[ibr-dtn] ERror IPNDAgent join failed

Hello,

i have a problem with my ibr-dtn, i will be very glad if someone could help me to fix this.

i have ibrdtn instaled on my raspberry pi and ubuntu. with the same configuration. when i run ibrdtn on ubuntu there aren't any error message and it can transfered file

but when i run ibrdtn on my raspberry pi using command dtnd -i wlan0 -c /etc/ibrdtn/ibrdtn.conf -v it says error message : "ERROR IPNDAgent: join failed on wlan0; 92: setsockopt() but it still can transfered file but cannot ping to another node

what's that mean? and how to fixed it?

thank you :)