MDATE: program for synchronising machines. Mdate is intended to be used as a simple device for keeping several machine clocks in sync over a small size local area network. It is based on the older programs rdate and ping. The most important change is that mdate uses ICMP timestamps. This makes it far more accurate than rdate. Over short distances (say, within a building) mdate can synchronise to within about 10 milliseconds, which should be close enough for most purposes. The disadvantage is that you have to be super-user to use mdate even just for testing. Mdate also provides several options for testing and debugging. TESTED and believed to work on SUN-OS 3.5 and HP-UX 8 & 9 . INSTALLATION Before starting to compile mdate, the installer should determine the QUANTUM, which is the smallest time interval that the local machine can measure. I have provided a supplementary program called tick to help with this. You should then edit the source file site.h to define QUANTUM correctly. This must be an integer > 0; unit = millisec; default = 1. Do: make tick tick Tick is a simple program; it should work on any Unix machine. It calls gettimeofday() repeatedly. Then it prints out the value of each call and the differences between each call & the previous. On our 712, the diffs are typically all ~~ 14 microseconds. Since this is < 1 millisec, QUANTUM should be defined as 1 (this is the default and the smallest diff that mdate can measure even in principle). On our SUNS (3/60) most of the diffs are 1 but some are ~~20000. Each large diff goes with a time value that is an exact multiple of 20000. This means that the system clock only moves every 20 msec, but each call of gettimeofday() advances the microsecond counter by 1 unit irrespective of how much time has actually passed. So the correct QUANTUM is 20. Other things you might need to edit in site.h are: OLDGETHOST Indicates that gethostbyname() returns just one address: modern versions return a pointer to a list. OLDSELECT Indicates that select() lacks the supplementary macros fd_set (etc) that construct suitable bitmasks. NORANDOM, NOADJTIME Indicate that these are lacking. Then edit Makefile to reflect the install directories, etc: then make mdate make install
