-c can't reach all servers listed on a built-in directory

[mcfnord]

As @rdica mentions here, the -c command line option can't reach every server listed on a built-in directory. In fact, most servers might not be reachable using -c, because most clients rely on a "hole punch" procedure to reach a server without the server explicitly opening the port.

This probably merits mentioning in the command-line documentation for this feature.