As there is no connection between Plugin and Server, it seems not to be possible to get the Server Name. ComputerName() is a Script function which can be used to create a variable in script which then can be evaluated in Plugin as a macro variable. However, this is not 100% reliable, e.g. if the qvw file has been moved from one Server to another one without script reload.
Another "instant" method to get the Server Name is:
1.) Enable Auditing on Server. This willl create a file <logfolderonserver\Audit_<SERVER>...log
2.) Allow read access to the logfile from QVPlugin Client.
3.) If Plugin session is visible in Audit_<SERVER>...log, Server name is equal to <SERVER> part of the log file name.