Java Network Classes Part2

 

Java Networking Tutorial

 

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HttpURLConnection class

 

It is the subclass URLConnection
Provides support for HTTP connctions on port 80.
to open a connection we use openConnection on a URL object
and must cast the result to HttpURLConnection.

methods
 
getRequestMethod()
getResponseCode()
getResponseMessage()
getHeaderFields()


 

import java.net.*;
import java.io.*;

public class HttpURLDemo {

  public static void main(String[] args) throws IOException {
  
   URL hp = new URL("http://www.google.com");
    HttURLConnection hpCon = (HttpURLDemo) hp.openConnection();

   System.out.println("Request method is"+hpCon.getRequestMethod());
   System.out.println("Response code is"+hpCon.getResponseCode());
   System.out.println("Requst method is"+hpCon.getResponseMessage());
   Map<String>,List<String> hdrMap=hpCon.getHeaderFields());
   Set<String> hdrField =   hdrMap.keySet();
  
   System.out.println("Here is the header:");
   for(String k:hdrField){
   System.out.println("Key:"+k+"Value:"+hdrMap.get(k));
}
}
}

URI (UniformResourceIdentifier) class

It is a part of URL.

Similar to URLs. URL contains the URIs. It is a standard way of identifing resource.

 TCP/IP ServerSockets

Client and server communicates using 2 classes.

1. Socket → used by client, to communicate with server.

2. ServerSocket → listens for either local/remote client program to connect to them. it has a method called accept().

GET any URL using SOCKET connection from a JAVA Program

 
This Java example  shows how to GET content from any URL using SOCKET connection

from a Java porgram.

import java.net.*; 
import java.io.*; 
import java.util.*;
 
public class Socketget { 

public static void main(String[] args) throws Exception { 

try { 

Socket socket = new Socket("www.oracle.com",80); 

PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()))); 

out.println("GET /index.html HTTP/1.0"); 
out.println(); 
out.flush(); 

BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream())); 

String inputLine; 
int count = 0; 

while ((inputLine = in.readLine()) != null) { 
count++; 
System.out.println(count); 
System.out.print(inputLine); 
} 

in.close(); 
System.out.println("PRINTING HERE!!!"); 
} catch (Exception e) { 
e.printStackTrace(); 
} 
} 
} 

 

Find WHOIS information of any domain from a JAVA Program

//Demonstrate Socket class

import java.net.*;
import java.io.*;

class Whois{
 public static void main(String args[]) throws Exception{
 	int c;
 	Socket s = new Socket("whois.oracle.com",43);
 	InputStream in = s.getInputStream();
 	OutputStream out = s.getOutputStream();
 	String str=(args.length==0?"oracle.com": args[0]+"\n";
 	byte buf[] = str.getBytes();
 	out.write(buf);
 	while((c=in.read())!= -1){
 		System.out.println((char)c);
 		}
 		s.close();
}
}
 

 

 

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