snmp_agent_api - embedding an agent into a external appli­
       cation


SYNOPSIS

       #include <ucd-snmp/ucd-snmp-config.h>
       #include <ucd-snmp/ucd-snmp-includes.h>
       #include <ucd-snmp/ucd-snmp-agent-includes.h>

       main () {
         int agentx_subagent=1; /* change this if you're a master agent */

         snmp_enable_stderrlog();

         /* if we're an agentx subagent */
         if (agentx_subagent) {
             /* make us a agentx client. */
             ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_ROLE, 1);
         }

         init_agent("yourappname");

         /* initialize your mib code here */
         init_my_mib_code();

         /* yourappname will be used to read yourappname.conf files. */
         init_snmp("yourappname");

         /* If we're going to be a snmp master agent */
         if (!agentx_subagent)
             init_master_agent(161, NULL, NULL);  /* open port 161 (UDP:snmp) */

         /* you're main loop here... */
         while(whatever) {
             /* if you use select(), see snmp_api(3) */
             /*     --- OR ---  */
             agent_check_and_process(0); /* 0 == don't block */
         }

         /* at shutdown time */
         snmp_shutdown("yourappname");
       }

       Then:
       cc ... -lucdagent -lucdmibs -lsnmp # other libraries may be needed here


DESCRIPTION

       Our goal is to create a easy to use interface to the  ucd-
       snmp  package  such  that  you can take code that you have
       written that has been designed to be a ucd-snmp mib module
       and  embed  it  into an external application where you can
       either chose to be a SNMP master agent or an  AgentX  sub-
       agent  using  the same mib module code.  Our suggestion is

       master  agent and chose to become an AgentX subagent which
       then attaches to the master.

       Starting with version 4.1, the ucd-snmp package provides a
       pair  of  libraries that enables easy embedding of an SNMP
       or AgentX agent into an external software package.  AgentX
       is  an extensible protocol designed to allow multiple SNMP
       sub-agents all run on one machine under a single SNMP mas­
       ter agent.  It is defined in RFC 2741.

       You  will  need  to perform a few tasks in order to accom­
       plish this. First off, you will need  to  initialize  both
       the  SNMP library and the SNMP agent library. As indicated
       above, this is  done  slightly  differently  depending  on
       whether  or not you are going to perform as a master agent
       or an AgentX sub-agent.


CONFIGURATION

       If you intend to operate as an AgentX sub-agent, you  will
       have to configured the ucd-snmp package as follows:
                ./configure --with-mib-modules="agentx/subagent"
       Additionally, you will need to link against the libucdmibs
       library and call subagent_pre_init() as indicated above.


COMPILING

       In order to make use of any of the  above  API,  you  will
       need  to  clinch  against  at  least  two  libraries:  the
       libucdagent library and the libsnmp library. Additionally,
       if  you plan to make use of any of the code in the agent's
       mib modules (like the AgentX subagent support),  you  will
       need to link against the libucdmibs library as well.


FUNCTIONS

       snmp_enable_stderrlog()
              Logs  error output from the SNMP agent to the stan­
              dard error stream.

       ds_set_boolean()
              Please see the  default_store(3)  manual  page  for
              more information about this API.

       init_agent(char *name)
              Initializes  the  embedded  agent.   This should be
              called before the init_snmp() call.  name  is  used
              to dictate what .conf file to read when init_snmp()
              is called later.

       init_snmp(char *name)
              Initializes the SNMP library.  Note that one of the
              things  this  will do will be to read configuration
              files in an effort to configure  your  application.
              It  will  attempt  to  read the configuration files
              named by the name string that you  passed  in.   It

              instance.     Please   see   the    read_config(3),
              snmp_config(5),  and snmpd.conf(5) manual pages for
              further details on this subject.

       init_master_agent(port, NULL, NULL)
              Initializes the master agent and opens all its nec­
              essary  ports.  port is the port you want to listen
              for SNMP requests on.

       agent_check_and_process(int block)
              This checks for packets arriving on the  SNMP  port
              and  processes them if some are found.  If block is
              non-zero, the function  call  will  block  until  a
              packet  arrives  or  an  alarm  must  be  run  (see
              snmp_alarm(3)). The return value from this function
              is  a  positive  integer if packets were processed,
              zero if an  alarm  occurred  and  -1  if  an  error
              occured.

       snmp_shutdown(char *name);
              This  shuts  down the agent, saving any needed per­
              sistent storage, etc.


SEE ALSO

       select(2), snmp_api(3),  default_store(3),  snmp_alarm(3),
       read_config(3), snmp_config(5), snmpd.conf(5)


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