What does errno 104 (EBADMSG) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A UCRT POSIX compatibility errno for a message that fails the receiving interface's expected format or validation.

Could be also:
Constant	Type	OS
ERROR_INVALID_AT_INTERRUPT_TIME	Win32 error	Windows
ECONNRESET	errno	Linux
ENOTRECOVERABLE	errno	Mac
FILE_INITIALIZATION_FAILED	BugCheck Code	Windows

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ENOTRECOVERABLE	ENOBUFS

EBADMSG

EBADMSG is defined by the UCRT as a POSIX compatibility constant. It describes a message that reached a receiving interface but could not be accepted as a valid message for that interface. The value by itself does not identify a Win32 API, a Winsock call, or a particular wire protocol.

For a decoder, queue adapter, RPC layer, or portability library, the important boundary is usually between received bytes and accepted message. A frame can be present yet still fail a length check, a required-field check, a checksum or signature check, a type discriminator, or a version-specific rule.

Useful evidence to keep

The API or library that produced EBADMSG, its return value, and the error value captured immediately afterwards.
The protocol stage, expected message type or version, declared length, and validation rule that rejected the input.
A bounded, redacted representation of the header or message metadata when it is safe to retain it.

EBADMSG concerns one unacceptable message. It should not be treated as a synonym for a lost connection or for the broader protocol-state failure represented by EPROTO.

References

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