What does HRESULT 0x80EF01F5 (RTC_E_STATUS_SERVER_NOT_IMPLEMENTED) mean?

RTC_E_STATUS_SERVER_NOT_IMPLEMENTED

Operational meaning: RTC_E_STATUS_SERVER_NOT_IMPLEMENTED

The useful interpretation of this result is narrower than “SIP error”; within a peer, proxy, registrar, or gateway returning a specific SIP response to the RTC transaction, it means the server does not implement the SIP method needed.

The stored value is 0x80EF01F5 in the RTC SIP-status facility carrying status 501; keep both forms in telemetry so COM error wrapping does not erase whether RTC produced an interface result, mapped a SIP response, or surfaced a PINT outcome.

Collect enough state to capture method, Server/User-Agent identity, Allow and Supported headers, and target role; the result evidence should demonstrate why Not Implemented is server-wide method capability; 405 means the method is disallowed for a particular resource.

Signals worth preserving

Capture the first result before retry, reconnect, profile re-enable, or teardown changes the evidence; associate this result with one RTC object instance and one transaction or media transition.

• Code-specific proof: capture method, Server/User-Agent identity, Allow and Supported headers, and target role.
• Correlation key: Call-ID/CSeq/tags.
• Protocol or object snapshot: status-specific headers.
• Last completed transition: retry or alternate-target decision.
• Expected output: request method and Request-URI.

Recovery and control flow

The owning RTC component should use a supported feature path or different capable endpoint rather than repeating the same method; it should also settle or cancel its previous operation before callers begin a replacement.

Before retrying this result, classify the previous operation as definitely failed, definitely completed, or remotely uncertain; that distinction prevents duplicate dialogs, bindings, transfers, or roaming mutations.

Example: A legacy proxy receives a REFER method it does not implement.

Protocol and object state

Verification workflow

1. Record it and 0x80EF01F5 at the first RTC method or event that returns it.
2. Prove the condition by ensuring the trace can capture method, Server/User-Agent identity, Allow and Supported headers, and target role.
3. Apply one controlled change: use a supported feature path or different capable endpoint rather than repeating the same method; then verify the result return value and resulting RTC state.

Actions that do not address this condition

• Do not show a reason phrase as trusted server identity or authorization evidence.
• Do not retry every 4xx or 5xx response with the identical request.

Do not confuse it with

For this HRESULT, 405 can occur even when the server implements that method elsewhere; the neighboring results below require different control-flow decisions.

Technical references

• Microsoft RTC return constants.
• SIP response semantics.