Function output payload

General
1

Hello all.

This is probably really easy for somebody but I am struggling. I have read a bunch of stuff and never done any js stuff.

I am trying to use net-snmp in a function node. I need to eventually get snmp-v3 but for testing just v2.

I have it working so far and it returns the correct data in the debug window. But how do I get that same out put into the msg.payload?

Any help would be great. This is the code that I am running from the function node.

// NPM module exposed as variable, npm_module
var session = snmp.createSession ("192.168.10.250", "public");

var oids = ["1.3.6.1.2.1.1.1.0"];

session.get (oids, function (error, varbinds) {
    if (error) {
        console.error (error);
    } else {
        for (var i = 0; i < varbinds.length; i++) {
            if (snmp.isVarbindError (varbinds[i])) {
                console.error (snmp.varbindError (varbinds[i]));
            } else {
				console.log (varbinds[i].oid + " = " + varbinds[i].value);
            }
        }
    }
    session.close ();
});

return msg;
2

Firstly, is there a reason you are not using node-red-node-snmp?

Secondly, as you are running async code, you cannot return msg you need to use node.send

e.g....

// NPM module exposed as variable, npm_module
const session = snmp.createSession ("192.168.10.250", "public");
const oids = ["1.3.6.1.2.1.1.1.0"];

session.get (oids, function (error, varbinds) {
    if (error) {
        node.error(error, msg);
    } else {
        for (let i = 0; i < varbinds.length; i++) {
            const e = snmp.varbindError(varbinds[i]);
            if (e) {
                node.error(e, msg);
            } else {
                msg.payload = varbinds[i].value;
                msg.topic = varbinds[i].oid;
                node.send(msg)
            }
        }
    }
    session.close ();
});

/// return msg;  << delete this
3

Thanks for the reply.

I wasnt using node-red-node-snmp because as far as I am aware I couldnt do snmpV3 which is where this will end up.

Am just trying to get it working before I move forward.

As i said I have been reading and getting it to this point and have no js experiance so it has been a bit of a learning curve.

I have shut the pc down now but Will give the changes ago tomorrow.

Thanks again.

4

Ah. The node-red-node-snmp uses net-snmp under the hood (which does support v3) however its dependency is on a really old version.

There is a pull request to add V3 support but the PR author has not addressed the review comments (so the PR has stalled)