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