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RedHat 9 (Linux i386) - man page for snmp_sess_session (redhat section 3)


       snmp_sess_init,	snmp_sess_open,  snmp_sess_session, snmp_sess_send, snmp_sess_async_send,
       snmp_sess_select_info, snmp_sess_read, snmp_sess_timeout, snmp_sess_close, snmp_sess_error
       - session functions

       #include <net-snmp/session_api.h>

       void snmp_sess_init(struct snmp_session *session);

       void *snmp_sess_open(struct snmp_session *session);

       struct snmp_session *snmp_sess_session(void *handle);

       int snmp_sess_send(void *handle, struct snmp_pdu *pdu);

       int snmp_sess_async_send(void *handle,
				struct snmp_pdu *pdu,
				snmp_callback callback,
				void *callbackData);

       int snmp_sess_select_info(void *handle,
				 int *numfds, fd_set *fdset,
				 struct timeval *timeout,
				 int *block);

       void snmp_sess_read(void *handle, fd_set *fdset);

       void snmp_sess_timeout(void *handle);

       int snmp_sess_close(void *handle);

       void snmp_sess_error(void *handle, int *pcliberr,
			   int *psnmperr, char **pperrstring);

       These functions define a subset of the API that can be used to manage single SNMP sessions
       in a multi-threaded application.  Except for snmp_sess_session(), these functions are sin-
       gle session versions of the traditional SNMP library API.

       Note  that these functions use an opaque pointer (handle in the above prototypes) to iden-
       tify a single session in lieu of a session pointer (as in the traditional API).

       snmp_sess_init() prepares a struct snmp_session that sources transport characteristics and
       common information that will be used for a set of SNMP transactions.  After this structure
       is passed to snmp_sess_open() to create an SNMP session, the structure is no longer  used.
       Instead	the  opaque pointer returned by snmp_sess_open() is used to refer to that session

       SNMP sessions that are created with snmp_sess_open() are not affected by, and  SHOULD  NOT
       BE  USED  WITH,	snmp_select_info(), snmp_read(), snmp_timeout() nor snmp_close().  Rather
       the equivalent single session functions described here should be used.

       snmp_sess_init() and snmp_sess_open() each take as input a pointer to a	struct	snmp_ses-
       sion  object.   This  structure	contains  information for a set of transactions that will
       share similar transport characteristics.  snmp_sess_session()  takes  the  opaque  session
       handle and returns a pointer to its associated struct snmp_session.

       snmp_sess_send()  and  snmp_sess_async_send() each take a pdu parameter, which points to a
       struct snmp_pdu object containing information that describes a transaction  that  will  be
       performed over an open session.

       Consult snmp_api.h for the definitions of these structures.

       snmp_sess_select_info(), snmp_sess_read() and snmp_sess_timeout() provide an interface for
       the use of the select(2) system call so that SNMP transactions for a  single  session  can
       occur asynchronously.

       snmp_sess_select_info() is passed the information that would have been passed to select(2)
       in the absence of SNMP.	For example, this might include file descriptors associated  with
       the  main  loop of a graphical application. This information is modified so that SNMP will
       get the service it requires from the call to select(2).	In this case, numfds,  fdset  and
       timeout	correspond  to the nfds, readfds and timeout arguments to select(2) respectively.
       The only exception is that timeout must ALWAYS point to an allocated (but  perhaps  unini-
       tialized) struct timeval (it cannot be NULL as for select(2)).  If timeout would have been
       passed as NULL, block is instead set to true, and timeout is treated as	undefined.   This
       same rule applies upon return from snmp_select_info().

       After calling snmp_sess_select_info() , select(2) should be called with the returned data.
       When it returns, snmp_sess_read() should then be called	with  the  fd_set  returned  from
       select(2).   This will read any input from this session's SNMP socket.  If select(2) times
       out (that is, it returns zero), snmp_sess_timeout() should be called to see if  a  timeout
       has occurred on the SNMP session.

       Error return status from snmp_sess_open() is indicated by return of a NULL pointer.  Error
       return status from snmp_sess_close() and snmp_sess_send() is indicated by a  return  value
       of 0.  A successful status will return 1.

       Further	information  can be obtained by using snmp_sess_error() to see what type of error
       has occurred.  This function returns the SNMP snmp_errno variable, the value of the system
       errno  variable,  and a string interpretation of both variables.  The string must be freed
       after use by the caller.

       For errors returned by  snmp_sess_open(),  use  the  corresponding  function  snmp_error()
       instead of snmp_sess_error().

       Consult	snmp_api.h  for  the complete set of SNMP library error values.  The SNMP library
       error value snmperr can be one of the following values:

	 SNMPERR_GENERR 	  A generic error occurred.

	 SNMPERR_BAD_LOCPORT	  The local port was bad because it had already been allocated or
				  permission was denied.

	 SNMPERR_BAD_ADDRESS	  The host name or address given was not useable.

	 SNMPERR_BAD_SESSION	  The specified session was not open.

















       select(2), snmp_api(3), snmp_api.h

4.2 Berkeley Distribution		   07 Mar 2002				 SNMP_SESS_API(3)

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