The Build Application XML Keys feature a key called HardLink. This key is documented to represent the "signature" for merged client-server applications. The intent of this key is to link the client and server software together such that, if the HardLink does not match, the client cannot connect to the server.

Prior to 4D v11 SQL Release 5 (11.5) the HardLink was not enforced. Any client could attempt to connect to the server regardless of the HardLink value. Starting with 4D 11.5 this is no longer the case. The HardLink of the client must match that of the server, else the connection is refused.

A blank value for HardLink disables the feature.

IMPORTANT: if the HardLink feature is enabled for a deployment that did not previously use it, all of the client installations must be manually updated. In other words the Automatic Client Update feature cannot be used to update the clients because the existing clients do not have the update HardLink value; they will not be able to connect to the server.

HardLink is a security feature. Bypassing it in some way would defeat its purpose.