The current version of our I++ server is V1.6.

Our I++ server is based on version 1.5 of the I++ specification so this means it does not support any commands from version 1.6 and 1.7.
This also means it understands all the commands of 1.43 and 1.5.  However some of these commands will report not implemented and others will do a minimum to satisfy operation but without actually functioning as intended.
I have provided a list which may be helpful to understand the situation.  Please do not take this as precise but as a guide.
We have a development version V1.61 which partially implements a command from spec 1.6 to help a customer with compatibility.
I++ clients should call GetDMEVersion() to discover the server version and refrain from calling commands from later specs, but sadly some do not.
Finally we implement something which is not in the specification but is known as "ClientTool" this is a special tool which can have its properties set and allows the client software to manage the tool database, this means the whole tool handling section becomes redundant and is the preferred method for using the server.