Windows tries to connect to other PC on LAN when selecting MP4 file(s)

[Dworkin]

Need your help with a really strange issue described here: http://www.overclock.net/t/1515736 (didn't receive any relevant help there, hence my trying here)

 

Here's the kicker though... since then I've discovered something that isn't mentioned in that thread: the issue (which I encounter on my desktop PC) doesn't occur when my laptop is on and connected to the same LAN. Clearly, my desktop tries to connect to my laptop whenever Windows Explorer interacts with an MP4 file, but I have no idea why.

Edited February 11, 2015 by Dworkin

[Tripredacus]

Well first of all, maybe determine whether the delay is truly network related or not. You can say it is contacting your other computer, but so far I find no proof of that.

Some ideas.

1. Noting the exact time, interact with a file... wait for the issue to persist and note the time again. Then head off to EventViewer and look at everything within that time. If it is 30 seconds, you'll only have 1 minute to bother with. If nothing relevant is in System or Application, you may need to dig into the advanced section.

2. For the second test, it is best that you have no other things running. I would leave antivirus, but if you can close everything else, it would be best. This would include items in the system tray. Reason being, you would want to get a ProcMon trace during a repeated file interaction. Less things running means less data to wade through. You can try just tracing Explorer.exe, but if you can't determine it by that alone, you'd need to not use any filters. A typical run would be to start capturing, then click the thing, wait for the behaviour to stop, then stop the capture.

3. You can check to see if the network is actually being utilized during this period as well. Various combinations of netstat commands may be enough, but if you wanted detailed info you'd need to capture network activity with something like Wireshark. Using of the capture process would be similar to how ProcMon was used.

[Dworkin]

I have stated that the problem systematically disappears when the PC in question is disconnected, or when the laptop is online. As far as proof goes that it's network related, I don't see what more you could want.

 

As stated in the other thread, I've already tried Event Viewer—nothing relevant there.

 

Procmon: I did what you said, and it just triggers a crap ton of explorer.exe entries, many of which are mp4 related, but I have no idea what to do with them.

 

Wireshark: Just clicking an MP4 indeed triggers a series of SMB/SMB2 packets from 192.168.0.91 (PC in question) to 192.168.0.94 (laptop) and back, and this doesn't happen with any other file format. If I do it while the laptop is offline, I immediately get a mix of TCP packet losses and ARP packets saying "Who has 192.168.0.94? Tell 192.168.0.91". This confirms what I already knew, but still doesn't tell me what the cause is.

[Tripredacus]

If so inclined, you may upload those traces somewhere for others to look at.

[submix8c]

Are you using the UPnP facility?

Google this

UPnP mp4

Further, seems that UPnP (of which I do *not* have installed) is for streaming a variety of files between a variety of devices (e.g. XBox). You might want to check on that. It *really* sounds like you have one of those PC's set up as the "server".

 

HTH

 

Addendum - be aware that I'm not absolutely sure this is related, since (as I said) I don't fiddle with UPnP whatsoever.

[Dworkin]

Sorry for the late reply; I kind of put this off for a while as I haven't had the time to deal with it.

 

Anyway, the issue was resolved after I randomly decided to install all the optional patches in Windows Update (I never bother to install those since they're optional and I like to avoid potential bloat, but lesson learned), so I'm deducing this was a Windows 7 bug which, by a very specific set of circumstances, triggered the symptom I described. Your help was certainly appreciated though.

Edited May 23, 2015 by Dworkin