If you have problem of connecting to CVS through ssh and non-standard port, please refer to http://michi.knallgrau.at/blog/month?date=200511

cvs -d :ext:michi@cvs.some.server.com:12345/opt/cvs co MyProject
But this results in the following error: 
CVSROOT port specification is only valid for gserver, kserver, and pserver connection methods.
According to this posting
-> http://lists.gnu.org/archive/html/info-cvs/2004-10/msg00291.html
it seems, that it is necessary to define an ssh-Alias by adding the following lines to ~/.ssh/config: 
Host SomeCvsServer
  HostKeyAlias cvs.some.server.com
  Hostname cvs.some.server.com
  Port 12345
Then the following command will be rewarded with success: 
cvs -d :ext:michi@SomeCvsServer:/opt/cvs co MyProject