vsntp README    See INSTALL for details on how to install and run vsntp.Obtaining the Newest Information    vsntp's official website is at...      SourceForge's home site: http://vsntp.sourceforge.net/      SourceForge's project page: https://sourceforge.net/projects/vsntp/      Tavern IMACAT's page: http://www.imacat.idv.tw/tech/vsntp.html    You can always download the newest version of vsntp from...      SourceForge: https://sourceforge.net/project/showfiles.php?group_id=99098      Tavern IMACAT's FTP: ftp://ftp.imacat.idv.tw/pub/vsntp/    imacat's PGP public key is at...      SourceForge: http://vsntp.sourceforge.net/pgpkey.asc      Tavern IMACAT's: http://www.imacat.idv.tw/me/pgpkey.ascIntroduction:    vsntp is an SNTP client daemon for machines without a sane systemtime.  The word "vsntp" stands for "SNTP for Virtual PC".  It wasoriginally designed for my GNU/Linux server running on ConnectixVirtual PC.  It runs according to RFC 1769 SNTP, connecting the NTPserver on UDP port 123.    Without Virtual PC Additions, the system time on Virtual PC iscompletely insane.  It's RTC (Real Time Clock, or CMOS time, orhardware clock) is software emulated, which does not seems to berunning.  The GNU/Linux kernel hardly maintains a system time itself.With smooth run it goes 4 seconds ahead per minute, which is nearly1.5 hours per day.  That is insane.  You can even tell it with youreyes.    David L. Mills' ntp does not work here.  It uses a method thatlearns the clock frequency drift first, and adjust the kerenl clockwith adjtimex() so that time adjustment goes smoothly, from the pointof view of system and applications.  This assumes an existing fix-speed system clock.  But this is not the case of Virtual PC.  Thesystem clock on Virtual PC is software emulated.  It can be fasteror slower now and then, depending on the load of the hosting machine.There is no fixed clock speed.  The frequency drift does not exist,then.  It dooms to fail to measure it.    There is an sntp client that comes with David L. Mills' ntppackage.  It is suggested to be run from crontab.  But crontab runsby minutes, and Virtual PC goes 4 seconds ahead per minute.  Rollingback 4 seconds every minute is insane for most applications.  It alsoincreases system load heavily to run one instance per minute.    vsntp is a workaround on this.  It runs as a daemon to eliminatesthe additional system load on every synchronization. It usessettimeofday() to synchronize the time.  It synchronizes the timewith an arbitrary interval, so that time can be accurate within asecond.    There are some defects.  Synchronizing the time too oftenintroduces heavy network load.  It introduces heavy load on thetarget NTP server, too.  You should have a working NTP server nearbythat is owned by you.  Also, since settimeofday() is called so often,high-accurate time operations like timer, etc., may not runcorrectly.    vsntp uses sleep() as the synchronization scheduler.  Reports showthat on some systems sleep() may not function normally.  If you findvsntp stops synchronization after running for some time, that thesleep() is not functioning normally on your system, you may want toswitch to the alarm() scheduler with the "-a" switch.    If you ever encounter any problem, you may check your syslog.vsntp logs detailed debugging information to syslog in log levelLOG_DEBUG with facility LOG_DAEMON.  You may turn it on in your/etc/syslog.conf with the following line:      daemon.debug  /var/log/debugand check the /var/log/debug file for the debugging message.  Rememberto remove this afterwards, for the amount of the debugging messagesmay be huge and may use up your harddisk in a very short time.  To theleast it may slow down your system for frequent harddisk I/O.    vsntp was originally written for GNU/Linux.  It uses POSIXcompatible system calls.  It should work on any POSIX compatiblesystem.  But I have yet only tested it on Cygwin.  Cygwin is known towork.  I don't have others to test and run on.  Please let me know(and submit the patch if needed) if you can port it to other systems.I know it does not work on MSWin32, for the way it handles the PIDfile path.    Please tell me if you have successfully running vsntp on othervirtual machines, like VMWare.    Generally, please tell me if you are using vsntp.  I would liketo know that I am really doing some good for the world, *^_^*  but nothaving fun myself. :p    This is my first daemon, my first socket program and my firstpublic-released C program.  Any comment or suggestion is welcome. ^_*'