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

namespace ConsoleApplication4
{
    internal class UdpState
    {
        public UdpClient UdpClient { get; set;}
        public IPEndPoint RemoteEndPoint { get; set; }
        
        public UdpState(UdpClient client)
        {
            this.UdpClient = client;
        }
    }
    
    class Program
    {
        private static bool _isRunning = true;
        
        static void Main(string[] args)
        {
            Console.CancelKeyPress += (sender, e) => 
            {
                _isRunning = false;
                e.Cancel = true;
            };
            
            try
            {
                var udpClient = new UdpClient(3340);
                udpClient.Client.ReceiveBufferSize = 3 * 1024 * 1024;
                
                // 开始接收
                udpClient.BeginReceive(ReceiveCallback, new UdpState(udpClient));
                
                Console.WriteLine("UDP服务器已启动，按Ctrl+C停止...");
                
                // 保持程序运行
                while (_isRunning)
                {
                    Thread.Sleep(100);
                }
                
                udpClient.Close();
                Console.WriteLine("服务器已停止");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"启动失败: {ex.Message}");
            }
        }

        public static void ReceiveCallback(IAsyncResult ar)
        {
            UdpState state = ar.AsyncState as UdpState;
            
            try
            {
                // 1. 先获取接收到的数据
                IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
                byte[] receivedData = state.UdpClient.EndReceive(ar, ref remoteEndPoint);
                
                // 2. 立即开始下一次接收（不等待数据处理完成）
                state.UdpClient.BeginReceive(ReceiveCallback, state);
                
                // 3. 异步处理数据，避免阻塞接收
                ThreadPool.QueueUserWorkItem(_ => 
                {
                    ProcessData(receivedData, remoteEndPoint, state.UdpClient);
                });
            }
            catch (ObjectDisposedException)
            {
                // 正常关闭，忽略
            }
            catch (SocketException ex)
            {
                //Console.WriteLine($"网络错误: {ex.SocketErrorCode} - {ex.Message}");
                
                //// 尝试重新开始接收
                //if (_isRunning && state?.UdpClient?.Client != null)
                //{
                //    try
                //    {
                //        state.UdpClient.BeginReceive(ReceiveCallback, state);
                //    }
                //    catch { }
                //}
            }
            catch (Exception ex)
            {
                //Console.WriteLine($"接收回调错误: {ex.Message}");
            }
        }
        
        private static void ProcessData(byte[] data, IPEndPoint remoteEP, UdpClient udpClient)
        {
            try
            {
                //// 这里是您的数据处理逻辑
                //Console.WriteLine($"收到来自 {remoteEP} 的数据，长度: {data.Length} 字节");
                
                //// 示例：解码为字符串
                //if (data.Length > 0)
                //{
                //    string text = Encoding.UTF8.GetString(data);
                //    Console.WriteLine($"内容: {text}");
                //}
                
                //// 这里可以处理复杂的业务逻辑
                //// 例如：数据库操作、文件处理、复杂计算等
                
                //// 如果需要回复
                //if (data.Length > 0)
                //{
                //    byte[] response = Encoding.UTF8.GetBytes($"已收到: {data.Length} 字节");
                //    udpClient.Send(response, response.Length, remoteEP);
                //}
            }
            catch (Exception ex)
            {
                //Console.WriteLine($"数据处理失败: {ex.Message}");
            }
        }
    }
}