message: request more bytes at a time when reading JSON
diff: @@ -319,7 +319,7 @@ class Channel(PacketSink):
  # TODO: handle device that could (maliciously) send infinite stream
  buffer = bytes()
  while True:
  - chunk_length = 64
  + chunk_length = 512
  chunk = self.remote_endpoint_operation(endpoint_id, struct.pack("<I", len(buffer)), True, chunk_length)
  if (len(chunk) == 0):
  break
  