According to the documentation there should be an option for VNET Integration for App Services when in the Overview of your App Service you go to > Network and than you should be able to setup a VNET for beeing able to give access to specific Ports to your Web App.
But I don't see this options anymore, how can I setup outbounding and inbounding tcp access over a specific port to my App Service?
Currently, there are limitations on Azure App Service on Linux.
Some features, such as virtual network integration, Azure Active Directory/third-party authentication, or Kudu site extensions, are not available yet. Once these features are available, we will update our documentation and blog about the changes.
If this is your case, you have to use App Service Environment, then it's already in a VNet and doesn't require the use of the VNet Integration feature to reach resources in the same VNet. Also, you can restrict the Inbound and Outbound traffic in the subnet level NSG. If you only want to allow/deny list of IP addresses that are allowed to access your app, you can use Static IP Restrictions.
Alternatively, you can change to use Azure App Service on windows with standard or above pricing tier. Then you can use the VNet Integration feature.
You need to use Standard SKU (or higher SKU). as soon as you switch to that - it should appear.
As of this writing, its not yet available for Windows Containers. If you switch (if you can) to linux containers, the option Vnet Integration should appear
