1. 服务端

    internal class Program
    {
        static void Main(string[] args)
        {
            //1.创建Socket
            Socket socketServer =new Socket(AddressFamily.InterNetwork,SocketType.Dgram,ProtocolType.Udp);
            //2.绑定IP、端口号
            EndPoint endPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 5566);
            socketServer.Bind(endPoint);
            //3.接收消息
            byte[] buffer = new byte[1024];
            EndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);
            int length = socketServer.ReceiveFrom(buffer, ref remoteEP);
            Console.WriteLine(Encoding.UTF8.GetString(buffer, 0, length));
            socketServer.Close();
            Console.ReadLine();
        }
    }

2.客户端

internal class Program
{
    static void Main(string[] args)
    {
        // 创建Socket
        Socket socketClient = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,             ProtocolType.Udp);

        // 目标IP和端口号
        EndPoint endPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 5566);

        // 发送消息
        string message = "Hello, Server!";
        byte[] buffer = Encoding.UTF8.GetBytes(message);
        socketClient.SendTo(buffer, endPoint);
        Console.WriteLine("消息已发送");
        socketClient.Close();
        Console.ReadLine();
    }
}

3.执行

先启动服务端exe，再启动客户端exe，客户端会向服务端发送消息。