Can not get command response in centos system

use common user to login，then excute
Command cmd = session.exec("ss -lnp|grep LISTEN|grep 80")
exit status =1 in centos system 。
but exit status =0 in centos system。
if i use root user to excute the Command in centos system ，that the exit status =0

I use Xshell ssh login .and exucte "ss" command is ok,
but use sshj execute "ss", error message is : bash: ss: command not found