ultrix man page for rresvport

rcmd(3x)																  rcmd(3x)

Name
       rcmd, rresvport, ruserok - routines for returning a stream to a remote command

Syntax
       rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);
       char **ahost;
       u_short inport;
       char *locuser, *remuser, *cmd;
       int *fd2p;

       s = rresvport(port);
       int *port;

       ruserok(rhost, superuser, ruser, luser)
       char *rhost;
       int superuser;
       char *ruser, *luser;

Description
       The subroutine is used by the superuser to execute a command on a remote machine using an authentication scheme based on reserved port num-
       bers.  The subroutine is a routine that returns a descriptor to a socket with an address in the privileged port space.  The subroutine is a
       routine	used  by  servers to authenticate clients requesting service with All three functions are present in the same file and are used by
       the server (among others).

       The subroutine looks up the host *ahost using returning -1 if the host does not exist.  For further information, see  Otherwise	*ahost	is
       set to the standard name of the host and a connection is established to a server residing at the well-known Internet port inport.

       If  the call succeeds, a socket of type SOCK_STREAM is returned to the caller and given to the remote command as stdin and stdout.  If fd2p
       is nonzero, then an auxiliary channel to a control process will be set up, and a descriptor for it will be placed in  *fd2p.   The  control
       process	will  return diagnostic output from the command (unit 2) on this channel, and will also accept bytes on this channel as being UNIX
       signal numbers, to be forwarded to the process group of the command.  If fd2p is 0, then the stderr (unit 2 of the remote command) will	be
       made  the  same as the stdout and no provision is made for sending arbitrary signals to the remote process, although you may be able to get
       its attention by using out-of-band data.

       The protocol is described in detail in

       The subroutine is used to obtain a socket with a privileged address bound to it.  This socket is suitable for use by and several other rou-
       tines.	Privileged addresses consist of a port in the range 0 to 1023.	Only the superuser is allowed to bind an address of this sort to a
       socket.

       The subroutine takes a remote host's name, as returned by a routine, two user names and a flag indicating if the local user's name  is  the
       superuser.  It then checks the files and in the user's home directory to see if the request for service is allowed.  A 0 is returned if the
       machine name is listed in the file, or the host and remote user name are found in the file.  Otherwise returns -1.  If the  superuser  flag
       is 1, the checking of the file is bypassed.

See Also
       rlogin(1c), rsh(1c), gethostent(3n), rexec(3x), rexecd(8c), rlogind(8c), rshd(8c)

																	  rcmd(3x)