Class: FrameReader

Stateful MLLP frame decoder. Feed raw TCP byte chunks via push(chunk). Complete frames fire synchronously via onFrame callback during push().

The decoder operates as a 3-state FSM:

• SCANNING_FOR_VT, waiting for the 0x0B frame-start byte
• READING_PAYLOAD, accumulating payload bytes until FS (0x1C)
• EXPECTING_CR, received FS, waiting for CR (0x0D) to complete the frame

Example

const reader = new FrameReader({
  onFrame: (payload, byteOffset, warnings) => process(payload, byteOffset, warnings),
  onWarning: (w) => logger.warn(w),
});
socket.on('data', (chunk) => reader.push(chunk));

Constructors

Constructor

new FrameReader(opts): FrameReader

Construct a chunked MLLP frame reader.

Parameters

opts

FrameReaderOptions

Reader options (onFrame/onWarning callbacks, tolerance, maxFrameSizeBytes).

Returns

FrameReader

Methods

push()

push(chunk): void

Feed a chunk of raw TCP bytes into the FSM. Frames fire synchronously via onFrame during this call. May throw MllpFramingError for unrecoverable framing violations when the matching tolerance is not enabled.

Parameters

chunk

Buffer

Returns

void

Example

socket.on('data', (chunk) => reader.push(chunk));

---

reset()

reset(): void

Clear internal accumulator state and reset byte offset to 0.

Call on reconnect / connection reuse to start fresh without allocating a new reader. Pending partial frame state is discarded silently.

Returns

void

Example

socket.on('close', () => reader.reset());