Heartbeat Messages

The Sequenced Unit Header with a count field set to 0 will be used for heartbeat messages. During trading hours heartbeat messages will be sent from all multicast addresses if no data has been delivered within 1 second. Heartbeat messages never increment the sequence number for a unit.

Outside of trading hours Cboe sends heartbeat messages on all real-time channels with a sequence of 0 to help users validate multicast connectivity. Heartbeat messages may not be sent from 12:00 am - 1:00 am ET or during maintenance windows.