UdpClient Class

The UdpClient class provides simple methods for sending and receiving UDP datagrams.

Namespace: System.Net.Sockets

Assembly: System.Net.Sockets.dll

Syntax

public class UdpClient : IDisposable
{
    // Constructors
    public UdpClient();
    public UdpClient(int port);
    public UdpClient(IPEndPoint localEP);
    public UdpClient(string hostname, int port);
    public UdpClient(AddressFamily family);
    
    // Properties
    public bool Active { get; }
    public IPEndPoint Client { get; set; }
    public bool EnableBroadcast { get; set; }
    public int Ttl { get; set; }
    public bool DontFragment { get; set; }
    public short MulticastLoopback { get; set; }
    
    // Methods
    public void Close();
    public void Connect(string hostname, int port);
    public void Connect(IPEndPoint remoteEP);
    public void Connect(IPAddress address, int port);
    public void DropMulticastGroup(IPAddress multicastAddr);
    public void DropMulticastGroup(IPAddress multicastAddr, int ifindex);
    public void JoinMulticastGroup(IPAddress multicastAddr);
    public void JoinMulticastGroup(IPAddress multicastAddr, int ifindex);
    public void Send(byte[] dgram, int bytes);
    public void Send(byte[] dgram, int bytes, string hostname, int port);
    public Task SendAsync(byte[] datagram, int bytes);
    public Task SendAsync(byte[] datagram, int bytes, IPEndPoint endPoint);
    public Task ReceiveAsync();
    public Task SendAsync(ReadOnlyMemory buffer, IPEndPoint remoteEndPoint);
    // etc.
}

Remarks

The UdpClient class encapsulates a UDP socket and provides higher‑level methods for sending and receiving data. It is designed for simple scenarios; for full control use the Socket class.

UDP is connectionless and does not guarantee delivery, ordering, or duplicate protection of packets.

Examples

Sending a Datagram

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

class Program
{
    static void Main()
    {
        using var client = new UdpClient();
        var remoteEndPoint = new IPEndPoint(IPAddress.Parse("239.0.0.222"), 11000);
        var message = Encoding.UTF8.GetBytes("Hello UDP!");
        client.Send(message, message.Length, remoteEndPoint);
        Console.WriteLine("Message sent.");
    }
}

Receiving Datagrams Asynchronously

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

class Receiver
{
    static async Task Main()
    {
        using var udp = new UdpClient(11000);
        Console.WriteLine("Listening for UDP datagrams on port 11000...");
        while (true)
        {
            var result = await udp.ReceiveAsync();
            var msg = Encoding.UTF8.GetString(result.Buffer);
            Console.WriteLine($"> Received from {result.RemoteEndPoint}: {msg}");
        }
    }
}