JAVA高级面试进阶训练营视频教程

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　　网络编程分为阻塞和非阻塞两种方式，如果选择了阻塞方式进行编程，控制不好很容易导致程序死掉。

　　下面这段代码中：

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

        /// <summary>
        /// 接收线程
        /// </summary>
        private void receive()
        {
            while (true)
            {
                Thread.Sleep(TimeSpan.FromSeconds(1));
                this.AddTextToCommStateList(DateTime.Now.ToString() + "\t等待连接...");

                tcpClient = tcpListener.AcceptTcpClient();

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

                networkStream = tcpClient.GetStream();

                // 设置读取超时时间为10秒
                networkStream.ReadTimeout = 10000;

                // 设置写入超时时间为10秒
                networkStream.WriteTimeout = 10000;

                byte[] recvBuff = new byte[8192];
                int readBytes = 0;
                while (tcpClient != null)
                {
                    try
                    {
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t开始读取");
                        readBytes = networkStream.Read(recvBuff, 0, recvBuff.Length);
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t读取完毕");
                    }
                    catch (IOException ex)
                    {
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t接收错误");
                        this.AddTextToCommStateList(DateTime.Now.ToString() + "\t错误信息：" + ex.Message);
                        break;
                    }
        ...

　　如果去掉networkStream.ReadTimeout = 10000;和networkStream.WriteTimeout = 10000;两行，程序就有可能在

　　readBytes = networkStream.Read(recvBuff, 0, recvBuff.Length);处死掉（笔者在调试到此时将网线拔掉，发现程序就会死在这里，即使网络恢复了程序也不会恢复）。

　　查看MSDN中关于NetworkStream类的帮助信息，发现ReadTimeout和WriteTimeout属性的默认值都是Infinite（无限），即永不超时，所以networkStream.Read在读不到数时就永远不会返回。