NAME

       snmp_sess_init,   snmp_open,   snmp_send,  snmp_async_send,  snmp_select_info,  snmp_read,  snmp_timeout,
       snmp_synch_response,  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_async_send ( netsnmp_session *session,
                                       netsnmp_pdu *pdu,
                                       snmp_callback callback,
                                       void *callbackData);

       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_synch_response ( netsnmp_session *session,
              netsnmp_pdu *pdu,
              netsnmp_pdu **response);

       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 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 netsnmp_session object, which the application must use to
       reference the active SNMP session.

       snmp_send and snmp_async_send() each take 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.

       With  the  snmp_async_send()  call,  snmp_read  will  invoke  the specified callback when the response is
       received.

       Snmp_read, snmp_select_info, and snmp_timeout provide an interface for the use of  the  select(2)  system
       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.

       snmp_synch_response  is  a  convenience  routine  that  will  send the request, wait for the response and
       process it before returning.  See the descriptions of snmp_send ,  snmp_read etc for details.

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  associated
       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),   netsnmp_sess_api(3),   netsnmp_mib_api(3),    netsnmp_pdu_api(3),    netsnmp_varbind_api(3),
       snmp_api.h