Check if the Secure Socket Tunneling Protocol is supported. This is accomplished by trying to establish the HTTPS layer which is used to carry SSTP traffic as described in: - http://msdn.microsoft.com/en-us/library/cc247364.aspx
Current SSTP server implementations: - Microsoft Windows (Server 2008/Server 2012) - MikroTik RouterOS - SEIL (http://www.seil.jp)
nmap -sV -sC <target>
443/tcp open https |_sstp-discover: SSTP is supported.