Bottom Level Interface

The bottom-level interface to RPC lets the application control all options. clnt_tli_create() and the other expert-level RPC interface routines are based on these routines. You rarely use these low-level routines.

Bottom-level routines create internal data structures, buffer management, RPC headers, and so on. Callers of these routines, like the expert level routine clnt_tli_create(), must initialize the cl_netid and cl_tp fields in the client handle. For a created handle, cl_netid is the network identifier (for example udp) of the transport and cl_tp is the device name of that transport (for example /dev/udp). The routines clnt_dg_create() and clnt_vc_create() set the clnt_ops and cl_private fields.

Client

Example 4-14 shows calls to clnt_vc_create() and clnt_dg_create().

Example 4-14 Client for Bottom Level

/*
 * variables are:
 * cl: CLIENT *
 * tinfo: struct t_info returned from either t_open or t_getinfo
 * svcaddr: struct netbuf *
 */
	switch(tinfo.servtype) {
		case T_COTS:
		case T_COTS_ORD:
			cl = clnt_vc_create(fd, svcaddr,
			 prog, vers, sendsz, recvsz);
			break;
		case T_CLTS:
			cl = clnt_dg_create(fd, svcaddr,
			 prog, vers, sendsz, recvsz);
			break;
		default:
			goto err;
	}

These routines require that the file descriptor is open and bound. svcaddr is the address of the server.

Server

Example 4-15 is an example of creating a bottom-level server.

Example 4-15 Server for Bottom Level

/*
 * variables are:
 * xprt: SVCXPRT *
 */
switch(tinfo.servtype) {
	case T_COTS_ORD:
	case T_COTS:
		xprt = svc_vc_create(fd, sendsz, recvsz);

		break;
	case T_CLTS:
		xprt = svc_dg_create(fd, sendsz, recvsz);

		break;
	default:
		goto err;
}