This message will be there since the setting under [network] in file /etc/rbfeeder.ini are as follows, but there is no dump1090 running to provide data on port 30005
[network]
mode=beast
external_port=30005
external_host=127.0.0.1
You may either ignore it, or change "external_port=30005" to "external_port=30979". This may or may not work. Try it, if it creates problem, change port number back to 30005.
Dont forget to save file then restart rbfeeder after every time you make a change in file /etc/rbfeeder.ini