Hi Rohit,
"1) Out of three app server,one is giving error while connecting."
1) Did you run the niping test
niping -c -O -S <sapgwXX> -H <hostname>
on the application server where the error occurs?
What was the result?
2) Did you check in the /etc/hosts on this machine? Is there any other service using the same 33XX port as the gateway service?
br, Endre.