dOPC XGate supports a basic user authentication mechnism.
Create a file (e.g. with Editor) and name it passwd (without extention).
Type in the following:
[USER]
username=password
anotheruser=hispassw
where the word left of the equals sign is the username and the other one the password.
Put this file...
...for normal server protection: in the dOPC XGate main folder (normally installed in the folder Kassl in your Programs folder).
...for web server protection (see also dOPC XGate as web server): in the folder you want to protect.
Remark:
In this version of dOPC XGate it is not possible to have protection for a single OPC server. The denoted users and passwords are global for all connected OPC servers.