I am using Arduino IDE to program my ESP8266. I would like to send data from one ESP8266 module to other. So I would like to use CoAP for this communication. Is there any standard or good library to implement CoAP in ESP8266.
There are no standards only RFCs for CoAP; all of them are accessible on the web:
I think you were looking for this. I use this library for my arduino projects on a Wemos esp8266 based board.