JMeter TCPSampler - how to handle a custom protocol with a periodic keep alive?

I am relatively new to JMeter however I have been doing Performance testing for almost a decade.

I am working with a proprietary TCP protocol that sends a keep alive periodically - through the existing TCP connection.

I am struggling to understand how I can fork the JMeter 'thread group' to handle a TCP Keep alive received over the same TCP session.

Any ideas?

Thank you brainstrust!