C CA_SERVER_PORT (caProto.h) — const-derived from the generated
ENV_PARAM table, so it cannot drift from configure/CONFIG_ENV. A default
that stopped being a valid port would fail const-evaluation.
Client-side CA server-port reader — where to send SEARCH.
Honours EPICS_CA_SERVER_PORT only; the server-only
EPICS_CAS_SERVER_PORT does not affect client behaviour.
Server-side CA bind-port reader — where the server binds the
UDP discovery socket and the TCP listener (same value for both,
matching caservertask.c:491-499 —
ca_udp_port = ca_server_port).