samples/net/coaps_server: Failed to send response to coaps_client

[tarunkum]

I was trying to test coaps_server along with coaps_client with two different frdm_k64f boards.
The steps I have followed for coaps_server & coaps_cleint is as below:

cd zephyr/samples/net/coaps_client
mkdir build && cd build && cmake -GNinja -DBOARD=frdm_k64f ../
ninja
cp -vr outdir/frdm_k64f/zephyr.bin /run/media/MBED/

cd zephyr/samples/net/coaps_server
mkdir build && cd build && cmake -GNinja -DBOARD=frdm_k64f ../
ninja
cp -vr outdir/frdm_k64f/zephyr.bin /run/media/MBED1/

•Here I am trying make one frdm_k64f as coaps_client & other one as coaps_server.
•I have not done any changes in prj.conf files in both sample apps.
•After flashing both codes not able to see any response from coaps server to coaps_client console.

I have tested on latest commit today.
I am getting below error on coaps_client serial window.

******* Booting Zephyr OS v1.12.0-1017-g353acf4 *****
Cannot get bind IPv6 mcast (-2)udp_init failed returned 0xffffffea**