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Java Networking
Introduction to Java Networking:
Java Networking is a concept of connecting two or more computing devices together to share resources. Java provides a powerful networking library that allows developers to easily create network applications.
Socket Programming:
Socket programming is the fundamental technology behind Java networking. It allows for the communication between applications running on different JREs.
import java.net.*;
import java.io.*;
public class MyServer {
public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(6666);
Socket s = ss.accept();
DataInputStream dis = new DataInputStream(s.getInputStream());
String str = (String)dis.readUTF();
System.out.println("message= " + str);
ss.close();
} catch(Exception e) {
System.out.println(e);
}
}
}
Client-Side Socket:
A client-side socket is used to connect to a server and send or receive data.
import java.net.*;
import java.io.*;
public class MyClient {
public static void main(String[] args) {
try {
Socket s = new Socket("localhost", 6666);
DataOutputStream dout = new DataOutputStream(s.getOutputStream());
dout.writeUTF("Hello Server");
dout.flush();
dout.close();
s.close();
} catch(Exception e) {
System.out.println(e);
}
}
}
DatagramSocket and DatagramPacket:
These classes are used for sending and receiving datagrams, which are self-contained, independent packets of data sent over the network.
import java.net.*;
public class DatagramExample {
public static void main(String[] args) throws Exception {
DatagramSocket ds = new DatagramSocket();
String str = "Hello";
InetAddress ip = InetAddress.getByName("127.0.0.1");
DatagramPacket dp = new DatagramPacket(str.getBytes(), str.length(), ip, 3000);
ds.send(dp);
ds.close();
}
}
URL and URLConnection:
The URL class represents a Uniform Resource Locator, which is a pointer to a resource on the World Wide Web. URLConnection is a communication link between the application and a URL.
import java.net.*;
import java.io.*;
public class URLConnectionExample {
public static void main(String[] args) {
try {
URL url = new URL("http://www.example.com");
URLConnection urlcon = url.openConnection();
InputStream stream = urlcon.getInputStream();
int i;
while((i = stream.read()) != -1) {
System.out.print((char)i);
}
} catch(Exception e) {
System.out.println(e);
}
}
}
InetAddress Class:
The InetAddress class is used to represent an IP address. It can be used to resolve hostnames to IP addresses and vice versa.
import java.net.*;
public class InetAddressExample {
public static void main(String[] args) {
try {
InetAddress address = InetAddress.getByName("www.example.com");
System.out.println("IP Address: " + address.getHostAddress());
System.out.println("Host Name: " + address.getHostName());
} catch(Exception e) {
System.out.println(e);
}
}
}
Multithreaded Server:
A multithreaded server is capable of handling multiple client requests simultaneously by using threads.
import java.net.*;
import java.io.*;
public class MultiThreadedServer implements Runnable {
Socket socket;
MultiThreadedServer(Socket socket) {
this.socket = socket;
}
public void run() {
try {
DataInputStream dis = new DataInputStream(socket.getInputStream());
String str = (String)dis.readUTF();
System.out.println("message= " + str);
socket.close();
} catch(Exception e) {
System.out.println(e);
}
}
public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(6666);
while(true) {
Socket s = ss.accept();
new Thread(new MultiThreadedServer(s)).start();
}
} catch(Exception e) {
System.out.println(e);
}
}
}
HTTP Client:
Java provides an HTTP client API to send requests to web servers and receive responses.
import java.net.*;
import java.io.*;
public class HttpClientExample {
public static void main(String[] args) {
try {
URL url = new URL("http://www.example.com");
HttpURLConnection con = (HttpURLConnection)url.openConnection();
con.setRequestMethod("GET");
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer content = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
content.append(inputLine);
}
in.close();
con.disconnect();
System.out.println(content.toString());
} catch(Exception e) {
System.out.println(e);
}
}
}
Proxy Settings:
Java allows you to configure proxy settings for network connections, which can be useful for accessing resources behind a firewall.
import java.net.*;
public class ProxyExample {
public static void main(String[] args) {
try {
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("proxy.example.com", 8080));
URL url = new URL("http://www.example.com");
HttpURLConnection con = (HttpURLConnection)url.openConnection(proxy);
con.setRequestMethod("GET");
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer content = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
content.append(inputLine);
}
in.close();
con.disconnect();
System.out.println(content.toString());
} catch(Exception e) {
System.out.println(e);
}
}
}
Secure Sockets (SSL):
Java provides support for secure sockets through the use of SSL/TLS, allowing for encrypted communication over the network.
import javax.net.ssl.*;
import java.io.*;
import java.net.*;
public class SSLClient {
public static void main(String[] args) {
try {
SSLSocketFactory ssf = (SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket socket = (SSLSocket) ssf.createSocket("www.example.com", 443);
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out.write("GET / HTTP/1.1\r\n");
out.write("Host: www.example.com\r\n");
out.write("\r\n");
out.flush();
String line;
while ((line = in.readLine()) != null) {
System.out.println(line);
}
in.close();
out.close();
socket.close();
} catch (Exception e) {
System.out.println(e);
}
}
}
Conclusion:
Java networking provides a comprehensive set of tools for developing network applications. From basic socket programming to advanced HTTP and SSL connections, Java covers a wide range of networking needs.
