. Get the session object
The javax.mail.Session class provides two methods to get the
object of session
public static Session getDefaultInstance( Properties props)
public static Session getDefaultInstance( Properties props,
Authentication auth)
public static Session getInstance( Properties props)
public static Session getInstance( Properties props, Authentication
auth)
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
26. Steps to send email using JavaMail API
2. Compose the message
The javax.mail.Message class provides methods to compose the
message.
But it is an abstract class so its subclass
javax.mail.internet.MimeMessage class is mostly used.
public MimeMessage (Session s)
public void setFrom(Address address)
public void addRecipients(Message.RecipientType type,
String addresses)
public void setSubject( String sub)
public void setText( String msg)
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
27. Steps to send email using JavaMail API
3. Send the message
The javax.mail.Transport class provides method to send the
message.
public static void send(Message message)
public static void send(Message message, Address [] address)
Ravi Kant Sahu, Asst. Professor @ Lovely Professional University, Punjab (India)
