NAME

rpc_clnt_create: clnt_control, clnt_create, clnt_destroy, clnt_dg_create, clnt_pcreateerror, clnt_raw_create, clnt_spcreateerror, clnt_tli_create, clnt_tp_create, clnt_vc_create - library routines for dealing with creation and manipulation of CLIENT handles

DESCRIPTION

RPC library routines allow C language programs to make procedure calls on other machines across the network. First a CLIENT handle is created and then the client calls a procedure to send a data packet to the server. Upon receipt of the packet, the server calls a dispatch routine to perform the requested service, and then sends back a reply.

Routines

See rpc(3N) for the definition of the CLIENT data structure.

#include <rpc/rpc.h>
bool_t
clnt_control(CLIENT *clnt, const u_int req, char *info);

A function macro used to change or retrieve various information about a client object. req indicates the type of operation, and info is a pointer to the information. For both connectionless and connection-oriented transports, the supported values of req and their argument types and what they do are:

CLSET_TIMEOUT struct timevalset total timeout CLGET_TIMEOUT struct timevalget total timeout

Note: if you set the timeout using clnt_control, the timeout parameter passed to clnt_call will be ignored in all future calls.

CLGET_FD    int         get the associated file descriptor
CLGET_SVC_ADDR          struct netbufget servers address
CLSET_FD_CLOSE          intclose the file descriptor when
                        destroying the client handle
                        [see clnt_destroy]
CLSET_FD_NCLOSE         intdo not close the file
                        descriptor when destroying
                        the client handle

The following operations are valid for connectionless transports only:

CLSET_RETRY_TIMEOUT      struct timevalset the retry timeout

CLGET_RETRY_TIMEOUT      struct timevalget the retry timeout

The retry timeout is the time that RPC waits for the server to reply before retransmitting the request.

clnt_control returns 1 on success and 0 on failure.

CLIENT *
clnt_create(const char *host, const u_long prognum,
     const u_long versnum, const char *nettype);

Generic client creation routine for program prognum and version versnum. host identifies the name of the remote host where the server is located. nettype indicates the class of transport protocol to use. The transports are tried in left to right order in NETPATH variable or in top to down order in the netconfig database.

clnt_create tries all the  transports  of  the  nettype
class  available  from the NETPATH environment variable
and the the netconfig database, and chooses  the  first
successful  one.   Default timeouts are set, but can be
modified using clnt_control.
void
clnt_destroy(CLIENT *clnt);

A function macro that destroys the client's RPC handle. Destruction usually involves deallocation of private data structures, including clnt itself. Use of clnt is undefined after calling clnt_destroy. If the RPC library opened the associated file descriptor, or CLSET_FD_CLOSE was set using clnt_control, it will be closed.

CLIENT *
clnt_dg_create(const int fd, const struct netbuf *svcaddr,
     const u_long prognum, const u_long versnum,
     const u_int sendsz, const u_int recvsz);

This routine creates an RPC client for the remote program prognum and version versnum; the client uses a connectionless transport. The remote program is located at address svcaddr. The parameter fd is an open and bound file descriptor. This routine will resend the call message in intervals of 15 seconds until a response is received or until the call times out. The total time for the call to time out is specified by clnt_call [see clnt_call in rpc_clnt_calls(3N)]. This routine returns NULL if it fails. The retry time out and the total time out periods can be changed using clnt_control. The user may set the size of the send and receive buffers with the parameters sendsz and recvsz; values of 0 choose suitable defaults.

void
clnt_pcreateerror(const char *s);

Print a message to  standard  error  indicating  why  a
client RPC handle could not be created.  The message is
prepended with the string s and a colon,  and  appended
with a newline.
CLIENT *
clnt_raw_create(const u_long prognum, const u_long versnum);

This routine creates a toy RPC client  for  the  remote
program  prognum  and  version  versnum.  The transport
used to pass messages to the service is a buffer within
the  process's  address space, so the corresponding RPC
server should live in  the  same  address  space;  [see
svc_raw_create  in  rpc_clnt_calls(3N)].   This  allows
simulation of RPC and  acquisition  of  RPC  overheads,
such  as round trip times, without any kernel interfer-
ence.   This  routine  returns  NULL   if   it   fails.
clnt_raw_create should be called after svc_raw_create.
char *
clnt_spcreateerror(const char *s);

Like clnt_pcreateerror, except that it returns a string instead of printing to the standard error. A newline is not appended to the message in this case.

Warning:  returns a pointer  to  static  data  that  is
overwritten on each call.
CLIENT *
clnt_tli_create(const int fd, const struct netconfig *netconf,
     const struct netbuf *svcaddr, u const_long prognum,
     const u_long versnum, const u_int sendsz,
     const u_int recvsz);

This routine creates an RPC client handle for the remote program prognum and version versnum. The remote program is located at address svcaddr. If svcaddr is NULL and it is connection-oriented, it is assumed that the file descriptor is connected. For connectionless transports, if svcaddr is NULL, RPC_UNKNOWNADDR error is set. fd is a file descriptor which may be open, bound and connected. If it is RPC_ANYFD, it opens a file descriptor on the transport specified by netconf. If netconf is NULL, a RPC_UNKNOWNPROTO error is set. If fd is unbound, then it will attempt to bind the descriptor. The user may specify the size of the buffers with the parameters sendsz and recvsz; values of 0 choose suitable defaults. Depending upon the type of the transport (connection-oriented or connectionless), clnt_tli_create calls appropriate client creation routines. This routine returns NULL if it fails. The clnt_pcreaterror routine can be used to print the reason for failure. The remote rpcbind service [see rpcbind(1M)] will not be consulted for the address of the remote service.

CLIENT *
clnt_tp_create(const char *host, const u_long prognum,
     const u_long versnum, const struct netconfig *netconf);

clnt_tp_create creates a client handle  for  the  tran-
sport  specified  by netconf.  Default options are set,
which can be changed  using  clnt_control  calls.   The
remote  rpcbind  service  on the host host is consulted
for the address of the remote  service.   This  routine
returns NULL if it fails.  The clnt_pcreaterror routine
can be used to print the reason for failure.
CLIENT *
clnt_vc_create(const int fd, const struct netbuf *svcaddr,
     const u_long prognum, const u_long versnum,
     const u_int sendsz, const u_int recvsz);

This routine creates an RPC client for the remote program prognum and version versnum; the client uses a connection-oriented transport. The remote program is located at address svcaddr. The parameter fd is an open and bound file descriptor. The user may specify the size of the send and receive buffers with the parameters sendsz and recvsz; values of 0 choose suitable defaults. This routine returns NULL if it fails.

The address svcaddr should not be NULL and should point to the actual address of the remote program. clnt_vc_create will not consult the remote rpcbind service for this information.

SEE ALSO

rpcbind(1M), rpc(3N), rpc_clnt_auth(3N), rpc_clnt_calls(3N).