将SocketAsyncEventArgs与ReceiveAsync重用会导致无限循环

Question

我正在编写一个只使用一个套接字的简单套接字客户端.所以我想我可以为所有接收操作重用一个SocketAsyncEventArgs.只要连接插座,它就能正常工作.当服务器断开连接时,客户端将在控制台中输入无限接收循环垃圾邮件"接收成功".

当套接字断开连接时,e.SocketError!= SocketError.Success是不是真的？

以下是代码的一部分:

private void Completed(object sender, SocketAsyncEventArgs e)
{
   if (e.SocketError != SocketError.Success)
      status = 0;

   System.Console.WriteLine(e.LastOperation + " " + e.SocketError);

   if (status == 1)
   {
      switch (e.LastOperation)
      {
         case SocketAsyncOperation.Connect:
            ProcessConnect(e);
            break;
         case SocketAsyncOperation.Receive:
            ProcessReceive(e);
            break;
         case SocketAsyncOperation.Send:
            ProcessSend(e);
            break;
         default:
            status = 0;
            break;
      }
   }

   if (status != 1)
      CloseSocket();
}

private void ProcessReceive(SocketAsyncEventArgs e)
{
   if (!socket.ReceiveAsync(e))
      Completed(null, e);
}

Answer 1

如果您的套接字设置为字节流,那么您可能会得到一个零字节的回调,这表明已经发生了正常的套接字关闭,并且不会再读取任何字节.只需在代码中检查一下,例如

private void ProcessReceive( SocketAsyncEventArgs e )
{
    AsyncUserToken token = e.UserToken as AsyncUserToken;
    if( e.ByteTransferred > 0 && e.SocketError == SocketError.Success )
    {
        // .. process normally ..
    }
    else
    {
        CloseClientSocket( e );
    }
}

private void CloseClientSocket( SocketAsyncEventArgs e )
{
    AsyncUserToken token = e.UserToken as AsyncUserToken;
    try
    {
        token.Socket.Shutdown( SocketShutdown.Send );
    }
    // throws error if it's already closed
    catch( Exception ) {}
    token.Socket.Close();
}

当然,你还需要阻止你的客户尝试使用套接字,但我相信你可以解决这个问题.