You can specify Host and Port to connect to TCP console of the Accel-ppp server. Just change values in the <Module "accel-ppp"=""> block:
<Module "accel-ppp"> Server "127.0.0.1:2001" </Module>
Accel-ppp TCP console address is 127.0.0.1:2001 by default.
There will be accel-ppp directory in collectd BaseDir/rrd/your host/ contains some RRD files: