XTLS/Xray-core · error

failed to read request version

Error message

failed to read request version

What it means

Error "failed to read request version" thrown in XTLS/Xray-core.

Source

Thrown at proxy/vless/encoding/encoding.go:74

	if _, err := writer.Write(buffer.Bytes()); err != nil {
		return errors.New("failed to write request header").Base(err)
	}

	return nil
}

// DecodeRequestHeader decodes and returns (if successful) a RequestHeader from an input stream.
func DecodeRequestHeader(isfb bool, first *buf.Buffer, reader io.Reader, validator vless.Validator) ([]byte, *protocol.RequestHeader, *Addons, bool, error) {
	buffer := buf.StackNew()
	defer buffer.Release()

	request := new(protocol.RequestHeader)

	if isfb {
		request.Version = first.Byte(0)
	} else {
		if _, err := buffer.ReadFullFrom(reader, 1); err != nil {
			return nil, nil, nil, false, errors.New("failed to read request version").Base(err)
		}
		request.Version = buffer.Byte(0)
	}

	switch request.Version {
	case 0:

		var id [16]byte

		if isfb {
			copy(id[:], first.BytesRange(1, 17))
		} else {
			buffer.Clear()
			if _, err := buffer.ReadFullFrom(reader, 16); err != nil {
				return nil, nil, nil, false, errors.New("failed to read request user id").Base(err)
			}
			copy(id[:], buffer.Bytes())
		}

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at proxy/vless/encoding/encoding.go:74 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/d2ee7387590125f2. Report an issue: GitHub.