489
SIP
489 Bad Event
The server did not understand the event package specified in the Event header of a SUBSCRIBE request.
เมื่อคุณพบรหัสนี้
When subscribing to an event package that the server does not support (e.g., dialog, presence, message-summary).
วิธีแก้ไข
Check which event packages the server supports (OPTIONS request) and use a supported event package name.