Confess to being a bit bemused by this. Mimicking a Skype message exchange is all very well, but it's obviously not going via the normal Skype server for the directory, and their location is known. Secondly, I'm not clear what the point of mimicking apache, ftp servers or openssl might be - why not run a modified version of the open source product, because you could be confident that the state machine and responses would (necessarily) be indistinguishable from the unmodified version.
