0 What is Heartbeat Extension? OpenSSL introduced an extension Heartbeat to keep the session alive for a longer time and to avoid reestablishment of sessions. Heartbeat introduced in OpenSSL with its 1.0.1 build release as defined in the RFC 6520 TLS/DTLS Heartbeat Extension. Heartbeat messages can be sent without authenticating with the server. For every request, there might be a Heartbeat request and a Heartbeat response.