Connecting Multiple ESP-12E with the help of router

Hi every one!

I am connecting two ESP-12E with the help of router. when both are connected to same router, I can do communication between ESPs using their IPs(Using UDP) when router has access to internet. but as I disconnect internet cable from router and router got disconnected from internet, then I can't do communication between ESPs although they are connected with router. kindly direct me what is the problem.
thanks in advance.

try

  1. Wireshark to monitor the network traffic (you should see you UDP datagrams)
  2. login to the router to check that it lists the ESP-12E devices

this may give you some idea what is the problem

thanks horace fro quick response. kindly briefly describe how to monitor network traffic using Wireshark because I am using this tool for the first time and in network discovery both the devices are present means connected with router.

do a web search for Wireshark tutorials you will find plenty of help
using Wireshark you can see the packets flowing thru the network and look at the types and the conetents
in a busy network you will see dozens of packets a second so you can set up filters to examine packets based on type, source/destination IP address, etc