EUREKA !!

seems that UNLOCK is the magic bullet!

FLUSH, SET REFRESH to 1, RLOCK() seem to have no effect, but just adding UNLOCK after the REPLACE command reduced loop time from 5 seconds to 1 second !

REVISED SERVER CODE

CREATE TABLE servtab (t1 c(8),t2 c(8), t3 c(8), new l)
use servtab shared
DO WHILE reccount() < 5
=sleeper(1) && sleep 1 second
GO TOP
LOCATE FOR new
IF FOUND()
REPLACE t2 WITH TIME() , new WITH .F.
unlock && <<<< improved response time at client by 80%
ENDIF
ENDDO
brow
use

PROCEDURE sleeper
PARAMETER secs
DECLARE Sleep IN Win32API INTEGER nMilliseconds
nmilliseconds = secs * 1000
=sleep(nmilliseconds)