SIP 204 No Notification vs 481 Call/Transaction Does Not Exist
SIP 204 (No Notification) is a 2xx Success response, while 481 (Call/Transaction Does Not Exist) is a 4xx Client Failure response. 204 indicates that the request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request. In contrast, 481 means that the UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
描述
The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
何时出现
When subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
如何修复
No fix needed. The subscription was accepted but there is no state change to notify about yet.
描述
The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
何时出现
When sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
如何修复
The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.
主要区别
204 is a 2xx Success response, while 481 is a 4xx Client Failure response.
SIP 204: The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.
SIP 481: The UAS received a request that does not match any existing dialog or transaction. The call state may have been lost.
You encounter 204 when when subscribing to event packages that may not generate immediate notifications, such as dialog or presence packages.
You encounter 481 when when sending a BYE, re-INVITE, or UPDATE for a call that the server has no record of. Common after server restarts.
何时使用哪个
For 204 (No Notification): No fix needed. The subscription was accepted but there is no state change to notify about yet. For 481 (Call/Transaction Does Not Exist): The dialog has been lost. Terminate the local call state. For re-INVITE failures, re-establish the call from scratch.