at first a quote from enhanced-ctorrent user's guide:
so the -p option can work.-p port Listen port. (default 2706 -> 2106)
Specify the TCP port number on which to listen for incoming connections. By default, CTorrent starts at 2706 and searches for an available port in decreasing order until it finds one or exhausts all ports down through 2106. The behavior with this option is similar, but starting at the specified port number.
there is no confusion between the two -p options
you can start dctcs like:
dctcs --ctorrent-args "-p 6881"
or
dctcs -- -p 6881
or you can set in the config file:
ctorrent-args=-p 6881