(see setting description format info here)
| Function: | Defines which UDP port the DS will send I/O line status change notifications to |
| Post-initialization value: | 0 (last known port) |
| Change takes effect: | After reboot |
| First introduced: | Earlier than "baseline" V3.14/V3.51 |
Notification (J) messages are generated when one of the monitored I/O lines of the DS changes its state. Which I/O lines are monitored for changes is defined by the Notification Bitmask (NB) setting . Notifications are only sent when the data connection is established and are sent to the network host with which this connection is established. Notification Destination defines which UDP port on the destination host notifications are sent to when notifications are being sent as UDP datagrams (out-of-band ):
| 0 (last known port) | Notifications are sent to the UDP port from which the most recent programming UDP datagram was received. Therefore, notifications are sent after at least one such datagram is received (since the data connection is established). This option is useful when the DS has to send notifications to the PC. Port number from which PC applications are sending their programming UDP datagrams are usually ephemeral which means that they are always changing. Therefore, the DS will wait for the first programming UDP datagram to arrive. |
| 1 (port 65535) | Notifications are always sent to the UDP port 65535. This option is useful when the DS is communicating with another DS. In this case the port to send notifications to is fixed and known so there is no need to wait for the programming UDP datagram to arrive. |
Notification Destination is irrelevant when the Notification Bitmask (NB) is set to is 0 because this means that no I/O lines of the DS are monitored for changes (so there will be no notifications to generate). Notification Destination is also irrelevant when notifications are being sent inside the data TCP connection itself (see Notification (J) message for more information on when this happens).