UDP Protocol (User Datagram Protocol)

The User Datagram Protocol (UDP) is a connectionless protocol that provides a simple, unreliable datagram service. It is part of the Internet protocol suite, commonly referred to as the TCP/IP suite.

Unlike TCP, UDP does not guarantee delivery, order, or duplicate protection of datagrams. It sends data as datagrams, which are independent packets that can travel different paths and arrive out of order, or not at all. This makes UDP suitable for applications where speed and low overhead are more critical than absolute reliability, such as streaming media, online gaming, and DNS lookups.

Key Characteristics of UDP

• Connectionless: No handshake is required before sending data.
• Unreliable: No guarantee of delivery, order, or error checking beyond basic checksums.
• Low Overhead: Minimal header information, leading to faster transmission.
• Datagram-Oriented: Data is sent in discrete packets (datagrams).
• Suitable for: Real-time applications, streaming, gaming, DNS, VoIP.

UDP vs. TCP

The primary difference between UDP and TCP lies in their reliability guarantees and overhead:

Using UDP in .NET with System.Net.Sockets.UdpClient

The UdpClient class in the System.Net.Sockets namespace provides a simple API for sending and receiving UDP datagrams.

Sending Data

To send data, you typically create a UdpClient instance, specify the remote endpoint (IP address and port), and use the Send() method.

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

public class UdpSender
{
    public static void SendMessage(string message, string ipAddress, int port)
    {
        using (UdpClient udpClient = new UdpClient())
        {
            try
            {
                byte[] messageBytes = Encoding.UTF8.GetBytes(message);
                IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Parse(ipAddress), port);

                udpClient.Send(messageBytes, messageBytes.Length, remoteEndPoint);
                Console.WriteLine($"Sent message: '{message}' to {remoteEndPoint}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error sending message: {ex.Message}");
            }
        }
    }

    public static void Main(string[] args)
    {
        // Example usage:
        // SendMessage("Hello UDP!", "127.0.0.1", 11000);
    }
}
            

Receiving Data

To receive data, you bind the UdpClient to a local endpoint and then use the Receive() method. This method blocks until a datagram is received.

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

public class UdpReceiver
{
    public static void ReceiveMessages(int port)
    {
        UdpClient udpListener = new UdpClient(port);
        Console.WriteLine($"Listening for UDP messages on port {port}...");

        try
        {
            while (true)
            {
                IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
                byte[] receivedBytes = udpListener.Receive(ref remoteEndPoint);
                string message = Encoding.UTF8.GetString(receivedBytes);

                Console.WriteLine($"Received message: '{message}' from {remoteEndPoint}");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error receiving message: {ex.Message}");
        }
        finally
        {
            udpListener.Close();
        }
    }

    public static void Main(string[] args)
    {
        // Example usage:
        // ReceiveMessages(11000);
    }
}
            

Related Topics

• TCP Socket
• Sockets Overview
• IPAddress Class