解決C#網絡通信編程的阻塞問題

　　網絡編程分為阻塞和非阻塞兩種方式，如果選擇了阻塞方式進行編程，控制不好很容易導致程序死掉。

　　下面這段代碼中：

        ...     
        TcpListener tcpListener = null;
        TcpClient tcpClient = null;
        NetworkStream networkStream = null;
        ...

        /// <summary>
        /// 接收線程
        /// </summary>
        private void receive()
        {
            while (true)
            {
                Thread.Sleep(TimeSpan.FromSeconds(1));
                this.AddTextToCommStateList(DateTime.Now.ToString() + "\t等待連接...");

                tcpClient = tcpListener.AcceptTcpClient();

                Thread.Sleep(TimeSpan.FromSeconds(1));
                this.AddTextToCommStateList(DateTime.Now.ToString() + "\t已連接");

                networkStream = tcpClient.GetStream();

                // 設置讀取超時時間為10秒
                networkStream.ReadTimeout = 10000;

                // 設置寫入超時時間為10秒
                networkStream.WriteTimeout = 10000;

                byte[] recvBuff = new byte[8192];
                int readBytes = 0;
                while (tcpClient != null)
                {
                    try
                    {
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t開始讀取");
                        readBytes = networkStream.Read(recvBuff, 0, recvBuff.Length);
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t讀取完畢");
                    }
                    catch (IOException ex)
                    {
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t接收錯誤");
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t錯誤信息：" + ex.Message);
                        break;
                    }
        ...

　　如果去掉networkStream.ReadTimeout = 10000;和networkStream.WriteTimeout = 10000;兩行，程序就有可能在

　　readBytes = networkStream.Read(recvBuff, 0, recvBuff.Length);處死掉（筆者在調試到此時將網線拔掉，發現程序就會死在這里，即使網絡恢復了程序也不會恢復）。

　　查看MSDN中關於NetworkStream類的幫助信息，發現ReadTimeout和WriteTimeout屬性的默認值都是Infinite（無限），即永不超時，所以networkStream.Read在讀不到數時就永遠不會返回。