解决C#网络通信编程的阻塞问题

　　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。