OnWeb Web to Host version 6.9.3 has been enhanced with the ability to configure Client Side Keep Alive for mainframe sessions. 

The host wizard has been changed to allow for the properties 'KeepAliveMode' (System = Host, NOP = Client) and 'NOPInterval' (the time in seconds). 

If configured they are added to the mainframe html session.  The procontainerfunc.js reads these values from the html session and assigns them to the telnet interface properties. 

Contact Micro Focus Customer Support for the most current Web to Host hotfix - they’re cumulative, so this will include the service pack as well.