HTTP communication failure: IP inclusion list

The OpenLM system comprises of several modules, that communicate among themselves by HTTP/HTTPS protocol, over predefined ports.

Failure of this communication is likely to cause unpredictable symptoms of system malfunction.

For more information on OpenLM ports, please refer to this document.

This troubleshoot guide relates to one type of configuration that has caused system malfunction on one of our customers’ network.


The HTTP.sys IP inclusion list

Citing a Microsoft Technical Center document:

The HTTP.sys IP inclusion list allows administrators to limit the IP addresses to which HTTP.sys automatically binds when it starts. This provides functionality similar to the functionality provided by the DisableSocketPooling property that was available in IIS 5.0. At startup, HTTP.sys checks to determine if there are any entries in the IP inclusion list. If there are, HTTP.sys attempts to listen only on these IP addresses and only at initial startup. If the list has no entries, HTTP.sys listens on all available IP addresses.

So, if such an entry exists in the HTTP.sys configuration of the OpenLM Server machine, HTTP communication to any other OpenLM module (e.g. OpenLM Brokers, OpenLM Agents, EasyAdmin web application) or indeed to the license server machine itself will be restricted.

In order to solve this condition, please follow these steps:

1. View the IP inclusion list by typing:

netsh http show iplisten

in a CMD line prompt

2. If an entry exists in the IP inclusion list (e.g., do one of the following:

2a. Either add specific IPs and IP ranges to be included in the IP inclusion list, or

2b. Delete the said entry by typing:

netsh http delete iplisten ipaddress=


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