I have recently released Logtilla, a framework for parsing and analysing web access log files, and showed in a previous article how to use Logtilla with a simple example. One of the most interesting aspects of Logtilla is in the inside. Logtilla demonstrates how to use ASN.1 to communicate between an Erlang program and a C port program. This article is both an introduction to the usual concepts of ASN.1, and a tutorial to apply ASN.1 to integrate Erlang and C programs. The protocol defined in Logtilla is simple, but the approach described can be used to implement sophisticated distributed protocols, especially appropriate for systems management applications.