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.