Datagram Client in Java

// Datagram Client or UDP client
// purpose of this example is to provide a fare idea about the working of UDP client server
// this client example works with server example and link to server example is given at the end of this code
// example works on the concept of UDP protocol (simple transmission model without implicit handshaking)

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

public class Client {
   
    public static void main(String[] args) {
     
      DatagramSocket clientSkt = null;
      InetAddress IPAdd = null;
      String text =null;
      DatagramPacket receivePkt= null;
      BufferedReader inFromUser =
         new BufferedReader(new InputStreamReader(System.in));
      try{
      clientSkt = new DatagramSocket();
      IPAdd = InetAddress.getByName("localhost");
      }
      catch(SocketException exp){
          System.out.println(exp);
      }
      catch(UnknownHostException exp){
          System.out.println(exp);
      }     
      byte[] sendData = new byte[1024];
      byte[] receiveData = new byte[1024];
      try{
      text = inFromUser.readLine();
      sendData = text.getBytes();
      DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAdd, 3030);
      clientSkt.send(sendPacket);
      receivePkt = new DatagramPacket(receiveData, receiveData.length);
      clientSkt.receive(receivePkt);
      }
      catch(IOException exp){
          System.out.println(exp);
      }
      String modifiedSentence = new String(receivePkt.getData());
      System.out.println("FROM SERVER:" + modifiedSentence);
      clientSkt.close();
    }
}

Datagram Server Source

Datagram Server in Java

// Datagram Server or UDP server
// purpose of this example is to provide a fare idea about the working of UDP client server
// this server example works with client example and link to the client example is given at the end of this code
// example works on the concept of UDP protocol (simple transmission model without implicit handshaking)


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

public class Server {

  
    public static void main(String[] args) {
       
        DatagramSocket serverSkt= null;
        try{
            serverSkt = new DatagramSocket(3030);
        }
        catch(SocketException exp)
        {
            System.out.println(exp);
        }
        byte[] receiveData = new byte[1024];
        byte[] sendData = new byte[1024];
        while(true)
          {
            DatagramPacket receivePkt = new DatagramPacket(receiveData, receiveData.length);
            try{
                serverSkt.receive(receivePkt);
            }
            catch(IOException exp)
            {
                System.out.println(exp);
            }
            String sentence = new String( receivePkt.getData());
            System.out.println("RECEIVED: " + sentence);
            InetAddress IPAddress = receivePkt.getAddress();
            int port = receivePkt.getPort();
            String capitalizedSentence = sentence.toUpperCase();
            sendData = capitalizedSentence.getBytes();
            DatagramPacket sendPkt =
            new DatagramPacket(sendData, sendData.length, IPAddress, port);
            try{
            serverSkt.send(sendPkt);
            }
            catch(IOException exp)
            {
                System.out.println(exp);
            }  
        }
      }
       
    }

Datagram Client Source

Get Your PC's IP Address in Java

//this example returns IP address of your PC

import java.net.*;

public class tellMyIP {

public static void main(String[] args) {
 InetAddress localHostIP= null;
   //creates instance of InetAddress
  try{
  localHostIP=InetAddress.getLocalHost();
  //initializes localHostIP
  System.out.println("IP ADDRESS OF MY PC IS = "+localHostIP.getHostAddress());
  //gets IP address and prints it
  }catch (Exception exception){
  System.out.println("Something that went wrong is :"+exception.getMessage());
  }
   }
}

Send email in Java with attachment

//javax.mail API is required to work with this code
//send email in Java from Gmail account with attachments

import java.util.Properties;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class MailWithAttachment
{
public static void main(String args[]) throws Exception
{
    String host = "smtp.gmail.com";//host name
    String from = "abc@gmail.com";//sender id
    String to = "xyz@yahoo.com";//reciever id
    String pass = "***";//sender's password
    String fileAttachment = "test.txt";//file name for attachment
    //system properties
    Properties prop = System.getProperties();
    // Setup mail server properties
    prop.put("mail.smtp.gmail", host);
    prop.put("mail.smtp.starttls.enable", "true");
    prop.put("mail.smtp.host", host);
    prop.put("mail.smtp.user", from);
    prop.put("mail.smtp.password", pass);
    prop.put("mail.smtp.port", "587");
    prop.put("mail.smtp.auth", "true");
    //session
    Session session = Session.getInstance(prop, null);
    // Define message
    MimeMessage message = new MimeMessage(session);
    message.setFrom(new InternetAddress(from));
    message.addRecipient(Message.RecipientType.TO,new InternetAddress(to));
    message.setSubject("Hello Java Mail Attachment");
    // create the message part
    MimeBodyPart messageBodyPart = new MimeBodyPart();
    //message body
    messageBodyPart.setText("Hi");
    Multipart multipart = new MimeMultipart();
    multipart.addBodyPart(messageBodyPart);
    //attachment
    messageBodyPart = new MimeBodyPart();
    DataSource source = new FileDataSource(fileAttachment);
    messageBodyPart.setDataHandler(new DataHandler(source));
    messageBodyPart.setFileName(fileAttachment);
    multipart.addBodyPart(messageBodyPart);
    message.setContent(multipart);
    //send message to reciever
    Transport transport = session.getTransport("smtp");
    transport.connect(host, from, pass);
    transport.sendMessage(message, message.getAllRecipients());
    transport.close();
}
}

Database Connctions in Java

//sun.jdbc.odbc.JdbcOdbc
// this example Works with MS Access. can be changed acc. any other database
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class dbConnections
{
public static void main(String args[])
{
     try{ 
      Class.forName("sun.jdbc.odbc.JdbcOdbc");  //load DB drivers
      Connection con=DriverManager.getConnection("jdbc:odbc:DBName",username,pwd);
      //create db connections
      Statement stmt = con.createStatement(); // creates statement for db access
      String query = "SELECT * FROM Job"; // sql query
      ResultSet rs = stmt.executeQuery(query);
      //execute sql query and stores the result in the result set rs
      while( rs.next() ) {
       System.out.println("Job  "+rs.getString("Job_Id"));
      }
      rs.close(); //close resultset
      stmt.close(); // close statement
      con.close();  // close connection  
     }
    catch(SQLException e)
    {
     System.out.println(e);
    }
    catch(ClassNotFoundException e)
    {
     System.out.println(e);
   }
}
}

Read emails from Gmail Account

// this code reads emails from a gmail account
// to work with this code you will need javax.mail API

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.FileWriter;
import java.io.InputStream;
import java.security.*;
import java.util.Properties;
import javax.mail.*;

public class ReadMail {
  public static void main(String args[]) throws IOException {
         Properties properties = System.getProperties();
         properties.setProperty("mail.store.protocol", "imaps");
             try {
                 Session session = Session.getDefaultInstance(properties, null);
                 //create session instance
                 Store store = session.getStore("imaps");//create store instance
                 store.connect("pop.gmail.com", "abc@gmail.com", "****");
                 //set your user_name and password
                 System.out.println(store);
                 Folder inbox = store.getFolder("inbox");
                 //set folder from where u wants to read mails
                 inbox.open(Folder.READ_ONLY);//set access type of Inbox
                 Message messages[] = inbox.getMessages();// gets inbox messages
                 for (int i = 0; i < messages.length; i++) {
                System.out.println("------------ Message " + (i + 1) + " ------------");
                System.out.println("SentDate : " + messages[i].getSentDate()); //print sent date
                System.out.println("From : " + messages[i].getFrom()[0]); //print email id of sender
                System.out.println("Sub : " + messages[i].getSubject()); //print subject of email
                try
                {
                      Multipart mulpart = (Multipart) messages[i].getContent();
                      int count = mulpart.getCount();
                      for (int j = 0; j+1 < count; j++)
                     {
                          storePart(mulpart.getBodyPart(j));
                     }
                }
                catch (Exception ex)
                {
                     System.out.println("Exception arise at get Content");
                     ex.printStackTrace();
                }
           }
           store.close();
      }
catch (Exception e) {
System.out.println(e); 
} 
}
  public static void storePart(Part part) throws Exception
     {   
          InputStream input = part.getInputStream();
          if (!(input instanceof BufferedInputStream))
         {
              input = new BufferedInputStream(input);
          }
          int i;
         System.out.println("msg : ");
          while ((i = input.read()) != -1)
         {
         System.out.write(i);
         }
     }
}

Send email using javax.mail source

Telnet Client

Telnet Client
//this code connects to the telnet server and receives data whenever command "1" is entered
import java.net.*;
import java.io.*;

class TelnetClient
{
    public static void main(String args[]) throws Exception
    {
        //Create object of Socket
        Socket soc=new Socket("localhost",8088);
        String Command;
        //Create object of Input Stream to read from socket
        DataInputStream din=new DataInputStream(soc.getInputStream());   
        //Create object of Output Stream  to write on socket
        DataOutputStream dout=new DataOutputStream(soc.getOutputStream());
        // Object of Buffered Reader to read command from terminal
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Welcome to Telnet Client");
        System.out.println("< Telnet Prompt >");
        Command=br.readLine();//reads the command
        dout.writeUTF(Command);//sends command to server
        System.out.println(din.readLine()); //gets the response of server       
        soc.close();  //close port 
        din.close();  //close input stream      
        dout.close(); //close output stream     
        br.close();  //close buffered Reader   
    }
}

Telnet Server Source