UdpClient Class

Provides a UDP (User Datagram Protocol) service.

Namespace

System.Net.Sockets

Inheritance

Object → MarshalByRefObject → UdpClient

Summary

The UdpClient class provides a simple interface for sending and receiving UDP datagrams. It allows you to send UDP packets to a specified remote host and port, and to receive incoming UDP datagrams. It handles the underlying socket creation and management, simplifying UDP communication.

Constructors

Constructor	Description
UdpClient()	Initializes a new instance of the UdpClient class.
UdpClient(int port)	Initializes a new instance of the UdpClient class and binds it to the specified local port.
UdpClient(IPEndPoint localEP)	Initializes a new instance of the UdpClient class and binds it to the specified local endpoint.
UdpClient(string hostname, int port)	Initializes a new instance of the UdpClient class and connects it to a remote host and port.

Properties

Property	Description
Active	Gets a value indicating whether the UdpClient is active.
Client	Gets or sets the underlying Socket for the UdpClient.
ExclusiveAddressUse	Gets or sets a value that specifies whether the UdpClient allows other applications to bind to the same port.
Available	Gets the number of bytes available to be read from the network buffer.

Methods

Key methods include:

• Connect(IPEndPoint remoteEP): Connects to a remote host using an IPEndPoint.
• Connect(string hostname, int port): Connects to a remote host using a hostname and port.
• Send(byte[] datagram, int bytes, IPEndPoint remoteEP): Sends UDP datagrams to a specified remote host.
• Send(byte[] datagram, int bytes): Sends UDP datagrams to the previously connected remote host.
• Receive(ref IPEndPoint remoteEP): Receives an incoming UDP datagram.
• Close(): Closes the UdpClient and releases all network resources.
• JoinMulticastGroup(IPAddress multicastAddr): Joins the specified multicast group.
• DropMulticastGroup(IPAddress multicastAddr): Leaves the specified multicast group.

Example Usage

Sending a UDP Datagram

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

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

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

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

Receiving UDP Datagrams

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

public class UdpReceiver
{
    private const int ListenPort = 11000;
    private static volatile bool stopListening = false;

    public static void StartListening()
    {
        UdpClient listener = null;
        try
        {
            listener = new UdpClient(ListenPort);
            IPEndPoint groupEP = new IPEndPoint(IPAddress.Any, ListenPort);

            Console.WriteLine($"Listening for UDP datagrams on port {ListenPort}...");

            while (!stopListening)
            {
                byte[] bytes = listener.Receive(ref groupEP);
                string message = Encoding.UTF8.GetString(bytes, 0, bytes.Length);
                Console.WriteLine($"Received '{message}' from {groupEP}");
            }
        }
        catch (SocketException se)
        {
            Console.WriteLine($"SocketException in receiver: {se.ErrorCode} {se.Message}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error in receiver: {ex.Message}");
        }
        finally
        {
            listener?.Close();
            Console.WriteLine("Receiver stopped.");
        }
    }

    public static void Stop()
    {
        stopListening = true;
    }

    public static void Main(string[] args)
    {
        Thread receiverThread = new Thread(StartListening);
        receiverThread.Start();

        Console.WriteLine("Press Enter to stop listening...");
        Console.ReadLine();

        Stop();
        receiverThread.Join(); // Wait for the receiver thread to finish
    }
}
        

See Also

• TcpClient
• Sockets
• IPAddress
• IPEndPoint