Dialog states
A dialog can assume several states. The dialog state is present in the $DLG_status variable. The values can be as follows:
NULL: Not found1: Unconfirmed (INVITE sent but no reply received)2: Early state (INVITE sent and provisional reply received, 100,180,183)3: Confirmed (INVITE sent, 200 OK received, no ACK)4: Established (INVITE sent, 200 OK received, ACK confirmed)5: Ended (BYE received)
It is very useful to check the dialog state before taking any action such as reading dialog variables. If the dialog is NULL, a dialog variable and/or flag is not readable.
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