UdpClient Class

Namespace: System.Net.Sockets

Provides a User Datagram Protocol (UDP) client that can send and receive datagrams.

Syntax

public class UdpClient
    : IDisposable
            

Remarks

The UdpClient class provides a simple interface for sending and receiving UDP packets. It handles the underlying socket creation and management for you, simplifying UDP communication. This class is useful for scenarios where you need to broadcast messages, implement protocols that do not require reliable ordered delivery (like DNS or NTP), or create applications that communicate with devices over a network using UDP.

When you create a UdpClient object, it can be bound to a specific local port or to any available port. You can use the Connect method to establish a default remote endpoint, or you can specify the remote endpoint when sending data using the Send method. Similarly, you can receive data using Receive, which will return data from any endpoint, or use ReceiveAsync for asynchronous operations.

Constructors

UdpClient()

public UdpClient()

Initializes a new instance of the UdpClient class. This constructor binds the client to a random local port.

UdpClient(int port)

public UdpClient(int port)

Initializes a new instance of the UdpClient class and binds it to the specified local port. If the specified port is 0, the UdpClient will be bound to a random port.

UdpClient(int port, IPAddress localAddress)

public UdpClient(int port, IPAddress localAddress)

Initializes a new instance of the UdpClient class and binds it to the specified local port and IP address. If the specified port is 0, the UdpClient will be bound to a random port.

Methods

Send(byte[] datagram, int bytes, IPEndPoint endPoint)

public int Send(byte[] datagram, int bytes, IPEndPoint endPoint)

Sends UDP data to a remote device. The data is sent from the local client to the specified remote device.

Receive(ref IPEndPoint remoteEP)

public byte[] Receive(ref IPEndPoint remoteEP)

Receives UDP data from a remote device. This method blocks until a datagram is received.

Close()

public void Close()

Closes the UdpClient connection.

Examples

The following example demonstrates sending a UDP message and then receiving a response:

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

public class UdpExample
{
    public static void Main(string[] args)
    {
        // Define remote endpoint
        IPAddress ipAddress = IPAddress.Parse("127.0.0.1"); // Replace with actual IP if needed
        int remotePort = 11000;
        IPEndPoint remoteEndPoint = new IPEndPoint(ipAddress, remotePort);

        // Create a UdpClient
        using (UdpClient client = new UdpClient())
        {
            // Send a message
            string message = "Hello, UDP!";
            byte[] sendBytes = Encoding.ASCII.GetBytes(message);
            client.Send(sendBytes, sendBytes.Length, remoteEndPoint);
            Console.WriteLine($"Sent: {message} to {remoteEndPoint}");

            // Receive a response (optional, depends on server logic)
            IPEndPoint receivedFromEndPoint = null;
            byte[] receivedBytes = client.Receive(ref receivedFromEndPoint);
            string receivedMessage = Encoding.ASCII.GetString(receivedBytes);
            Console.WriteLine($"Received: {receivedMessage} from {receivedFromEndPoint}");
        }
    }
}