My ColdFusion VPS runs IIS 6.0 on Windows Server 2003.  I wanted to run Apache 2.2 on this server as well, and bind it to the IP address that IIS 6.0 wasn’t using.  I opened the IIS management console to force IIS to listen on a single IP address, but when trying to start Apache I received an “already in use” error.  I double checked that IIS was configured to listen on one IP address, and Apache was configured to listen on the other.  Then I tried several variations of service startup order, etc, still without success.

Let me explain my requirements clearly: I wanted IIS and Apache to each use port 80 of different IP addresses.  Before you leave a comment explaining I could have had them listen on different ports– I know that, but it’s not what I wanted.

My research lead me to this Microsoft knowledgebase article: http://support.microsoft.com/default.aspx?scid=kb;en-us;259349 which referenced IIS 5.0, but I assumed was relevant.  The crux of the matter is this:  “To enhance performance, IIS 5.0 uses “socket pooling”, in which IIS binds to all IP addresses when it starts.”  Yep, you read that correctly.  Regardless of the settings you made in the IIS console, it will bind to ALL available IP addresses.

The workaround in the article is as follows:

1. Change to the C:\Inetpub\AdminScripts directory.
2. Execute the following command: CSCRIPT ADSUTIL.VBS SET W3SVC/DisableSocketPooling TRUE

Apparently there are some differences between IIS 5 and 6, because this didn’t correct the problem.  Fortunately I was able to discover something that worked by browsing around a few other sites.

First, you need to install the Support Tools from the Windows Server 2003 cd.  This includes the httpcfg.exe tool, which is what you can use to force IIS to listen only on specific IP addresses.  After you have this installed (there is a start menu option that will open up a command prompt in the correct directory) here are the commands to make the fix:

1. net stop http /y (This stops IIS)
2. httpcfg.exe set iplisten /i 10.0.0.2:80 (You must specify the port! Or it will still steal them!)
3. net start w3svc (Restart IIS)
4. Start up Apache

I wasn’t able to find any documentation explaining why it didn’t work when I didn’t specify the port.  I guess IIS needs very specific rules when it comes to getting along with other HTTP servers.  I have yet to have this problem with IIS 7.0, mainly because I haven’t tried installing Apache on my Windows 2008 box.  When I try it, I’ll keep you posted as to whether this fix still works.  Or if it’s required… which I’m sure it is since it’s not a bug, it’s a performance enhancer.  I wonder if Microsoft’s STMP service uses a similar “mail enhancement” feature to grab all port 25s?