I need to know if JBoss startup is ready, then I can do something else. But how can I detect it?
Fortunately JBoss JMX MBean can help us.

1. Use twiddle.bat to get server infomation

%JBOSS_HOME%\bin\twiddle.bat -H get
Get the values of one or more MBean attributes

usage: get [options] <name> [<attr>+]
If no attribute names are given all readable attributes are retrieved
options:
–noprefix Do not display attribute name prefixes
– Stop processing options
%JBOSS_HOME%\bin\twiddle.bat get jboss:service=invoker,type=jrmp
ServerAddress=0.0.0.0
RMIClientSocketFactoryBean=null
StateString=Started
State=3
RMIServerSocketFactoryBean=org.jboss.net.sockets.DefaultSocketFactory@ad093076
EnableClassCaching=false
SecurityDomain=null
RMIServerSocketFactory=null
Backlog=200
RMIObjectPort=4444
Name=JRMPInvoker
RMIClientSocketFactory=null

2. Example:
I write a batch script like this:

REM ***********************************
REM startup JBoss and then do something
REM ***********************************
@echo off
REM start JBoss server
start "JBoss4C server" /Min %JBOSS_HOME%binrun.bat

REM use jboss.server MBean to detect JBoss start up ready or not
REM continue to ping JBoss for max times
set jcount=0
set MAXLOOP=100
:loop
call %JBOSS_HOME%bintwiddle.bat get --noprefix "jboss.system:type=Server" Started > $flg

REM if flag is "true" means JBoss start up ready!
find /i /n /off "true" $flg

REM ERRORLEVEL=0 success,ERRORLEVEL=1 fail
if ERRORLEVEL 1 goto :FAIL_STARTUP
goto :SUCCESS_STARTUP_JBOSS

:FAIL_STARTUP
echo JBoss startup not ready!
echo wait... %jcount%
if %jcount% == %MAXLOOP% goto :EXIT
set /A jcount=%jcount%+1
goto :loop

:SUCCESS_STARTUP_JBOSS
echo JBoss start up ready!
goto :dosomething

:dosomething
REM continue your task

:EXIT
exit
@echo on

REM ***********************
REM shutdown JBoss window
REM ***********************
@echo off
:SHUTDOWN_JBOSS4C
REM shutdown JBoss server
call %JBOSS_HOME%binshutdown.bat -S

:CLOSE_WINDOW
call taskkill /f /fi "windowtitle eq JBoss4C server*" | @cls

:EXIT
exit
@echo on

Ref:
JBoss 4.0 The Official Guide