The Heartbeat (tag 35-MsgType=0) message is sent at regular intervals to ensure that the connection between the client and CME Globex is in a normal state. The heartbeat interval is specified during logon in tag 108-HeartBtInt of the Logon (tag 35-MsgType=A) message. If either the client or CME Group does not send messages within the time defined in tag 108-HeartBtInt, then a Heartbeat message is transmitted. A Heartbeat message is also sent in response to a Test Request (tag 35-MsgType=1) message.


CME Group requires a heartbeat interval between 5 and 60 seconds. Intervals of less than 5 seconds are not permitted. Intervals longer than 60 seconds are not supported. The recommended value is 30 (seconds). 

  • Set the heartbeat interval between 30 and 60 seconds. If the client system sets the heartbeat interval to greater than 60 seconds, the client system will not be able to logon.
  • CME Globex does not generate Heartbeat messages when responding to a Resend Request. Heartbeats are not sent even in highly unusual cases when the Resend Request takes longer to process than a heartbeat interval. For additional information, see Resend Request.

The following diagram illustrates the sequence of Logon (tag 35-MsgType=A), Logon Confirm (tag 35-MsgType=A) and Test Request (tag 35-MsgType=1) messages. In addition the diagram illustrates the recommended Heartbeat (tag 35-MsgType=0) interval and assumes no other messaging activity for 60 seconds following Logon.


Heartbeat (tag 35-MsgType=0) messages can be sent at regularly defined intervals by either side in the absence of any other messaging and keeps the session alive. These Heartbeats also prevents the other side from sending Test Request (tag 35-MsgType=1) messages.

The practice of preventing the other side from sending Test Request (tag 35-MsgType=1) messages mitigates the possibility of the other side timing out and disconnecting from the uncommunicative side.