// After the association is established, a Heartbeat is expected and answered.

+0  socket(..., SOCK_STREAM, IPPROTO_SCTP) = 3
+0  connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
+0  > sctp: INIT[flgs=0, tag=..., a_rwnd=..., os=..., is=..., tsn=1, ...]
+0.05  < sctp: INIT_ACK[flgs=0, tag=22, a_rwnd=100000, os=2048, is=10, tsn=1, STATE_COOKIE[len=4, val=...]]
+0  > sctp: COOKIE_ECHO[flgs=0, len=4, val=...]
+0.05  < sctp: COOKIE_ACK[flgs=0]

+30 ~ +35 > sctp: HEARTBEAT[flgs=0, HEARTBEAT_INFORMATION[len=..., val=...]]
+0.05 < sctp: HEARTBEAT_ACK[flgs=0, HEARTBEAT_INFORMATION[len=..., val=...]]
+1  close(3) = 0
+0  > sctp: SHUTDOWN[flgs=0, cum_tsn=0]
+0.05  < sctp: SHUTDOWN_ACK[flgs=0]
+0  > sctp: SHUTDOWN_COMPLETE[flgs=0]

