The hybrid connections feature of Azure App Service has now entered general availability and supports making calls to endpoints in nearly any network. Hybrid connections are defined against specific host and port combinations. Some example use cases include reaching databases or web services in support of your Linux app. Hybrid connections don’t require you to expose an internet-accessible endpoint or configure a VPN.
This feature is supported for apps in basic, standard, or premium App Service plans.
Read more information about hybrid connections
Learn more about App Service networking features in general