try-from man page
try-from — test program for the tcp_wrapper
The try-from command can be called via a remote shell command to find out if the hostname and address are properly recognized by the tcp_wrapper library, if username lookup works, and (SysV only) if the TLI on top of IP heuristics work. Diagnostics are reported through syslog(3) and redirected to stderr.
rsh host /some/where/try-from
hosts_access(5), hosts_options(5), tcpd(8)
Wietse Venema, Eindhoven University of Technology, The Netherlands.