The fix committed in the github repo applied to the nethogs' Jessie package sources solves the problem for me, thanks.
This bug also affects Jessie kernel 3.16.0-4-amd64 #1 SMP Debian
3.16.7-ckt20-1+deb8u1 (2015-12-14) x86_64.
- Bug#808433: nethogs doesn't start, saying "creating sock... Greg Harvey
- Bug#808433: nethogs doesn't start, saying "creating... Joe Clifford