RPC_CLNT_CREATE(3)

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

LIBRARY
libc

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_vers(const char * host, const rpcprog_t prognum, rpcvers_t *vers_outp, const rpcvers_t vers_low, const rpcvers_t vers_high, char *nettype);
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);
char *
clnt_spcreateerror(const char *s);
CLIENT *
clnt_raw_create(const rpcprog_t prognum, const rpcvers_t versnum);
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_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);

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.

ROUTINES

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

    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_SVC_ADDR | struct netbuf * | get servers address
    CLGET_FD | int * | get fd from handle
    CLSET_FD_CLOSE | void | close fd on destroy
    CLSET_FD_NCLOSE | void | don't close fd on destroy
    CLGET_VERS | unsigned long * | get RPC program version
    CLSET_VERS | unsigned long * | set RPC program version
    CLGET_XID | unsigned long * | get XID of previous call
    CLSET_XID | unsigned long * | set XID of next 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.

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 environment 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(8) service. This mismatch will be discovered by a clnt_call() later (see rpc_clnt_calls(3)).

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(8) service. This mismatch will be discovered by a clnt_call() later (see rpc_clnt_calls(3)). 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.

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(3)).

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(3)). 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.

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.

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.

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's address space, so the corresponding RPC server should live in the same address space; (see svc_raw_create() in rpc_svc_create(3)). 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().

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(8)) is not consulted for the address of the remote service.

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.

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.

SEE ALSO
rpc(3), rpc_clnt_auth(3), rpc_clnt_calls(3), rpcbind(8)