The Test Request<1> message is utilized to force a heartbeat from the opposing application. The Test Request<1> message is useful for checking sequence numbers or verifying communication line status. The opposite application will respond to the Test Request<1> with a Heartbeat<0> containing the TestReqID(112).
The TestReqID(112) is used to verify that the opposite application is generating the heartbeat as the result of Test Request<1> and not a normal timeout. The opposite application will include the TestReqID(112) in the resulting Heartbeat<0>. Any string can be used as the TestReqID(112) (one suggestion is to use a timestamp string).
The '^' character is used to represent SOH character.