IIS and Skype

I couldn't browse to the default website running on an XP SP2 machine earlier today, which was odd, since it worked yesterday, and I hadn't done anything since but reboot. Event Viewer said that IIS couldn't bind instance 1. w3svc/1 was configured to run on port 80. I thought at first that it might be something to do with the new firewall in XP SP2 blocking IIS, but that seemed odd and besides I couldn't find any mention of IIS in the firewall UI.

Then I thought of trying Port Reporter to see what was listening on port 80, and I quickly discovered that it wasn't IIS, but Skype. I dug into the Skype UI and found that "Use port 80 as an alternative for incoming connections" was checked. Clearing this made the problem go away.

This is quite odd because I've been running Skype and IIS 5.1 on another XP machine for months without problems. I just checked and "port 80" was selected on that machine's Skype too.


  • Two things that I can think of:

    1. Load order has changed, so that now Skype beats IIS in the race to bind to port 80

    2. IIS has changed so that now it doesn't bind to, but to the actual-NIC-IP-address:80.

  • I had the same issue. Default website wouldn't start when on port 80, give "unexpected error 0x8ffe2740" which is microsofts way of saying port already in use (see their support kb). Altho netstat -a didn't list port 80 as being used, when I stopped skype, all was fine. I too had the "use 80 and 443 as alternatives" checked, so I unchecked that.

  • cmd
    netstat -a -b

    can help you find which apps are listening on which ports too

  • This post helped me a lot! xampplite's apache wasn't loading and when I saw skype was on port 80 I was thinking... bandwidth stealage or something from skype...

    But just as incoming connections! thanks!

  • Just in case anyone else comes here looking for the setting in Skype, it is:

    Tools->Options->Advanced->Connection->"Use port 80 and 443 as alternatives for incoming connections"

  • *WHY* would Skype use ports 80 and 443... HTTP and HTTPS ports; it just does not make any sense to do so.

  • To get around complicated Port Forward/Blocks/Proxy setups I guess

  • Are Skype trying to pee people off, binding to port 80 without warning?

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