text: NL = b'\n'
  DATA_SIZE = 4
  FRAME_SIZE = 4
  HEADER_SIZE = DATA_SIZE + FRAME_SIZE
  MAX_CHUNK_SIZE = 65536
  
  TIMESTAMP_SIZE = 8
  ATTEMPTS_SIZE = 2
  MSG_ID_SIZE = 16
  MSG_HEADER = TIMESTAMP_SIZE + ATTEMPTS_SIZE + MSG_ID_SIZE
  MAX_CHUNK_SIZE = 65
  
  FRAME_TYPE_RESPONSE = 0
  FRAME_TYPE_ERROR = 1
  FRAME_TYPE_MESSAGE = 2
  MAGIC_V2 = b'  V2'
  
  HEARTBEAT = b'_heartbeat_'
  PULSE = b'NOP\n'
  BIN_OK = b'\x00\x00\x00\x06\x00\x00\x00\x00OK'
  
  # nsq TCP commands
  FIN = b'FIN'
  REQ = b'REQ'
  TOUCH = b'TOUCH'
  RDY = b'RDY'
  MPUB = b'MPUB'
  CLS = b'CLS'
  AUTH = b'AUTH'
  SUB = b'SUB'
  PUB = b'PUB'
  
  # connection status
  CLOSED = 0
  INIT = 1
  CONNECTED = 2
  SUBSCRIBED = 3
  