docs: def add_tcp_callback(self, port, callback, threaded_callback=False):
          """
          Adds a unix socket server callback, which will be invoked when values
          arrive from a connected socket client. The callback must accept two
          parameters, eg. ``def callback(socket, msg)``.
          """
          if not callback:
              raise AttributeError("No callback")
  
          serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
          serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
          serversocket.bind((_TCP_SOCKET_HOST, port))
          serversocket.listen(1)
          serversocket.setblocking(0)
          self._epoll.register(serversocket.fileno(), select.EPOLLIN)
  
          # Prepare the callback (wrap in Thread if needed)
          cb = callback if not threaded_callback else \
                  partial(_threaded_callback, callback)
  
          self._tcp_server_sockets[serversocket.fileno()] = (serversocket, cb)
          debug("Socket server started at port %s and callback added." % port)