/usr/bin/rpcgen rpcgen is a tool that generates C code to implement an RPC protocol. The input to rpcgen is a language similar to C known as RPC Language (Remote Procedure Call Language).
/System/Library/PrivateFrameworks/oncrpc.framework/bin/rpcgen rpcgen is a tool that generates C code to implement an RPC protocol. The input to rpcgen is a language similar to C known as RPC Language (Remote Procedure Call Language). rpcgen is normally used as in the first synopsis where it takes an input file and generates up to four output files. If the infile is named proto.x, then rpcgen will generate a header file in proto.h, XDR routines in proto_xdr.c, server-side stubs in proto_svc.c, and client-side stubs in proto_clnt.c.
The binary is a part of oncrpc private framework.