From GridLAB-D Wiki
New in 4.0!
client_allowed -- Restrict internet address from which clients can connect to server
Synopsis
#set client_allowed=address
Remarks
Any address that doesn't match the incoming address is denied. If the address is partial, the leading part of the address must match.
Example
The address "127.0.0.1" matches "127.0." but does not match "128.0."