SIP
416 Unsupported URI Scheme
The server cannot process the request because the URI scheme in the Request-URI is unknown to the server.
이 코드를 보게 되는 경우
When using a URI scheme (e.g., tel:, im:, pres:) that the receiving server does not support.
해결 방법
Use a supported URI scheme. Most SIP servers support sip: and sips: schemes. Check server capabilities with OPTIONS.