class_docstr: Base asynchronize message handler.
  
  The tracker and client follows a simple message protocol.
  The message is in form [nbytes(int32)] [json-str].
  All the information is packed in json-str
code: def __init__(self, tracker, sock, addr):
      super(TCPEventHandler, self).__init__(sock)
      self._data = bytearray()
      self._tracker = tracker
      self._msg_size = 0
      self._addr = addr
      self._init_req_nbytes = 4
      self._info = {}
      # list of pending match keys that has not been used.
      self.pending_matchkeys = set()
      self._tracker._connections.add(self)
      self.put_values = []
  
imports: import asyncio
  import heapq
  import logging
  import socket
  import threading
  import errno
  import struct
  import json
  from tvm.contrib.popen_pool import PopenWorker
  from .._ffi.base import py_str
  from .None import base
  from .base import RPC_TRACKER_MAGIC, TrackerCode
label_desc: Use image node_id 1 to create a new TCPEventHandler object from inherited base classes: tornado_util with example: obj = TCPEventHandler(tracker, sock, addr)