Writing UDP Clients and Servers

Writing UDP Clients and Servers

o write UDP clients and servers, you have to use the DatagramSocket class. UDP is a connectionless protocol, so a UDP server doesn’t have to perform an accept() operation the way a TCP server using ServerSocket has to. Unlike Socket, you do not communicate by writing to an OutputStream and reading from an InputStream. Rather, you send datagrams using the DatagramPacket class. Each packet you receive must have a predefined size and byte buffer. Each packet you send must also have a destination address and port number associated with it. The easiest way to give you the feel for how it all works is to write a sample program. The following program connects to the UDP daytime service on a host and prints the result. The key item to pay attention to is the difference between a send and receive packet. Send packets contain address information, receive packets don’t. The raw byte data in a packet can be accessed with getData() and the length of the actual data in the byte array (as opposed to the length of the array itself), can be obtained with getLength().

import java.io.*;import java.net.*;public class Daytime {  public static final int DAYTIME_PORT = 13;  public static final String getTime(String hostname) throws IOException {    InetAddress host;    DatagramSocket socket = new DatagramSocket();    byte[] dummyData = new byte[1];    byte[] timeData  = new byte[256];    DatagramPacket sendPacket, receivePacket;    host = InetAddress.getByName(hostname);    sendPacket =       new DatagramPacket(dummyData, dummyData.length, host, DAYTIME_PORT);    receivePacket = new DatagramPacket(timeData, timeData.length);    socket.send(sendPacket);    socket.receive(receivePacket);    return      new String(receivePacket.getData(), 0, receivePacket.getLength());  }  public static void main(String[] args) {    String server = "tock.usno.navy.mil";    if(args.length == 1)      server = args[0];    else if(args.length > 1) {      System.err.println("Usage: Daytime [hostname]");      return;    }    try {      // Time should include newline, so we don't use println().      System.out.print(getTime(server));      System.out.flush();     } catch(IOException e) {      e.printStackTrace();      return;    }  }                   }
Share the Post:
Heading photo, Metadata.

What is Metadata?

What is metadata? Well, It’s an odd concept to wrap your head around. Metadata is essentially the secondary layer of data that tracks details about the “regular” data. The regular

XDR solutions

The Benefits of Using XDR Solutions

Cybercriminals constantly adapt their strategies, developing newer, more powerful, and intelligent ways to attack your network. Since security professionals must innovate as well, more conventional endpoint detection solutions have evolved

AI is revolutionizing fraud detection

How AI is Revolutionizing Fraud Detection

Artificial intelligence – commonly known as AI – means a form of technology with multiple uses. As a result, it has become extremely valuable to a number of businesses across

AI innovation

Companies Leading AI Innovation in 2023

Artificial intelligence (AI) has been transforming industries and revolutionizing business operations. AI’s potential to enhance efficiency and productivity has become crucial to many businesses. As we move into 2023, several

data fivetran pricing

Fivetran Pricing Explained

One of the biggest trends of the 21st century is the massive surge in analytics. Analytics is the process of utilizing data to drive future decision-making. With so much of

kubernetes logging

Kubernetes Logging: What You Need to Know

Kubernetes from Google is one of the most popular open-source and free container management solutions made to make managing and deploying applications easier. It has a solid architecture that makes