Heartbeats provide (application-level) connectivity during a FIX session. The heartbeat message maintains the communication link when transactional messages (e.g. trading order routing message) are not received. Under normal conditions, the client and T4 FIX API server will interchange heartbeats at the pre-determined periodic interval (30 seconds). Heartbeats are acknowledged by the counterparty through the generation of a subsequent “echo” heartbeat.
When no message is received within the periodic interval, a heartbeat time-out condition is encountered. Thereafter, a heartbeat is sent to the non-responding party. Upon further unresponsiveness, a Test Request message follows. The requested party must respond to the Test Request message with a Heartbeat message containing the TestRequestID (Tag 112) sourced from the Test Request message. Failure to generate a heartbeat for such test request will result in a Logout with the subsequent termination of the current FIX Session.
Please note that regardless of time-out conditions, Test Requests can be sent by either party at any time. Correspondingly, a heartbeat with a TestRequestID (Tag 112) must be responded to the initiating party.
| Tag | Field Name | Req'd | Comments |
| Standard Header | Y | MsgType = 0 | |
| 112 | TestReqID | N | Required when the heartbeat is the result of a Test Request message |
| Standard Trailer | Y |
Normal Heartbeat: 34=43|49=T4Example|56=T4|50=T4FIX|52=20120905-17:54:49.359| [FIXHEARTBEAT] [MsgSeqNum] 34 = 43 [SenderCompID] 49 = T4Example [TargetCompID] 56 = T4 [SenderSubID] 50 = T4FIX [SendingTime] 52 = 20120905-17:54:49.359 A Heartbeat as a response to a Test Request: 34=123|49=T4|56=T4Example|50=TraderName|52=20120905-18:09:12.103|112=treqid.09.05.2012-13.09.12| [FIXTESTREQUEST] [MsgSeqNum] 34 = 123 [SenderCompID] 49 = T4 [TargetCompID] 56 = T4Example [SenderSubID] 50 = TraderName [SendingTime] 52 = 20120905-18:09:12.103 [TestReqID] 112 = treqid.09.05.2012-13.09.12