XTLS/Xray-core · error

failed to read packet length

Error message

failed to read packet length

What it means

Error "failed to read packet length" thrown in XTLS/Xray-core.

Source

Thrown at proxy/vless/encoding/addons.go:173

	}
	return nil
}

func NewLengthPacketReader(reader io.Reader) *LengthPacketReader {
	return &LengthPacketReader{
		Reader: reader,
		cache:  make([]byte, 2),
	}
}

type LengthPacketReader struct {
	io.Reader
	cache []byte
}

func (r *LengthPacketReader) ReadMultiBuffer() (buf.MultiBuffer, error) {
	if _, err := io.ReadFull(r.Reader, r.cache); err != nil { // maybe EOF
		return nil, errors.New("failed to read packet length").Base(err)
	}
	length := int32(r.cache[0])<<8 | int32(r.cache[1])
	// fmt.Println("Read", length)
	mb := make(buf.MultiBuffer, 0, length/buf.Size+1)
	for length > 0 {
		size := length
		if size > buf.Size {
			size = buf.Size
		}
		length -= size
		b := buf.New()
		if _, err := b.ReadFullFrom(r.Reader, size); err != nil {
			return nil, errors.New("failed to read packet payload").Base(err)
		}
		mb = append(mb, b)
	}
	return mb, nil
}

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at proxy/vless/encoding/addons.go:173 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/1e06eabf0bcd2ed3. Report an issue: GitHub.