TSRef - TypoScript Reference
4.1.8. hostname
Syntax:
[hostname = hostname1, hostname2, ...]
Comparison:
The values are compared with the fully qualiteid hostname of getenv("REMOTE_ADDR") retrieved by PHP.
Value is comma-list of domain names to match with. *-wildcard allowed but cannot be part of a string, so it must match the full host name (eg. myhost.*.com => correct, myhost.*domain.com => wrong)