By convention, the first version number of the PROG program is referred to as PROGVERS_ORIG, and the most recent version is PROGVERS. For example, the programmer can create a new version of the user program that returns an unsigned short value rather than a long value. If the programmer names this version RUSERSVERS_SHORT, then the following program permits the server to support both programs:
if (!svc_register(transp, RUSERSPROG, RUSERSVERS_ORIG,
nuser, IPPROTO_TCP)) {
fprintf(stderr, "can't register RUSER service\n");
exit(1);
}
if (!svc_register(transp, RUSERSPROG, RUSERSVERS_SHORT,
nuser, IPPROTO_TCP)) {
fprintf(stderr, "can't register RUSER service\n");
exit(1);
}
Both versions can be handled by the same C procedure, as in the following example using the nusers procedure:
nuser(rqstp, transp)
struct svc_req *rqstp;
SVCXPRT *transp;
{
unsigned long nusers;
unsigned short nusers2;
switch (rqstp->rq_proc) {
case NULLPROC:
if (!svc_sendreply(transp, xdr_void, 0)) {
fprintf(stderr, "can't reply to RPC call\n");
return (1);
}
return;
case RUSERSPROC_NUM:
/*
* Code here to compute the number of users
* and assign it to the variable nusers
*/
nusers2 = nusers;
switch (rqstp->rq_vers) {
case RUSERSVERS_ORIG:
if (!svc_sendreply(transp, xdr_u_long,
&nusers)) {
fprintf(stderr,"can't reply to RPC call\n");
}
break;
case RUSERSVERS_SHORT:
if (!svc_sendreply(transp, xdr_u_short,
&nusers2)) {
fprintf(stderr,"can't reply to RPC call\n");
}
break;
}
default:
svcerr_noproc(transp);
return;
}
}