CodeCenter version 4.x (ObjectCenter 2.x) includes the communication server clms_registry, which should be installed during the normal CodeCenter installation. This program must be running in order for Builder Xcessory and CodeCenter to communicate.
Note: Problems running CodeCenter from Builder Xcessory are likely due to the Builder Xcessory execution of CodeCenter. To work around this, start CodeCenter on the same machine from another xterm (exiting Builder Xcessory is unnecessary), and connect to it from Builder Xcessory.