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CO_E_OBJNOTCONNECTED
Meaning
Windows documents CO_E_OBJNOTCONNECTED as “Object is not connected to server”. In practical terms, it is returned when a COM interface proxy or object reference no longer has a usable connection to its server object.
Where the failure belongs
This result belongs to COM activation and object lifetime. COM activation is a sequence rather than one registry lookup: identifier resolution, class registration, module or process start, class-factory publication, marshaling, and object lifetime can fail independently. The relevant condition is that a COM interface proxy or object reference no longer has a usable connection to its server object.
Evidence to collect
- Capture 1: server process exit code and disconnect time.
- Capture 2: object identity, marshaling path, apartment and last successful call.
- Capture 3: RPC and application logs around release, shutdown or network interruption.
Likely causes
- Possible cause 1: the out-of-process server exited or disconnected the object.
- Possible cause 2: the client retained an interface beyond the server-defined lifetime.
- Possible cause 3: RPC connectivity or apartment teardown invalidated the proxy.
Diagnostic sequence
- Confirm that the observed path matches this condition: a COM interface proxy or object reference no longer has a usable connection to its server object.
Practical scenario
A background COM server restarts during an upgrade while a client keeps a cached proxy; reacquiring the component after restart avoids it.
Correct handling and retry
- Corrective action 1: reacquire a fresh object through the supported activation or discovery path.
- Corrective action 2: correct lifetime ownership so clients release stale interfaces promptly.
- Corrective action 3: make server restarts visible and invalidate cached proxies deterministically.
Retry guidance. Retry by creating a new object only when the operation is safe to repeat; calling the same disconnected interface again is not recovery. When retrying, avoid launch duplicate servers, reuse stale proxies or repeat an activation whose side effects are unknown.
Difference from nearby HRESULTs
CO_E_RELEASED usually indicates use after object release, while it emphasizes that the object reference is no longer connected to its server.
Developer and operational guidance
Official Microsoft references
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