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NETSNMP_SESSION_API(3)                            Net-SNMP                            NETSNMP_SESSION_API(3)



NAME
       snmp_sess_init,   snmp_open,   snmp_send,   snmp_select_info,  snmp_read,  snmp_timeout,  snmp_close,
       snmp_perror, snmp_sess_perror, snmp_error, snmp_api_errstring - netsnmp_session_api functions

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

       void snmp_sess_init ( netsnmp_session*sess);

       netsnmp_session* snmp_open ( netsnmp_session *sess);
              /* Input parameter not used in active sessions */

       int snmp_send ( netsnmp_session *session,
              netsnmp_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 ( netsnmp_session *session);
       int snmp_close_sessions ( void );


   Error Reporting
       (Move to output_api(3))
       void snmp_error ( netsnmp_session *session,
              int *pcliberr,int *psnmperr,char **pperrstring);

       char *snmp_api_errstring ( intsnmperr);

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

       void snmp_sess_perror (char *msg,netsnmp_session *sess);
              /* all other SNMP library errors */


DESCRIPTION
       Snmp_sess_init prepares a netsnmp_session that sources transport characteristics and common  informa-tion information
       tion  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 netsnmp_session object, which the application must  use
       to reference the active SNMP session.

       Snmp_send takes as input a pointer to a netsnmp_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 netsnmp_session * pointer
       returned from snmp_open.  If snmp_open returns a null  pointer,  pass  the  INPUT  netsnmp_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



V5.6                                             13 Aug 2010                          NETSNMP_SESSION_API(3)