需要引用using System.Net.Sockets; using System.Net;兩個命名空間;

namespace TcpServer  //服務器
{
    class Program
    {
        public static List<Client> clientList = new List<Client>();
       
        static void Main(string[] args)
        {
            Socket tcpServer = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);//創建socket對象
            tcpServer.Bind(new IPEndPoint(IPAddress.Parse("192.168.1.145"), 8090));//綁定IP和申請端口

            tcpServer.Listen(100);//設置客戶端最大連接數
            Console.WriteLine("服務器已啟動，等待連接.........");
            while (true)//循環等待新客戶端的連接
            {
                Socket clientSocket = tcpServer.Accept();
                Console.WriteLine((clientSocket.RemoteEndPoint as IPEndPoint).Address+"已連接");
                Client client = new Client(clientSocket);
                clientList.Add(client);
            }
        }
        public static void BroadcastMessage(string message, Client clientSocket)//這個函數用來廣播接收到的客戶端消息  參數1為消息，參數2為消息來源（客戶端）
        {
            var onConnectedList = new List<Client>();//用來存儲已斷開服務器連接的客戶端

            foreach (var client in clientList)//遍歷已經存儲的客戶端
            {
                if (clientSocket == client)//如果該客戶端是消息來源，則不重復發送消息給該客戶端
                {
                    continue;
                }
                if (client.Connected)//判斷該客戶端的狀態
                {
                    client.SendMessage(client.ip + ":" + message);//
                }
                else//把已斷開連接的客戶端放到數組中
                {
                    onConnectedList.Add(client);
                }
            }
            foreach (var temp in onConnectedList)//廣播完之后從存儲已連接客戶端集合中移除掉已斷開連接的客戶端
            {
                clientList.Remove(temp);
            }
        }
    }
}

namespace TcpServer  
{
    class Client
    {
        private Socket clientSocket;
        private Thread t;
        public string ip = "";
        private byte[] data = new byte[1024];
        public Client(Socket socket)
        {
            clientSocket = socket;
            ip = (clientSocket.RemoteEndPoint as IPEndPoint).Address.ToString();//獲取客戶端的ip
            t = new Thread(ReceiveMessage);//開啟線程執行循環接收消息
            t.Start();
        }
        private void ReceiveMessage()//接收消息
        {
            int length = 0;//初始化消息的長度
            while (true)//循環接收消息
            {
                length = clientSocket.Receive(data);//獲取存放消息數據數組的長度
                if (clientSocket.Poll(10, SelectMode.SelectRead))//？？？？
                {
                    clientSocket.Close();
                    break;
                }
                if (length != 0)//判斷是否有數組內是否存放消息數據
                {
                    string message = Encoding.UTF8.GetString(data, 0, length);//Byte轉為string
                    Program.BroadcastMessage(message, this);//廣播給其他客戶端
                    Console.WriteLine("來自" + (clientSocket.RemoteEndPoint as IPEndPoint).Address + ":" + message);//輸出到服務器控制臺
                    length = 0;//歸0
                }
            }
        }
        public void SendMessage(string message)//發送消息
        {
            byte[] data = Encoding.UTF8.GetBytes(message);
            clientSocket.Send(data);
        }
        public bool Connected//獲取該客戶端的狀態
        {
            get { return clientSocket.Connected; }
        }
    }
}

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