I just had a call from a customer who said their IIS service is no longer accepting HTTP connections. They though this might be related to network settings.
Upon logging in to the system, I looked at various services that might be listening on port 80 using:
netstat -aon | findstr 80
You will get something similar to the following:
TCP 0.0.0.0:80 0.0.0.0:0 LISTENING 4
This is the system process with id 4 listening on port 80. This is normally IIS.
Once I was certain IIS was actually working, I decided to go and have a look at the IIS log files. On Windows 2003 you will find these under C:WINDOWSsystem32LogFiles
Looking in the HTTPErr folder, I found the following logged items:
#Fields: date time c-ip c-port s-ip s-port cs-version cs-method cs-uri sc-status s-siteid s-reason s-queuename
2014-07-12 22:35:05 - - - - - - - - - 6_Connections_Refused -
2014-07-12 22:35:10 - - - - - - - - - 1_Connections_Refused -
2014-07-12 22:35:25 - - - - - - - - - 1_Connections_Refused -
2014-07-12 22:35:40 - - - - - - - - - 1_Connections_Refused -
2014-07-12 22:36:10 - - - - - - - - - 1_Connections_Refused -
A list of IIS errors can be found here. Within this page, you will find the error for connection refused.
The kernel NonPagedPool memory has dropped below 20MB and http.sys has stopped receiving new connections
Now we are getting somewhere.
This is caused by the system running out of available NPP memory. A good article can be found here.
I recommend turning on aggressive memory in order to fix this issue. The article for this can be found here.