George - connection is getting closed immediately. So customer can't do what you suggested.

Here is some background.

Customer is trying to telnet to our virtual IP hosted in F5 loadbalancer. Network team has implemented access control list and customer IPs are allowed explicitly in network devices (asa firewall/router). So any hit from customer IP comes through network devices-> F5 load balancer. Other customers were able to telnet to the same virtual IP on port 443.