You can set the Subject Name Indicator (SNI) name for a .NET client by using the following property: 

Progress.Open4GL.RunTimeProperties.ServerName = "servername";
servername
Specifies the server name in TLS connection initialization for client that it sends to the server as part of the TLS negotiation.

For example, Progress.Open4GL.RunTimeProperties.ServerName = "www.example.com";

If the .NET client does not send any valid SNI name available in the server configuration, the server selects a default virtual hostname and returns the respective certificate.