Provided by: libsnmp-dev_5.4.3~dfsg-2.4ubuntu1_amd64 bug


       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);

       int 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
       single session versions of the traditional SNMP library API.

       Note  that  these  functions  use  an  opaque  pointer (handle in the above prototypes) to
       identify 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_session  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
       uninitialized) 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