In linux, normally, it is impossible to "bind()" to the same TCP port twice. If you try to bind to the same port from second proces unix processes you'll see:
socket.error: [Errno 98] Address already in use
Install tcpkill
yum -y install dsniff --enablerepo=epel
View connections
netstat -tnpa | grep ESTABLISHED.*sshd.
Block with ip tables
iptables -A INPUT -s IP-ADDRESS -j DROP
Kill connection