when running amateur radio digital modes all computers must be synced together
in order to have a qso. these are the 2 most popular apps to do the job.
http://dimension-4.en.softonic.com/ dimension 4 http://www.timesynctool.com/ timesync
http://www.maniaradio.it/en/bkttimesync.html mania timesync
if you have others please insert them here