Overview
- Java Networking is a concept of connecting two or more computing devices togetherso that we can share resources.
- Java socket programming provides facility to share data between different computingdevices.
Java Networking
- The java.net package supports two protocols,
- TCP: Transmission Control Protocol provides reliable communication between thesender and receiver. TCP is used along with the Internet Protocol referred as TCP/IP.
- UDP: User Datagram Protocol provides a connection-less protocol service byallowing packet of data to be transferred along two or more nodes.
Java Networking Terminology
- The widely used Java networking terminologies are given below:
- IP Address
- Protocol
- Port Number
- MAC Address
- Connection-oriented and connection-less protocol
- Socket
IP Address
- IP address is a unique number assigned to a node of a network e.g. 192.168.0.1
- It is composed of octets that range from 0 to 255.
- It is a logical address that can be changed.
Protocol
- A protocol is a set of rules basically that is followed for communication.
- For example:
- TCP
- FTP
- Telnet
- SMTP
- POP etc.
Port Number
- The port number is used to uniquely identify different applications.
- It acts as a communication endpoint between applications.
- The port number is associated with the IP address for communication between twoapplications.
MAC Address
- MAC (Media Access Control) address is a unique identifier of NIC (Network InterfaceController).
- A network node can have multiple NIC but each with unique MAC address.
- For example, an ethernet card may have a MAC address of 00:0d:83::b1:c0:8e.
Connection-oriented and Connection-less Protocol
- In connection-oriented protocol, acknowledgement is sent by the receiver. So, it isreliable but slow.
- The example of connection-oriented protocol is TCP.
- But, in connection-less protocol, acknowledgement is not sent by the receiver. So, it isnot reliable but fast.
- The example of connection-less protocol is UDP.
Socket
- A socket is an endpoint between two-way communications.
- Visit next page for Java socket programming.
java.net Package
- The java.net package can be divided into two sections:
- A Low-Level API: It deals with the abstractions of addresses High-Level networkingidentifiers, Sockets High-Level bidirectional data communication mechanism andInterfaces i.e. network interfaces.
- A High-Level API: It deals with the abstraction of URIs i.e. Universal ResourceIdentifier, URLs i.e. Universal Resource Locator, and Connections i.e. connections tothe resource pointed by URLs.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
/*
* this is a simple tcp server
* this server will receive a message from a client upon connection
* then it will display the message to output
*/
public class TCPServer {
public static void main(String[] args) {
// start the server for listening
try (ServerSocket server = new ServerSocket(8080)) {
// if server is up and running
System.out.println("Server is listening....");
// accept incoming client request
Socket socket = server.accept();
PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
BufferedReader reader =
new BufferedReader(new InputStreamReader(socket.getInputStream()));
// read message from client
String msg = reader.readLine();
System.out.println("Received: " + msg);
// write (send) message to client
writer.println("Hello from server!");
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
/*
* this is a simple tcp client
* this client will try to connect to the simple server and send message
*/
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class TCPClient {
public static void main(String[] args) {
// try connect to server
try (Socket socket = new Socket("localhost", 8080)) {
// if successfully connected
System.out.println("Connected!");
PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
BufferedReader reader =
new BufferedReader(new InputStreamReader(socket.getInputStream()));
// send message to server
writer.println("Hello from client!");
// read message from server
String msg = reader.readLine();
System.out.println("Response: " + msg);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
