Ansible: Other option available for telnet check of open ports?
You can use the Ansible wait_for module which checks a specific TCP port is open.
Since in this case, all ports should be open already, we can use a minimal no. of retries, just enough to cover network issues:
- name: Check all port numbers are accessible from the current host
  wait_for:
    host: mywebserver.com
    port: &quot;{{ item }}&quot;
    state: started         # Port should be open
    delay: 0               # No wait before first check (sec)
    timeout: 3             # Stop checking after timeout (sec)
  ignore_errors: yes
  with_items:
    - 443
    - 80
    - 80443

By default, Ansible will check once every second (configurable in Ansible 2.3 using the sleep attribute), so this will check 3 times per port.
Run this in a playbook against your inventory of 400+ hosts - Ansible will check in parallel that all hosts can reach mywebserver.com on those ports.

the parallelism is subject to the forks setting in your ansible.cfg.

We use ignore_errors: yes here so that any errors are marked in red but do not stop execution.
Open ports are reported as ok items in output and closed ports are reported as failed (you must use -vv flag on ansible-playbook to see this output).
Fine-tuning output
If you want more specific output for the success and failure cases, the code must be more complex, adding a second task:

wait_for task must register a variable
the second task produces output using debug based on success/failure condition (e.g. using Jinja2 conditional expression)
then you need to put both these tasks in an include file (without any with_items loop), and write a main playbook task that uses an include ... with_items to call the include file once per port.