rlogin/rsh incoming port

Hi all,

In need to know why my sample code below that connect to a rlogind (513) fails, but original unix rlogin does not ? (.rhosts is verified to be correct)

I heard rlogin/rsh bind to a reserved port before connecting to the rlogin server. what are they ???

   s = socket(AF_INET, SOCK_STREAM, 0);
   sck.sin_family      = AF_INET;
   sck.sin_port        = htons(513);
   sck.sin_addr.s_addr = inet_addr("192.168.15.40");

   if (connect(s, (struct sockaddr *)&sck,sizeof(sck)) <0) {
      printf("connect() error\n"); return;
   }
   printf("Connected %d\n",s);
   write(s,"",1);
   write(s,"root",5);
   write(s,"root",5);
   write(s,"linux/38400",12);

   read(s,buf,sizeof(buf));
   printf("%s\n",buf);

Any help would be appreciated

rlogin is suid to root. So it can rcmd() and the associated routines on the rcmd man page. That includes rresvport(). See those man pages. User program can use rexec() which also has a man page.