RPC routines allow C programs to make procedure calls on other machines across the network. First, the client calls a procedure to send a request to the server. Upon receipt of the request, the server calls a dispatch routine to perform the requested service, and then sends back a reply. Finally, the procedure call returns to the client.
The clnt_call(), callrpc() and clnt_broadcast() routines handle the client side of the procedure call. The remaining routines deal with error handling in the case of errors.
The CLIENT data structure is defined in the RPC/XDR Library Definition of the [a manual with the abbreviation NETP].
#include <rpc/rpc.h>
int callrpc(host, prognum, versnum, procnum, inproc, in, outproc, out) char *host; u_long prognum, versnum, procnum; char *in; xdrproc_t inproc; char *out; xdrproc_t outproc;
Call the remote procedure associated with prognum, versnum, and procnum on the machine, host. The parameter in is the address of the procedure's argument, and out is the address of where to place the result; inproc is an XDR function used to encode the procedure's parameters, and outproc is an XDR function used to decode the procedure's results. This routine returns 0 if it succeeds, or the value of enum clnt_stat cast to an integer if it fails. Use clnt_perrno() to translate failure statuses into messages.
Warning:
Calling remote procedures with this routine uses
UDP/IP
as the transport; see
clntudp_create()
on
rpc_clnt_create.3n
for restrictions.
You do not have control of timeouts or authentication using
this routine.
enum clnt_stat clnt_broadcast(prognum, versnum, procnum, inproc, in, outproc, out, eachresult) u_long prognum, versnum, procnum; char *in; xdrproc_t inproc; char *out; xdrproc_t outproc; bool_t eachresult;
Like callrpc(), except the call message is broadcast to all locally connected broadcast nets. Each time the caller receives a response, this routine calls eachresult(), whose form is:
int eachresult(out, addr) char *out; struct sockaddr_in *addr;
where
out
is the same as
out
passed to
clnt_broadcast(),
except that the remote procedure's output is decoded there;
addr
points to the address of the machine that sent the results.
If
eachresult()
returns 0
clnt_broadcast()
waits for more replies; otherwise it returns with appropriate
status. If
eachresult()
is
NULL,
clnt_broadcast()
returns without waiting for any replies.
Note: clnt_broadcast() uses AUTH_UNIX style of authentication.
Warning:
Broadcast packets are limited in size to the
maximum transfer unit of the data link.
For Ethernet, the callers argument size should not
exceed 1400 bytes.
enum clnt_stat clnt_call(clnt, procnum, inproc, in, outproc, out, timeout) CLIENT *clnt; u_long procnum; xdrproc_t inproc, outproc; char *in, *out; struct timeval timeout;
Call the remote procedure
procnum
associated with the client handle,
clnt,
which is obtained with an
RPC
client creation routine such as
clnt_create()
(see
rpc_clnt_create.3n
The parameter
in
is the address of the procedure's argument, and
out
is the address of where to place the result;
inproc
is an
XDR
function used to encode the procedure's parameters in
XDR,
and
outproc
is used to decode the procedure's results;
timeout
is the time allowed for a response from the server.
bool_t clnt_freeres(clnt, outproc, out) CLIENT *clnt; xdrproc_t outproc; char *out;
Free any data allocated by the
RPC/XDR
system when it decoded the results of an
RPC
call. The
parameter
out
is the address of the results, and
outproc
is the
XDR
routine describing the results.
This routine returns
TRUE
if the results were successfully
freed,
and
FALSE
otherwise.
Note:
This is equivalent to doing
xdr_free(outproc, out)
(see
xdr_simple.3n
void clnt_geterr(clnt, errp) CLIENT *clnt; struct rpc_err *errp;
Copy the error structure out of the client
handle
to the structure at address
errp.
errp
should point to preallocated space.
void clnt_perrno(stat) enum clnt_stat stat;
Print a message to the standard error corresponding
to the condition indicated by
stat.
A
NEWLINE
is appended at the end of the message.
Used after
callrpc()
or
clnt_broadcast().
void clnt_perror(clnt, str) CLIENT *clnt; char *str;
Print a message to the standard error indicating why an
RPC
call failed;
clnt
is the handle used to do the call.
The message is prepended with string
s
and a colon.
A
NEWLINE
is appended at the end of the message.
Used after
clnt_call().
char *clnt_sperrno(stat) enum clnt_stat stat;
Take the same arguments as clnt_perrno(), but instead of sending a message to the standard error indicating why an RPC failed, return a pointer to a string which contains the message. clnt_sperrno() does not append a NEWLINE at the end of the message.
clnt_sperrno() is used instead of clnt_perrno() if the program does not have a standard error (as a program running as a server quite likely does not), or if the programmer does not want the message to be output with printf.3v or if a message format different than that supported by clnt_perrno() is to be used.
char *clnt_sperror(clnt, str) CLIENT *clnt; char *str;
Like clnt_perror(), except that (like clnt_sperrno()) it returns a string instead of printing to the standard error. Unlike clnt_perror(), it does not append the message with a NEWLINE.
Note: clnt_sperror() returns pointer to a static buffer that is overwritten on each call.
Created by unroff & hp-tools. © somebody (See intro for details). All Rights Reserved. Last modified 11/5/97