Limit number of telnet connection from a client

You can specify how many telnet connections are allowed to a telnet server from a host.
This can be done using the Firewall tool "iptables" and its module "connlimit".

The configuration for doing this is:

iptables -A INPUT -p tcp --syn --dport 23 -m connlimit --connlimit-above 3 -j REJECT

The above command will allow only 3 concurrent telnet connection from a host.