来自 gSOAP 服务器的异步回调/事件的最佳方法是什么？
我正在设计一个用于 Windows CE 设备和 PC 之间的 Web 服务接口。 Windows CE 设备是服务器，PC 是客户端。
我决定使用 gSOAP 库来实现服务器，并使用 .NET/C# 作为客户端。我遵循了此处 一切正常。
我的问题是关于如何最好地实现从服务器到客户端的异步回调/事件。我可以想到两种方法：
- 连续轮询服务器以获取活动事件
- 一种阻塞方法，使连接保持打开状态，直到事件发生
我当前选择了选项 2，它似乎运行良好。我在客户端中使用异步方法，因此当该方法完成时（即 Windows CE 设备上发生事件时）会收到回调。然后，我立即再次调用相同的方法，以便为下一个事件做好准备。
服务器方法示例（无错误处理）：
int ns__WaitForEvent(struct soap* soap, int *eventId)
{
WaitForSingleObject(hMyServerEvent, INFINITE);
*eventId = GetCurrentEventId();
return SOAP_OK;
}
客户端示例（无错误处理）：
private void SubscribeToServerEvents()
{
var server = new MyMethods.ServicePortTypeClient(
new BasicHttpBinding(),
new EndpointAddress(myIpAddress));
AsyncCallback cb = this.Callback;
server.BeginWaitForEvent(cb, server);
}
private void Callback(IAsyncResult ar)
{
var server = (MyMethods.ServicePortType)ar.AsyncState;
var result = server.EndWaitForEvent(ar);
// Do stuff with result
}
服务器必须是多线程才能使此方法工作，并且应限制客户端的数量，以便服务器不会有大量线程挂起与阻塞方法。就我而言，这些问题都不是问题 - 使用 gSOAP 设置多线程服务器很简单，并且每台服务器只会连接一个客户端（我控制）。
这种方法有什么明显的缺点吗？您能提出更好的解决方案吗？
I am designing a webservice interface for use between a Windows CE device and a PC. The Windows CE device is server and the PC is client.
I have decided to use the gSOAP library to implement the server and I am using .NET/C# for the client. I have followed the approach described here and everything is working well.
My question is about how to best implement an asynchronous callback/event from the server to the client. I can think of two methods:
- Continuously polling the server for active events
- A blocking method that keeps the connection open until an event occurs
I have currently chosen option 2 and it seems to be working well. I use an asynchronous method in the client and therefore get a callback when the method completes, i.e. when an event occurs on the Windows CE device. I then immediately call the same method again so it is ready for the next event.
Example server method (no error handling):
int ns__WaitForEvent(struct soap* soap, int *eventId)
{
WaitForSingleObject(hMyServerEvent, INFINITE);
*eventId = GetCurrentEventId();
return SOAP_OK;
}
Example client (no error handling):
private void SubscribeToServerEvents()
{
var server = new MyMethods.ServicePortTypeClient(
new BasicHttpBinding(),
new EndpointAddress(myIpAddress));
AsyncCallback cb = this.Callback;
server.BeginWaitForEvent(cb, server);
}
private void Callback(IAsyncResult ar)
{
var server = (MyMethods.ServicePortType)ar.AsyncState;
var result = server.EndWaitForEvent(ar);
// Do stuff with result
}
The server must be multi-threaded for this approach to work, and the number of clients should be limited so the server does not have a large number of threads hanging with blocking methods. In my case none of these issues are a problem - it is simple to setup a multi-threaded server using gSOAP and there will only ever be one client (which I control) attached to each server.
Are there any significant disadvantages to this approach? Can you suggest a better solution?
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我建议将 WinCE 设备变成 Web 客户端而不是 Web 服务器，将 PC 变成服务器，客户端发生任何情况都会收到通知。这种方法更自然，您仍然可以使用 gSoap 作为肥皂客户端。在 PC 上，您应该安装一个 Web 服务器，例如 Apache 或 IIS，或者您可以创建一个 Windows 服务器来托管嵌入式轻型 Web 服务器。
I suggest to turn the WinCE device into a webclient instead of a webserver and the PC into a server, that will be notified on something happens on the client. It is more natural this approach, you can still use gSoap for a soap client. On the PC you should have a web-server like Apache or IIS installed, or you could make a Windows server that will host an embedded light webserver.