In older Oracle Solaris releases, rpcgen created stubs that used the socket functions. With the current Oracle Solaris release, you can use either the transport-independent RPC (TI-RPC) or the transport-specific socket (TS-RPC) routines. These routines provides backward compatibility with previous releases. The default uses the TI-RPC interfaces. The –b flag tells rpcgen to create TS-RPC variant source code as its output.