.NET Documentation

UdpClient Class

Provides UDP network services.

Remarks

The UdpClient class provides a simple client for sending and receiving datagrams using UDP. A datagram is a variable-length chunk of data. UDP is a connectionless protocol, which means that a connection is not established before sending data. This makes UDP suitable for applications that require fast, low-overhead, or real-time transmissions. However, UDP does not guarantee that datagrams will arrive in the order they were sent, or that they will arrive at all.

The UdpClient class handles the details of UDP socket programming, allowing you to focus on the application logic. It provides methods for sending and receiving datagrams, specifying remote and local endpoints, and managing socket options.

Constructors

• UdpClient(): Initializes a new instance of the UdpClient class.
• UdpClient(Int32): Initializes a new instance of the UdpClient class and binds it to the specified local port.
• UdpClient(IPEndPoint): Initializes a new instance of the UdpClient class and binds it to the specified local endpoint.
• UdpClient(string, Int32): Initializes a new instance of the UdpClient class and binds it to the specified port on the specified host.

Properties

• Client: Gets or sets the underlying Socket.
• ExclusiveAddressUse: Gets or sets a value that indicates whether the UdpClient should attempt to bind exclusively to the specified port.
• Client.IsBound: Gets a value indicating whether the Socket is bound.

Methods

• Connect(IPEndPoint): Connects the UDP client to a remote host.
• Connect(string, int): Connects the UDP client to a remote host.
• ReceiveAsync(): Asynchronously receives a datagram from the network.
• SendAsync(byte[], int, IPEndPoint): Asynchronously sends data to a remote host.
• Close(): Releases all resources used by the UdpClient.
• Dispose(): Releases all resources used by the UdpClient.

Example

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

public class UdpExample
{
    public static async Task Run()
    {
        // --- Receiver ---
        var receiver = new UdpClient(11000); // Listen on port 11000
        Console.WriteLine("UDP Receiver started on port 11000.");

        Task.Run(async () =>
        {
            while (true)
            {
                UdpReceiveResult result = await receiver.ReceiveAsync();
                string message = Encoding.ASCII.GetString(result.Buffer);
                Console.WriteLine($"Received from {result.RemoteEndPoint}: {message}");
            }
        });

        // --- Sender ---
        var sender = new UdpClient();
        IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Loopback, 11000); // Send to localhost on port 11000

        Console.WriteLine("Enter messages to send (type 'exit' to quit):");
        string input;
        while ((input = Console.ReadLine()) != "exit")
        {
            byte[] data = Encoding.ASCII.GetBytes(input);
            await sender.SendAsync(data, data.Length, remoteEndPoint);
            Console.WriteLine($"Sent: {input}");
        }

        sender.Close();
        receiver.Close();
        Console.WriteLine("Sender and Receiver closed.");
    }
}