March 26, 2020
Minimum TLS version with Azure App Services
Older .NET Framework versions defaulted to use a TLS version of 1.0 or 1.1. Today, TLS 1.2 is the newest. As of 2018, Azure App Services default to TLS 1.2. This means that you might run into issues with older .NET applications failed to issue web requests against apps/apis hosted on these app services.
“The underlying connection was closed: An unexpected error occurred on a send.
This problem especially presents itself for .NET framework applications versions 4.6.1 and lower. These older applications don’t default to TLS 1.2 when issuing web requests.
There are two ways to fix it. One is to force the .NET client code to default to TLS 1.2 (as long as the framework version supports it).
Another way is to choose the minimum TLS version on an Azure App Service . As mentioned earlier, Azure App Services default to Tls 1.2 in 2018.
You can do this from the TLS/SSL settings blade in an Azure App Service.