c# - 需要一个更优雅的模式来关闭 TcpListener

Question

我有一个 TcpListener，它在关闭时会导致所有进行中的客户端在尝试调用 EndAcceptTcpClient 时抛出以下异常。是否可以使用更优雅的模式来允许所有现有客户端连接在 TcpListener 完全关闭之前完成？

System.ObjectDisposedException: Cannot access a disposed object. Object name: 'System.Net.Sockets.Socket'. at System.Net.Sockets.Socket.EndAccept(IAsyncResult asyncResult) at System.Net.Sockets.TcpListener.EndAcceptTcpClient(IAsyncResult asyncResult)

这是监听器设置的示例:

private TcpListener _requestListener;

---

requestListener = new TcpListener(endPoint);

requestListener.Start(1000);

requestListener.BeginAcceptTcpClient(ServiceRequestInstanceHandler, null);

当我试图关闭监听器时，我调用以下命令。这就是导致上述异常的原因。

if (_requestListener != null)
{
    _requestListener.Stop();
}

这是处理回调的代码示例，回调最终通过调用监听器 Stop() 方法来实现

private void ServiceRequestInstanceHandler(IAsyncResult result)
{
    try
    {
        using (TcpClient client = _requestListener.EndAcceptTcpClient(result))
        {
            ProcessRequest(client);
            client.Close();
        }

        //Prepare to accept the next message
        _requestListener.BeginAcceptTcpClient(ServiceRequestInstanceHandler, null);
    }
    catch (Exception ex)
    {
        if (_logger.IsErrorEnabled)
            _logger.Error("An error occured while processing a service request. ", ex);
    }
}

Answer 1

我相信要避免错误，您需要将 requestListener 对象传递给 BeginAcceptTcpClient，如下所示:

requestListener.BeginAcceptTcpClient(ServiceRequestInstanceHandler, requestListener);

供引用:http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener.beginaccepttcpclient.aspx

我个人也会重写您的方法，让您的服务器在像这样处理其他客户端之前接受一个新客户端:

private void ServiceRequestInstanceHandler(IAsyncResult result)
{
try
    {
        // You should probably check for a null result here, just in case
        if(result == null)
        {
            throw new Exception("Result is null, cannot continue");
        }
        using (TcpClient client = _requestListener.EndAcceptTcpClient(result))
        {
            // Remember this line returns immediately/does not block
            _requestListener.BeginAcceptTcpClient(ServiceRequestInstanceHandler, _requestListener);
            ProcessRequest(client);
            client.Close();
        }
    }
    catch (Exception ex)
    {
        if (_logger.IsErrorEnabled)
            _logger.Error("An error occured while processing a service request. ", ex);
    }
}

IIRC，异步内容在单独的线程上运行。

注意:上面的代码我没有测试过，但应该可以解决你的问题:)

HTH