code: private static ByteBuf writePayload(
  			final ByteBufAllocator alloc,
  			final long requestId,
  			final MessageType messageType,
  			final byte[] payload) {
  
  		final int frameLength = HEADER_LENGTH + REQUEST_ID_SIZE + payload.length;
  		final ByteBuf buf = alloc.ioBuffer(frameLength + Integer.BYTES);
  
  		buf.writeInt(frameLength);
  		writeHeader(buf, messageType);
  		buf.writeLong(requestId);
  		buf.writeBytes(payload);
  		return buf;
  	}
docs: Helper for serializing the messages.
  
  @param alloc			The {@link ByteBufAllocator} used to allocate the buffer to serialize the message into.
  @param requestId		The id of the request to which the message refers to.
  @param messageType	The {@link MessageType type of the message}.
  @param payload		The serialized version of the message.
  @return A {@link ByteBuf} containing the serialized message.