I am using nodemcu and program it in arduino ide. The serial monitor display those word that are not recognised by our human beings. i need to let my nodemcu to act asstation and access point at same time. There is no any compilation error. My nodemcu keep blinking when upload the code. Should i download any thing like i already searched for long time but i couldnt find the procedure for downloading esptool.

SO long as you have the ESP8266 boards package installed it should recognise the board.
Have you done that by adding " " to the additional boards manager URL box in preferences.

Some of those boards may also depend on a driver that is NOT included with the IDE such as the CH340 drivers available HERE

You should not need ESPTOOL as the Arduino IDE can handle these boards very well.
I only tended to use that to update the cheaper ESP's to newer firmware which you really should not need to do.