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Subject: Re: CIPE Virtual NIC
From: Damion Wilson <dwilson,AT,ibl,DOT,bm>
Date: Thu, 10 May 2001 18:56:39 +0200
In-reply-to: <3BC5217C8E6D9E498F4F682CD7FF75461073BF@mail10.main.ntu.edu.sg>

Hi, Prakash

You don't have to use Overlapped I/O. In fact, you should probably start
out with synchronous I/O for experimenting. Debugging
my overlapped i/o code wasn't trivial.

I use a different Overlapped structure each for reads and writes. This only
allows me to have one simultaneous read and write request pending at a
If you try to queue any more i/o requests using the same Overlapped
before the previous one completes, you will get the error.


On Wednesday, May 09, 2001 at 23:16:41 [ADT] #PRAKASH SANDEEP# wrote:
> Hi,
> Hope this helps to sort out the problem I metioned earlier.
> I can only read from the tap device the first time it is installed. After
> that any more attempts to read from it are met by "Overlapped I/O in
> progress" error. This happens even if I ping the gateway I have set for
> my
> laptop (see the email below for reference).
> Thanks and regards,
> Sandeep
> ******************
> Hi,
> I would really appreciate any help on the problem I have.
> I have a win2k laptop witthout a physical network adapter. I am using the
> CIPE virtual adapter to obtain the ethrnet frames generated as a reult of
> TCP/IP communication. I will be transferring these frames via Bluetooth.
> I have a few problems with the CipeTapIO program. I have modified it a
> bit.
> I can get a valid handle for the virtual NIC. However, when I try to
> perform
> a ReadFile operation on the NIC I get "Overlapped I/O in progress" Error.
> This means that no data has been received on this adapter. However, this
> is
> the only adapter I have set up on my laptop and I have given it a fixed
> IP.
> I have also fixed the gateway. 
> Now, when I try to ping the gateway ARP frames should be generated (ARP
> table is empty and this is the first IP communication on starting up the
> laptop) by the TCP/IP stack right? I should be able to read these on
> ReadFile right? I wait for an event on the m_Overlapped structure used in
> ReadFile. I still do not get any packets.
> When I tried my code the first time it did give me some packets. But, now
> it
> does not. I have the problem mentioned above.
> As I said earlier I get a valid handle for the device and pass it to the
> ReadFile for overlapped I/O.
> Also, sometimes I am unable to get a valid handle for the driver. I can
> get
> a valid handle again once I restart the laptop.
> Any help on this would be really appreciated.
> Regards,
> Sandeep
> **************

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