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SNMP_API(3)                                       Net-SNMP                                       SNMP_API(3)



NAME
       snmp_sess_init,  snmp_open,  snmp_send,  snmp_free_pdu,  snmp_select_info,  snmp_read,  snmp_timeout,
       snmp_close, snmp_perror, snmp_sess_perror, snmp_error, snmp_api_errstring -  send  and  receive  SNMP
       messages

SYNOPSIS
       #include <net-snmp/session_api.h>

       void snmp_sess_init ( struct snmp_session * );

       struct snmp_session * snmp_open ( struct snmp_session *);
              /* Input parameter not used in active sessions */

       int snmp_send ( struct snmp_session *session,
              struct snmp_pdu *pdu );

       int snmp_select_info ( int *numfds, fd_set *fdset,
              struct timeval *timeout, int *block );

       void snmp_read ( fd_set *fdset );

       void snmp_timeout ( void );

       int snmp_close ( struct snmp_session *session );

       void snmp_free_pdu ( struct snmp_pdu *pdu );

       void snmp_error ( struct snmp_session *session,
              int *pcliberr, int *psnmperr, char **pperrstring );

       char *snmp_api_errstring ( int snmperr );

       void snmp_perror ( char * msg );
              /* for parsing errors only */

       void snmp_sess_perror (char * msg, struct snmp_session *);
              /* all other SNMP library errors */


DESCRIPTION
       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_open to create an SNMP session, the structure is not used.

       Snmp_open  returns a pointer to a newly-formed struct snmp_session object, which the application must
       use to reference the active SNMP session.

       Snmp_send and snmp_free_pdu each take as input a pointer to a struct snmp_pdu object.  This structure
       contains information that describes a transaction that will be performed over an open session.

       Consult snmp_api.h for the definitions of these structures.

       Snmp_read,  snmp_select_info, and snmp_timeout provide an interface for the use of the select(2) sys-tem system
       tem call so that SNMP transactions can occur asynchronously.

       Snmp_select_info is given the information that would have been passed to select  in  the  absence  of
       SNMP.   For  example,  this might include window update information.  This information is modified so
       that SNMP will get the service it requires from the call to select.  In this case, numfds, fdset, and
       timeout  correspond  to  the  nfds, readfds, and timeout arguments to select, respectively.  The only
       exception is that timeout must always point  to  an  allocated  (but  perhaps  uninitialized)  struct
       timeval.   If timeout would have been passed as NULL, block is set to true, and timeout is treated as
       undefined.  This same rule applies upon return from snmp_select_info.

       After calling snmp_select_info, select is called  with  the  returned  data.   When  select  returns,
       snmp_read  should  be  called  with the fd_set returned from select to read each SNMP socket that has
       input.  If select times out, snmp_timeout should be called to see if the  timeout  was  intended  for
       SNMP.

DIAGNOSTICS
       Previous versions of the library used snmp_get_errno to read the global variable snmp_errno which may
       have held the error status within the SNMP library.  The existing method snmp_perror should  be  used
       to log ASN.1 coding errors only.

       The  new  method snmp_sess_perror is provided to capture errors that occur during the processing of a
       particular SNMP session.  Snmp_sess_perror calls snmp_error function to obtain the "C" library  error
       errno  , the SNMP library error snmperr , and the SNMP library detailed error message that is associ-ated associated
       ated with an error that occurred during a given session.

       Note that in all cases except one, snmp_sess_perror  should  be  handed  the  struct  snmp_session  *
       pointer  returned  from  snmp_open.   If  snmp_open  returns  a  null  pointer, pass the INPUT struct
       snmp_session * pointer used to call snmp_open.

       Error return status from snmp_close and snmp_send is indicated by return of 0.  A  successful  status
       will  return  a  1  for  snmp_close  and the request id of the packet for snmp_send.  Upon successful
       return from snmp_send the pdu will be freed by the library.

       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.

         SNMPERR_TOO_LONG

         SNMPERR_NO_SOCKET

         SNMPERR_V2_IN_V1

         SNMPERR_V1_IN_V2

         SNMPERR_BAD_REPEATERS

         SNMPERR_BAD_REPETITIONS

         SNMPERR_BAD_ASN1_BUILD

         SNMPERR_BAD_SENDTO

         SNMPERR_BAD_PARSE

         SNMPERR_BAD_VERSION

         SNMPERR_NOAUTH_DESPRIV

         SNMPERR_ABORT

         SNMPERR_UNKNOWN_PDU

         SNMPERR_TIMEOUT

       A string representation of the error code can be obtained with  snmp_api_errstring,  and  a  standard
       error message may be printed using snmp_perror that functions like the perror standard routine.

SEE ALSO
       select(2), snmp_api.h



4.2 Berkeley Distribution                        21 Oct 1999                                     SNMP_API(3)