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[ curl-Bugs-674095 ] http request hangs on win32 under certain circumstances

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Date: Fri, 24 Jan 2003 08:04:31 -0800

Bugs item #674095, was opened at 2003-01-24 08:04
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Category: libcurl
Group: hang
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Daniel Stenberg (bagder)
Summary: http request hangs on win32 under certain circumstances

Initial Comment:
OK, here is a quite peculiar problem. We use libcurl to
perform background downloads in our win32 app. The
application creates a thread in which curl
(easy-interface) is run.

Now we found on peculiar seup where a simple http get
request will hang. This is tested and reproducible
under WindowsXP

The situation and flow of events on our test laptop is
- the PC was at home and got a DHCP setup from the
cable modem provide
- the DHCP setup however is flawed as it has an
infinite lease time
- when connecting the PC in the office, Windows thinks
that we are connected and has a valid lease and does
NOT refresh the DHCP setup from the firewall box
- network connections do not work (i.e. MSN does not
- to fix this, the usual course of action is to disable
the network interface and the reenable it
- now network connections do work (i.e. MSN connects)
- the app with the pending curl request in the thread
hangs however
- a timeout of 1 hour (or shorter) was set but doesn't
get triggered

As far as I can tell, possible causes of this could be:
- timeout does not work
- timeout does not work because of our threading
- windows API is f***ed and hangs (I guess MSN has the
homeboy advantage)

I am not sure where it hangs inside curl - haven't
debugged this far yet. As far as solutions go, maybe it
would be possible to add an optional TCP "quickcheck"
on the connection before any gethostbyname/connect call
- a check that does not hang but verifies that a
condition exists which allows for the call to proceed.
In fact such a IsConnected() call would be a nice
addition to libcurl. (The win32 API IsConnected() does
for example not work well.)

Please CC any comments and ideas also to


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Received on 2003-01-24