TooTallNate/Java-WebSocket · error · IllegalStateException

Size representation not supported/specified

Error message

Size representation not supported/specified

What it means

createByteBufferFromFramedata writes the frame length using 7/16/64-bit representations; the computed sizebytes value must be 0, 2, or 8. Any other value means an internal inconsistency (invalid payload length) and the code throws this IllegalStateException before the frame can be serialized.

Solutions

1. Ensure the payload ByteBuffer has a non-negative, RFC-valid remaining() size before createBinaryFrame
2. Do not manually mutate frame length fields; build frames via the library APIs (send, continuousFrame)
3. Check that total message sizes stay within 64-bit unsigned length limits
4. Catch/inspect in a debugger to find where the bad length originates

Example fix

// before
frame.setPayload(ByteBuffer.allocate(-1));
// after
frame.setPayload(ByteBuffer.allocate(payloadSize)); // payloadSize >= 0

private static boolean isEncodableLength(ByteBuffer payload) {
  return payload != null && payload.remaining() >= 0;
}
// call before createBinaryFrame: if (!isEncodableLength(payload)) skip;

boolean isEncodableLength(ByteBuffer b) { return b != null && b.remaining() >= 0; }

try {
  ws.send(payload);
} catch (IllegalStateException e) {
  if ("Size representation not supported/specified".equals(e.getMessage()))
    logger.error("Frame length cannot be encoded — payload buffer corrupted");
}

When it happens

Trigger: Attempting to serialize a frame whose payload length does not map to a supported length encoding, usually via createBinaryFrame on a frame built with a corrupted or out-of-range length (negative payload or length overflow beyond 64-bit representation).

Common situations: Custom Draft/subclass code building frames with hand-set payload lengths, payload ByteBuffers with negative remaining(), constructing frames with sizes outside RFC 6455 bounds.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Only Opcode.BINARY or Opcode.TEXT are allowed
• 1002
• buffer size < 0
• parameter must not be null
• Invalid SSL status:

AI-assisted analysis of TooTallNate/Java-WebSocket@afeacbf8c0 (2026-09-09). Data as JSON: /api/errors/246eeb6e2b70fa7a. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/org/java_websocket/drafts/Draft_6455.java:509

      one |= getRSVByte(2);
    }
    if (framedata.isRSV3()) {
      one |= getRSVByte(3);
    }
    buf.put(one);
    byte[] payloadlengthbytes = toByteArray(mes.remaining(), sizebytes);
    assert (payloadlengthbytes.length == sizebytes);

    if (sizebytes == 1) {
      buf.put((byte) (payloadlengthbytes[0] | getMaskByte(mask)));
    } else if (sizebytes == 2) {
      buf.put((byte) ((byte) 126 | getMaskByte(mask)));
      buf.put(payloadlengthbytes);
    } else if (sizebytes == 8) {
      buf.put((byte) ((byte) 127 | getMaskByte(mask)));
      buf.put(payloadlengthbytes);
    } else {
      throw new IllegalStateException("Size representation not supported/specified");
    }
    if (mask) {
      ByteBuffer maskkey = ByteBuffer.allocate(4);
      maskkey.putInt(reuseableRandom.nextInt());
      buf.put(maskkey.array());
      for (int i = 0; mes.hasRemaining(); i++) {
        buf.put((byte) (mes.get() ^ maskkey.get(i % 4)));
      }
    } else {
      buf.put(mes);
      //Reset the position of the bytebuffer e.g. for additional use
      mes.flip();
    }
    assert (buf.remaining() == 0) : buf.remaining();
    buf.flip();
    return buf;
  }

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