rpc_clnt_create(3N)

NAME

rpc_clnt_create: clnt_control(), clnt_create(), clnt_create_timed(), clnt_create_vers(), clnt_create_vers_timed(), 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

SYNOPSIS

#include <rpc/rpc.h>

bool_t clnt_control(CLIENT *clnt,
const u_int req,
char *info);

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

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

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

CLIENT *clnt_create_vers_timed(const char *host,
const rpcprog_t prognum,
rpcvers_t *vers_outp,
const rpcvers_t vers_low,
const rpcvers_t vers_high,
char *nettype,
const struct timeval *timeout);

void clnt_destroy(CLIENT *clnt);

CLIENT *clnt_dg_create(const int fildes,
const struct netbuf *svcaddr,
const rpcprog_t prognum,
const rpcvers_t versnum,
const u_int sendsz,
const u_int recvsz);

void clnt_pcreateerror(const char *s);

CLIENT *clnt_raw_create(const rpcprog_t prognum,
const rpcvers_t versnum);

char *clnt_spcreateerror(const char *s);

CLIENT *clnt_tli_create(const int fildes,
const struct netconfig *netconf,
const struct netbuf *svcaddr,
const rpcprog_t prognum,
const rpcvers_t versnum,
const u_int sendsz,
const u_int recvsz);

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

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

CLIENT *clnt_vc_create(const int fildes,
const struct netbuf *svcaddr,
const rpcprog_t prognum,
const rpcvers_t versnum,
const u_int sendsz,
const u_int recvsz);

struct rpc_createerr rpc_createerr; 

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 thread-safe. In the case of multithreaded applications, the _REENTRANT flag must be defined on the command line at compilation time (-D_REENTRANT). When the _REENTRANT flag is defined, rpc_createerr becomes a macro which enables each thread to have its own rpc_createerr.

The HP-UX implementation of RPC only supports the X/Open Transport Interface (XTI). Applications that are written using the Transport Layer Interface (TLI) and wish to use RPC, must convert their application to XTI.

Routines

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

bool_t clnt_control();

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

If the timeout is set using clnt_control(), the timeout argument passed by clnt_call() is ignored in all subsequent calls.

If the timeout value is set to 0, clnt_control() immediately returns RPC_TIMEDOUT. Set the timeout parameter to 0 for batching calls.

CLGET_SERVER_ADDR struct netbuf *  get server's address
CLGET_SVC_ADDR    struct netbuf *  get server's address
CLGET_FD          int *            get the associated file descriptor
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        rpcvers_t        get the RPC program's version
                                   number associated with the
                                   client handle
CLSET_VERS        rpcvers_t        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
CLGET_PROG        rpcprog_t        get program number
CLSET_PROG        rpcprog_t        set program number

The following operations are valid for connection-oriented transports only:

CLSET_IO_MODE          rpciomode_t *     set the IO mode used
                                         to send one-way requests.

The argument for this operation can be either:

RPC_CL_BLOCKING: All sending operations block until the underlying transport protocol has accepted requests. If you specify this argument you cannot use flush and getting and setting buffer size is meaningless.
RPC_CL_NONBLOCKING: Sending operations do not block and return as soon as requests enter the buffer. You can now use non-blocking I/O. The requests in the buffer are pending. The requests are sent to the server as soon as a two-way request is sent or a flush is done. You are responsible for flushing the buffer. When you choose the RPC_CL_NONBLOCKING argument you have a choice of flush modes as specified by CLSET_FLUSH_MODE.

CLGET_IO_MODE          rpciomode_t *     get the current IO mode
CLSET_FLUSH_MODE       rpcflushmode_t *  set the flush mode

The flush mode can only be used in non-blocking I/O mode. The argument for this operation can be either:

RPC_CL_BESTEFFORT_FLUSH: All flushes send requests in the buffer until the transport end-point blocks. If the transport connection is congested, the call returns directly.
RPC_CL_BLOCKING_FLUSH: Flush blocks until the underlying transport protocol accepts all pending requests into the queue.

CLGET_FLUSH_MODE       rpcflushmode_t *  get the current flush mode
CLFLUSH                rpcflushmode_t    flush the pending requests

This command can only be used in non-blocking I/O mode. The flush policy depends on which of the following parameters is specified:

RPC_CL_DEFAULT_FLUSH or NULL: The flush is done according to the current flush mode policy (see the CLSET_FLUSH_MODE option).
RPC_CL_BESTEFFORT_FLUSH: The flush tries to send pending requests without blocking; the call returns directly. If the transport connection is congested, this call could return without the request being sent.
RPC_CL_BLOCKING_FLUSH: The flush sends all pending requests. This call will block until all the requests have been accepted by the transport layer.

CLSET_CONNMAXREC_SIZE  int *             set the buffer size
CLGET_CONNMAXREC_SIZE  int *             get the current size of the
                                         buffer
CLGET_CURRENT_REC_SIZE int *             get the size of the pending
                                         requests stored in the
                                         buffer. Use of this command
                                         is only recommended when you
                                         are in non-blocking I/O
                                         mode. The current size of
                                         the buffer is always zero
                                         when the handle is in
                                         blocking mode as the buffer
                                         is not used in this mode.

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()

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 that 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()

Generic client creation routine which is similar to clnt_create() but with the additional parameter timeout, which 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()

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.

CLIENT *clnt_create_vers_timed()

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

void clnt_destroy()

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()

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 timeout and the total timeout 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()

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()

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' 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()

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 multithreaded applications, this buffer is implemented as thread-specific data.

CLIENT *clnt_tli_create()

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()

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()

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()

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.

MULTITHREAD USAGE

Thread Safe:: Yes
Cancel Safe:: Yes
Fork Safe:: No
Async-cancel Safe:: No
Async-signal Safe:: No

These functions can be called safely in a multithreaded environment. They may be cancellation points in that they call functions that are cancel points.

In a multithreaded environment, these functions are not safe to be called by a child process after fork() and before exec(). These functions should not be called by a multithreaded application that supports asynchronous cancellation or asynchronous signals.

rpc_clnt_create(3N)

Technical documentation

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NAME

SYNOPSIS

DESCRIPTION

Routines

MULTITHREAD USAGE

SEE ALSO