[Winpcap-users] winpcap not capturing anything

[Imre Magyar]

Hello all,

I've spent a couple weeks trying to figure this out on my own, but to no avail and no amount of searching seems to help me find answers, so I'm hoping somebody out there can help.

I have a Windows .Net application that uses multiple managed Visual C++ DLLs, one of which interfaces to winpcap. The program model is fairly simple; upon entry to the DLL I open the interface with pcap_open(), spawn a separate thread to repeatedly call pcap_next_ex() while the main thread returns to managed context to continue the main application thread.

The problem is that pcap_next_ex() never manages to see a single packet. Running wireshark on the same interface simultaneously verifies that the packets are on the wire, but I never see a single one.

But it gets stranger, because everything works fine on some Windows PCs (all running XP) yet this happens reliably on others.

If I take the DLL code and change it such that it's run as a standard standalone WIN32 application, everything works perfectly, so I think that the problem isn't winpcap itself, just something having to do with the .net application contexts.

So at the risk of asking about something that is obvious to everyone else, could someone please help me with some ideas as to what's going on?

Thank-you!

--Imre M.

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