Handling simultaneous HTTP requests

[bgowland]

For the nDroidService I have a thread which uses the HttpListener class in synchronous mode. I create the listener instance and then use...

Code:

listener.GetContext();

...which blocks the thread until a request comes in. I then process the request and respond within the same thread and loop back to that line to listen/block again.

I want to expand the code to just simply take a request and put it out to a different thread to handle in its own time rather than process in a synchronous manner. I've looked at the BeginGetContext method of HttpListener but I can't get my head around how to use it and I'm not sure it's what I want anyway.

Anybody have any ideas for handling multiple HTTP connections/requests/responses simultaneously?

[whurlston]

Have you looked at http://msdn.microsoft.com/en-us/library/...ntext.aspx ?

[bgowland]

Have you looked at http://msdn.microsoft.com/en-us/library/...ntext.aspx ?

Yes thanks, in fact I keep coming back to that page with the numerous searches I've done today. It explains how to handle a single request/response asynchronously but I don't get how to handle multiple async requests with that API. I'm possibly just missing the point somewhere - perhaps the programmer part of my brain just isn't working today.

[whurlston]

The example is a console app so it exits after it gets a single request and responds to it. In a windows form (or service) where you are not needing to end the application and return to the command line, you would simply remove the following two lines from the main code block:

Code:

result.AsyncWaitHandle.WaitOne();
    listener.Close();

It should then respond to any requests until the listener is closed. You would close the listener when closing the form or stopping the service.

I can do a quick example for you later tonight. Do you want a service, NPVR plugin or some other example?

[whurlston]

I actually found a pretty good example: http://www.west-wind.com/weblog/posts/20...es-of-code

Edit: and another: http://www.dreamincode.net/forums/topic/...threading/

Apparently, you have to start another instance of IAsyncResult result = listener.BeginGetContext(new AsyncCallback(ListenerCallback), listener); after you finish handling one.

[bgowland]

I actually found a pretty good example: http://www.west-wind.com/weblog/posts/20...es-of-code

Thanks for taking the time to help - I just seemed to be going around in circles doing searches. That example goes a bit further to help understand it than the MSDN code snippets - I'll give it a go.

Cheers,
Brian

[Ommina]

Apparently, you have to start another instance of IAsyncResult result = listener.BeginGetContext(new AsyncCallback(ListenerCallback), listener); after you finish handling one.

The route I take:

Create the HttpListener
Add prefixes
Spin up a thread using QueueUserWorkItem, passing to the target method the listener object.

Inside the target method:

.Start() the listener
Start a loop on a class variable (_KeepRunning or whatever)
Call .BeginGetContext, giving it method DoStuff
.WaitOne on the IAsynchResult returned
Back to start of loop

Do your actual stuff in the DoStuff.

Keep in mind that both the original target method and DoStuff will be on new threads, so all the cross-thread considerations need to be, uh, considered.

So you have your original method that starts the ball rolling. It, in turn, start methods B on a new thread. Method B contains a loop that repeatedly calls BeginGetContext after .WaitOne returns. Method C does stuff.

And I really hope that I didn't just confuse things even more. . .

[bgowland]

The route I take:

Spin up a thread using QueueUserWorkItem, passing to the target method the listener object.

Interesting. I also came across this in my searches but haven't tried it yet. Thanks.

[bgowland]

Thanks both for the suggestions.

I persevered with the west-wind.com example linked by whurlston and now have it working. Had a few problems along the way and it still needs some tweaks but my code is pretty close to what I want now.

Cheers,
Brian