stop (pause) inactive minecraft server process

minecraft-sleep.sh

#!/bin/bash
##I actually use this as part of my run.sh script, so I call minecraft first, but I've commented that out
##I run this in crontab -e as @reboot /home/minecraft/minecraft/run.sh > /dev/null 2>&1
#BINDIR=$(dirname "$(readlink -fn "$0")")
#cd "$BINDIR"
#/usr/bin/screen -d -m -S mcs /usr/bin/java -Xms512M -Xmx1536M -jar server.jar n$
#wait a minute before we start watchdogging the server
#sleep 60

# set this to the port your minecraft server is on
PORT=25565

# how frequently do we check for connections (seconds)
CHECK_DELAY=60

# script will start the server briefly duing each cycle
POLL_CYCLE=600

# how long to resume server during poll cycle
POLL_RUN=1

# delay in checking for connections during poll
POLL_DELAY=5

# If you have multiple java environments this will need to be changed
function find_pid(){
  echo $(pidof java)
}

function pause(){
 # this stops the process (like ctrl-z)
 PID=$(find_pid)
 kill -STOP $PID
}

function resume(){
 PID=$(find_pid)
 #if the PID doesn't exist, we will exit so that we don't wait for a connected user forever
 kill -CONT $PID || exit 1
}

while true; do
 # wait a bit before looping again
 sleep 60

 echo "checking for activity on $PORT"
# while ( netstat -tn | grep $PORT | grep ESTABLISHED ); do
 while ( netstat -tn | grep $PORT ); do
    #echo "still active..."
    sleep $CHECK_DELAY
 done
 
 echo "no active connections on $PORT, so pausing process $(find_pid)"
 pause

 echo "waiting for activity on $PORT, will run server for $POLL_RUN seconds every $POLL_CYCLE seconds."   
 ACTIVE=""
 while [ -z "$ACTIVE" ]; do
   echo "Resume process $(find_pid) for $POLL_RUN seconds to prevent crashes/timeouts"
   resume
   sleep $POLL_RUN
   pause
   
   echo "waiting for activity on $PORT"   
   POLL_UNTIL=$((SECONDS+POLL_CYCLE))
   while [ $SECONDS -lt $POLL_UNTIL ]; do 
     ACTIVE=`netstat -tn | grep $PORT`
     #echo "ACTIVE=$ACTIVE"
     if [ -n "$ACTIVE" ]; then 
        break
     else
        sleep $POLL_DELAY
     fi
   done
 done;

 echo "Resuming process $(find_pid) due to activty $ACTIVE"
 resume
 
 
done