[joy]

Correct configuration can help you handle more concurrent users more effeciently,
following instructions might be helpful to you:

a) edit the following parameter according to concurrent users.

open your "fcserver.sh" file
find:
$JRE_HOME/bin/java -classpath $jre_lib:$ fcserver_lib com.topcmm.jchat.FCServer &
replace with:
$JRE_HOME/bin/java -Xms64m -Xmx512m -classpath $jre_lib:$ fcserver_lib com.topcmm.jchat.FCServer &

in fact, the added part is:
-Xms64m -Xmx512m between "java" and "-classpath".

b) open <123flashchat server installed dir>/server/etc/fcserver.xml,
set to: <message-handle-workers>500</message-handle-workers>