Re: [libmicrohttpd] Hanging connections

[Christian Grothoff]

I agree with Ken's points, the other thing you can do is share a
(simplified?) version of your code so we can look at it and maybe see if
there is anything wrong with it.

On 11/03/2015 04:15 PM, Kenneth Mastro wrote:
> Somebody with more knowledge may want to chime in, but I have a few random
> thoughts...
> 
> 1) If you're using 'thread per connection' and your callback just isn't
> getting called AT ALL... Is it possible that you only have 1 thread
> allotted and it's already being consumed by another request?  I.e., what
> does your call to 'MHD_start_daemon' look like?  Do you have a connection
> limit set?  What about a connection timeout?  (If you have a connection
> timeout, try reducing it to something really short - see if the symptoms
> improve.)
> 
> 2) On the browser side, use something like Firebug (for Firefox) or
> Chrome's built-in tools and see what it thinks is happening to the
> connections/requests.
> 
> 3) Try make sure all your 'GET' requests are working properly before diving
> into 'POST' (which tends to be much harder - at least it was for me).
> 
> 4) That connection callback is a little funky because it gets called twice
> for every request.  I'm assuming you're handling that, but just keep that
> in mind.
> 
> 5) Finally - I think the 0.9.45 release had something in it that fixed a
> minor bug with thread-per-connection.  I haven't tried updating to it yet
> (I'm a version or 2 behind right now), but if you're pretty sure your code
> is correct you could always try rolling back to an earlier version - see if
> a regression of some kind was introduced.  (Unlikely, but 0.9.45 hasn't
> been out very long so you never know.)
> 
> 
> As a side note - MHD is a really great library.  It can be a little
> challenging to get your 'web server' working initially, but I've found that
> it performs really well and is very reliable once you do.
> 
> 
> Ken
> 
> 
> 
> On Mon, Nov 2, 2015 at 8:18 PM, Phil Rosenberg <address@hidden>
> wrote:
> 
>> Hi
>> I have just started using microhttpd to provide web access to control
>> some software I have written. However I've just hit a problem. I'm not
>> a http expert, so please bear with me.
>>
>> I have set up MHD to respond to get and post requests. For both cases
>> I return a html form to the client with some text boxes and a submit
>> button. The form is followed by the time, so I can check that the page
>> has updated. For a post request I parse the keys to extract the
>> information I need to control my application. I'm using one thread per
>> connection. My code was initially based on the minimal example on the
>> web page, I then added the POST processing code following the
>> tutorial.
>>
>> I am using version 0.9.45 built on Windows 10 using Visual Studio 2015
>> Community Edition.
>>
>> Unfortunately about 50% of the time when I press the submit button in
>> the browser I get a loading symbol in the tab, but nothing happens.
>> Pressing the submit button again usually seems to get things working,
>> but sometimes it takes quite a few button presses.
>>
>> Running in the debugger I can see that for these hung connections my
>> first callback is not being called. I think the port is still open or
>> something, because exiting my application causes the browser to
>> immediately display a cannot connect message. It's like MHD is stuck
>> in a loop internally or something.
>>
>> I've tried connecting with IE and Edge from the local machine and from
>> Firefox from an Ubuntu machine on the same LAN. All give similar
>> symptoms.
>>
>> One possibly relevant item - I get similar hangs if I reply MHD_NO to
>> any of the callbacks, which I thought was supposed to sever the
>> connection.
>>
>> As I said I'm not an expert on HTTP, and I've only just picked up MHD,
>> so any debugging advice would be most welcome. I'm happy to do the
>> legwork, but I'm struggling to know where to start.
>>
>> Thanks in advance for any help
>>
>> Phil
>>
>>
>

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