An iRule event triggered when a client has established a connection.
In effect, when an entry is inserted in the BIG-IP connection table, this event fires. For TCP connections, this happens when the three-way handshake successfully completes for a Standard virtual server. For a FastL4 virtual server, this event fires on the initial syn packet.
For non-TCP connections, this will fire at a point that may not be wholly intuitive. For example, UDP is connectionless, so one might reasonably expect this event to fire with each segment in a UDP stream. However, BIG-IP does create a connection table entry for UDP, and assigns a timeout. If no segment arrives matching the table entry within the timeout period, the entry is removed (and CLIENT_CLOSED fires). However, segments matching the table entry that arrive within the timeout period will not trigger a new CLIENT_ACCEPTED event (and will reset the timeout timer for the entry). The timeout is generally configured, in the case of UDP, via the UDP profile (or a child profile) applied to the virtual server.
Some profile settings may also have an effect on when events are raised. For example, the “Datagram LB” setting on the UDP profile will force each segment in a UDP stream (that is, packets carrying UDP segments that all have a common source ip/port and destination ip/port) to load-balance. Between the BIG-IP system and the pool members, the forwarded segments will use different source port numbers for each segment (sort of like SNAT, but just for the port). In this case, CLIENT_ACCEPTED will fire for each segment. This is actually a specific case of the more general rule above, as each segment essentially creates an independent connection table entry. Notice, for example, that CLIENT_CLOSED will still fire for each segment after the timeout period.
Behavior for this command also depends on the type of virtual server. For example, a using “Standard” virtual server the event fires after the final client ACK of the three-way-handshake (as described above), on a “Performance L4” virtual server it fires on the initial SYN packet from the client.


  set curtime [clock seconds]
  set formattedtime [clock format $curtime -format {%H:%S} ]
  log "the time is: $formattedtime"