Provided by: libsnmp-dev_5.9.4+dfsg-1.1ubuntu7_amd64 
NAME
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_synch_response, snmp_sess_close,
snmp_sess_error - session functions
SYNOPSIS
#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_synch_response ( void *handle,
netsnmp_pdu *pdu,
netsnmp_pdu **response);
int snmp_sess_close(void *handle);
void snmp_sess_error(void *handle, int *pcliberr,
int *psnmperr, char **pperrstring);
DESCRIPTION
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 henceforth.
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.
With the snmp_sess_async_send() call, snmp_sess_read will invoke the specified callback when the response
is received.
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.
snmp_sess_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_sess_send , snmp_sess_read etc for details.
DIAGNOSTICS
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.
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_RCVFROM
SNMPERR_BAD_PARSE
SNMPERR_BAD_VERSION
SNMPERR_BAD_COMMUNITY
SNMPERR_NOAUTH_DESPRIV
SNMPERR_ABORT
SNMPERR_UNKNOWN_PDU
SNMPERR_TIMEOUT
SEE ALSO
select(2), netsnmp_session_api(3), netsnmp_pdu_api(3), netsnmp_varbind_api(3), netsnmp_mib_api(3),
snmp_api.h
V5.9.4.pre2 19 May 2011 NETSNMP_SESS_API(3)