There are two Houdini-specific proxy environment variables you can use to specify whether Houdini should use a proxy or not.

You can specify the variables in the user houdini.env file or create system-wide environment variables.

HOUDINI_HTTP_NOPROXY

If you have a system proxy but you don't want Houdini to use the proxy to the remote license server, you can set this variable.
Houdini 20.0 and older will not use the system NO_PROXY environment variable.

An example for HOUDNI_HTTP_NOPROXY:

HOUDINI_HTTP_NOPROXY=localhost,127.0.0.1,.domain.com

Where .domain.com will be your company domain of the license server. This can be a domain or IP address of the license server itself.

This variable controls the list of connection URL that should not go through a proxy if a proxy is setup. The default is localhost,127.0.0.1.

See libcurl CURLOPT_NOPROXY for more details.

HOUDINI_HTTP_PROXY

This variable control the proxy URL that should be used when making HTTP(s) requests. Note this variable should be used when Houdini products should be using a different proxy from the rest of the system. This variable is used in favour of the system environment variable HTTP_PROXY and HTTPS_PROXY.

See libcurl CURLOPT_PROXY for more details.