Specifications

APPENDIX B. IMPLEMENTATION DETAILS 36
B.3 Manager software
The driver software consists of 3 small programs that work together:
hs master This is the manager program on a site. At each site there is only one instance
of hs master that runs on the master computer. This program uses the services of
the GPS card and sends commands to the other computers.
hs daemon It is the program that listens to commands from the hs master and talks
directly to the clock cards. It runs on each computer from the system. It is supposed
to be registered by the inetd server.
hs client Is a helper program for hs master used to facilitate the communication
via a TCP/IP network.
The source files can be found in the hsmaster directory. hs client and hs daemon
aren’t called directly by the user, only hs master is. hs daemon is supposed to be regis-
tered with inetd or xinetd to run as a daemon. It only knows to receive a request/command
on s tdin and to output a reply on stdout. All the commands that it receives are executed on
the local clock card. The socke t listening is done by (x)inetd. See the installation section
for more details about this.
The hs master program checks if the clock card and GPS card kernel modules are loaded.
If they aren’t the program fails with a message telling why. Most errors encountered by
hs master are considered fatal, as they prevent the synchronization process from working.
The options available in the hs master menu corresp ond to the main procedures for the
synchronization and testing of the setup. The most important option is the one called
”Sync with PPS thread”. This is the most accurate option for synchronization because it
updates the clocks at each second to keep them from drifting apart.