/usr/bin/diameterc is in erlang-diameter 1:17.3-dfsg-4+deb8u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../lib/erlang/lib/diameter-1.7.1/bin/diameterc
/usr/bin/../lib/erlang/lib/diameter-1.7.1/bin/diameterc