Previously working os-apcupsd plugin has stopped working.

[mrzaz]

Hello,
I have a APC UPS SMT750IC but uses "APC PowerShute Serial Shutdown" in my server
to handle shutdown of the server (as my old standalone SNMP card was to old for the new UPS)
but also act as a NIS for other devices like Synology DS920+ and OpnSense via the "os-apcupsd"
plugin and it has been working fine for a couple of years.
Both from Synology but also from OpnSense.

I have relied on that it was working good for a very long time so i forgot to check it in more
details in OpnSense but tonight I realised that it was broken.  No info in the dashboard widget,
no info in the apcupsd plugin status screen. Found one problem that was related to NIS port 3551
being used but changed to 3552 to test but still not resolved.

I use "Ether, snmp, 192.168.x.x:161:APC:private" as config which has been working for years but now stopped working.

Log shows
2026-05-24T03:11:37 Notice apcupsd apcupsd 3.14.14 (31 May 2016) freebsd startup succeeded

I have traced the port 161 signalling out of OpnSense on LAN going out OK.
I then traced the port 161 signalling in to server with "PowerShute Serial Shutdown" application and it is comming in.
But still nothing.

I then checked Synology UPS settings and it is working fine, both on SNMP v2c (using private) and also v3 with username/psw.

I tried to start it manually to get startup log entries but nothing found really apart from
Selected community: "private"
Selected MIB: "APC"
But there are NO successful SNMP reads afterward.

Have no clue why this started happening, especially as it works totally fine from Synology NAS and also from OpnSense for a long time.

Does anyone else use "os-apsupsd" plugin that also experience the same issue ?

I am running on latest version of OpnSense/Apsupsd.

BR,
Dan Lundqvist
Stockholm, Sweden

[viragomann]

I have traced the port 161 signalling out of OpnSense on LAN going out OK.
I then traced the port 161 signalling in to server with "PowerShute Serial Shutdown" application and it is comming in.
But still nothing.

So OPNsense doesn't get a response from the server?
If so you should rather look for the reason on the server.

Was the OPNsense interface address changed by any chance?
In this case you might have to update the access control list of the SNMP server.

[mrzaz]

I have traced the port 161 signalling out of OpnSense on LAN going out OK.
I then traced the port 161 signalling in to server with "PowerShute Serial Shutdown" application and it is comming in.
But still nothing.

So OPNsense doesn't get a response from the server?
If so you should rather look for the reason on the server.

Was the OPNsense interface address changed by any chance?
In this case you might have to update the access control list of the SNMP server.

I have enabled some debugging in the PowerShute and I could see the following:

OpnSense
2026-05-24 18:13:23,492 [DefaultUDPTransportMapping_0.0.0.0/161] DEBUG - [Util.ExtendedCommandProcessor.()] got Request from:[B@3611beffCommandResponderEvent[securityModel=1, securityLevel=1, maxSizeResponsePDU=2147483647, pduHandle=PduHandle[476310], stateReference=StateReference[msgID=0,pduHandle=PduHandle[476310],securityEngineID=null,securityModel=null,securityName=private,securityLevel=1,contextEngineID=null,contextName=null,retryMsgIDs=null], pdu=GETNEXT[requestID=476310, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.318.1.1.1.1.1.2 = Null]], messageProcessingModel=0, securityName=private, processed=true, peerAddress=192.168.120.20/37256, transportMapping=org.snmp4j.transport.DefaultUdpTransportMapping@16a362a3, tmStateReference=null]
2026-05-24 18:13:23,492 [DefaultUDPTransportMapping_0.0.0.0/161] DEBUG - [Util.ExtendedCommandProcessor.()] Successfull Connection

Synology
2026-05-24 18:29:35,601 [DefaultUDPTransportMapping_0.0.0.0/161] DEBUG - [Util.ExtendedCommandProcessor.()] got Request from:[B@b420132CommandResponderEvent[securityModel=1, securityLevel=1, maxSizeResponsePDU=2147483647, pduHandle=PduHandle[1113222366], stateReference=StateReference[msgID=0,pduHandle=PduHandle[1113222366],securityEngineID=null,securityModel=null,securityName=private,securityLevel=1,contextEngineID=null,contextName=null,retryMsgIDs=null], pdu=GET[requestID=1113222366, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.2.1.1.2.0 = Null]], messageProcessingModel=0, securityName=private, processed=true, peerAddress=192.168.120.64/44555, transportMapping=org.snmp4j.transport.DefaultUdpTransportMapping@16a362a3, tmStateReference=null]
2026-05-24 18:29:35,601 [DefaultUDPTransportMapping_0.0.0.0/161] DEBUG - [Util.ExtendedCommandProcessor.()] Successfull Connection

However, Synology gets more connections and readout that looks more OK than OpnSense.
I have saved 2 logs. One for OpnsSense NON-working and one from Synology workign.

Will try to investigate some more with debugging in Apcupsd.

I changed from private to public to separate some other SNMP that was going from Opn to Synology about disks and could see that it sends
the following but never gets any response (and could not find anything in the other logs to why:

1   0.000000   192.168.120.20   192.168.120.4   SNMP   89   161   get-next-request 1.3.6.1.4.1.318.1.1.1.2.2.6
2   2.007897   192.168.120.20   192.168.120.4   SNMP   89   161   get-next-request 1.3.6.1.4.1.318.1.1.1.3.2.3
9   4.019971   192.168.120.20   192.168.120.4   SNMP   89   161   get-next-request 1.3.6.1.4.1.318.1.1.1.3.2.2
10   6.030553   192.168.120.20   192.168.120.4   SNMP   89   161   get-next-request 1.3.6.1.4.1.318.1.1.1.4.1.1
15   8.037828   192.168.120.20   192.168.120.4   SNMP   89   161   get-next-request 1.3.6.1.4.1.318.1.1.1.2.2.4

Frame 1: Packet, 89 bytes on wire (712 bits), 89 bytes captured (712 bits)
Ethernet II, Src: 52:54:00:74:c0:6c (52:54:00:74:c0:6c), Dst: Intel_d5:60:9f (a0:36:9f:d5:60:9f)
Internet Protocol Version 4, Src: 192.168.120.20, Dst: 192.168.120.4
User Datagram Protocol, Src Port: 37743, Dst Port: 161
Simple Network Management Protocol
    version: version-1 (0)
    community: public
    data: get-next-request (1)
        get-next-request
            request-id: 514747
            error-status: noError (0)
            error-index: 0
            variable-bindings: 1 item
                1.3.6.1.4.1.318.1.1.1.2.2.6: Value (Null)
                    Object Name: 1.3.6.1.4.1.318.1.1.1.2.2.6 (iso.3.6.1.4.1.318.1.1.1.2.2.6)
                    Value (Null)

I have not changed the version on PowerShute. Only the OpnSense/plugins.

Also -d 99 did not give anything either. :-/
/usr/local/sbin/apcupsd -f /usr/local/etc/apcupsd/apcupsd.conf -d 99

//Dan Lundqvist