[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    rpc_clnt_create(3N) manual page Table of Contents

Name

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

MT-Level

MT-S afe

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 request to the server. On receipt of the request, the server calls a dispatch routine to perform the requested service, and then sends a reply.

These routines are MT-S afe. In the case of multithreaded applications, the _REENTRANT flag must be defined on the command line at compilation time
( When the _REENTRANT flag is defined, rpc_createerr becomes a macro which enables each thread to have its own rpc_createerr.

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 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 timeval *    set total timeout
CLGET_TIMEOUT    struct timeval *    get total timeout
Note: if you set the timeout using
clnt_control(), the timeout argument passed by clnt_call() is ignored in all subsequent calls.
Note: If you set the timeout value to
0 clnt_control() immediately returns an error (RPC_TIMEDOUT ). Set the timeout parameter to 0 for batching calls. 


CLGET_FD    int *    get the associated file descriptor
CLGET_SVC_ADDR    struct netbuf *    get servers address
CLSET_FD_CLOSE    void    close the file descriptor when
        destroying the client handle
        (see clnt_destroy())
CLSET_FD_NCLOSE    void    do not close the file
        descriptor when destroying
        the client handle



CLGET_VERS    unsigned long *    get the RPC program’s version
        number associated with the
        client handle

CLSET_VERS    unsigned long *    set the RPC program’s version
        number associated with the
        client handle.  This assumes
        that the RPC server for this
        new version is still listening
        at the address of the previous
        version.
CLGET_XID    unsigned long *    get the XID of the previous
        remote procedure call
CLSET_XID    unsigned long *    set the XID of the next
        remote procedure call
The following operations are valid for
connectionless transports only: 


CLSET_RETRY_TIMEOUT   struct timeval *    set the retry timeout
CLGET_RETRY_TIMEOUT  struct timeval *    get the retry timeout
The retry timeout is the time that
RPC waits for the server to reply before retransmitting the request.
clnt_control()
returns TRUE on success and FALSE 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 bottom order in the netconfig database.
clnt_create()
tries all the transports of the nettype class available from the NETPATH environment variable and the netconfig database, and chooses the first successful one. A default timeout is set and can be modified using clnt_control(). This routine returns NULL if it fails. The clnt_pcreateerror() routine can be used to print the reason for failure.
Note:
clnt_create() returns a valid client handle even if the particular version number supplied to clnt_create() is not registered with the rpcbind service. This mismatch will be discovered by a clnt_call later (see rpc_clnt_calls(3N) ).

CLIENT *clnt_create_timed(const char *host, const u_long prognum, const u_long versnum, const char *nettype, const struct timeval *timeout);

Generic client creation routine which is similar to
clnt_create() but which also has the additional parameter timeout that specifies the maximum amount of time allowed for each transport class tried. In all other respects, the clnt_create_timed() call behaves exactly like the clnt_create() call.

CLIENT *clnt_create_vers(const char *host, const u_long prognum, u_long *vers_outp, const u_long vers_low, const u_long vers_high, char *nettype);

Generic client creation routine which is similar to
clnt_create() but which also checks for the version availability. host identifies the name of the remote host where the server is located. nettype indicates the class transport protocols to be used. If the routine is successful it returns a client handle created for the highest version between vers_low and vers_high that is supported by the server. vers_outp is set to this value. That is, after a successful return vers_low <= *vers_outp <= vers_high. If no version between vers_low and vers_high is supported by the server then the routine fails and returns NULL . A default timeout is set and can be modified using clnt_control(). This routine returns NULL if it fails. The clnt_pcreateerror() routine can be used to print the reason for failure.
Note:
clnt_create() returns a valid client handle even if the particular version number supplied to clnt_create() is not registered with the rpcbind service. This mismatch will be discovered by a clnt_call later (see rpc_clnt_calls(3N) ). However, clnt_create_vers() does this for you and returns a valid handle only if a version within the range supplied is supported by the server.

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(), the file descriptor will be closed.
The caller should call
auth_destroy(clnt->cl_auth) (before calling clnt_destroy()) to destroy the associated AUTH structure (see rpc_clnt_auth(3N) ).

CLIENT *clnt_dg_create(const int fildes, 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 fildes 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) ). 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. This routine returns NULL if it fails.

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 an
RPC client handle 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_svc_create(3N) ). This allows simulation of RPC and measurement of RPC overheads, such as round trip times, without any kernel or networking interference. 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 a buffer that is overwritten on each call. In multithread applications, this buffer is implemented as thread-specific data.

CLIENT *clnt_tli_create(const int fildes, const struct netconfig *netconf, const struct netbuf *svcaddr, 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. fildes 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 fildes is RPC_ANYFD and netconf is NULL , a RPC_UNKNOWNPROTO error is set. If fildes 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_pcreateerror() routine can be used to print the reason for failure. The remote rpcbind service (see rpcbind(1M) ) is not 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);

Like
clnt_create() except clnt_tp_create() tries only one transport specified through netconf.
clnt_tp_create()
creates a client handle for the program prognum, the version versnum, and for the transport 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_pcreateerror() routine can be used to print the reason for failure.

CLIENT *clnt_tp_create_timed(const char *host, const u_long prognum, const u_long versnum, const struct netconfig *netconf, const struct timeval *timeout);

Like
clnt_tp_create() except clnt_tp_create_timed() has the extra parameter timeout which specifies the maximum time allowed for the creation attempt to succeed. In all other respects, the clnt_tp_create_timed() call behaves exactly like the clnt_tp_create() call.

CLIENT *clnt_vc_create(const int fildes, 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 fildes 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() does not consult the remote rpcbind service for this information. 


struct rpc_createerr rpc_createerr;
A global variable whose value is set by any
RPC client handle creation routine that fails. It is used by the routine clnt_pcreateerror() to print the reason for the failure.
In multithreaded applications,
rpc_createerr becomes a macro which enables each thread to have its own rpc_createerr.

See Also

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

Table of Contents