An example of registering multiple versions of a remote procedure

By convention, the first version number of program PROG is PROGVERS_ORIG and the most recent version is PROGVERS.

Suppose there is a new version of the ruser program that returns an unsigned short rather than a long. If we name this version RUSERSVERS_SHORT, then a server that wants to support both versions would do a double register. The same server handle would be used for both of these registrations.

   if (!svc_reg(transp, RUSERSPROG, RUSERSVERS_ORIG,
     nuser, nconf)) {
   	fprintf(stderr, "can't register RUSER service\n");
   	exit(1);
   }
   if (!svc_reg(transp, RUSERSPROG, RUSERSVERS_SHORT,
     nuser, nconf)) {
   	fprintf(stderr, "can't register RUSER service\n");
   	exit(1);
   }

   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 (0);
       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;
       }
       return (0);
   }