Abort flow if msg.payload doesn't exist

[Paul Reed]

I've written a flow that sends me a push message if my home network IP address changes (my provider has dynamic IP's!). Which is pretty useful for me at the moment until I sort out my domain, and also helps me with some networking problems.

It basically calls ipecho.com every 15 minutes, and compares the returned IP address with the previous one held in NodeRed (context.lastip).

Before I post it in Flows, I wanted to sort out a bug, where if ipecho.com fails to answer, it treats the blank msg.payload as being different to the last held IP address and sends an alert.

Can anyone suggest a very simple validity check, i.e 

'If msg.payload is blank, then abort the flow.'

Paul

[Paul Reed]

Sorry, the ipecho url is ipecho.net/plain not ipecho.com (too much coffee!!)

Paul

[Nicholas O'Leary]

Hi Paul,

You can use the Switch node to test the value of msg.payload and only pass it on if not null/blank.

Nick

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[Paul Reed]

Thanks Nick.

First time I've used 'Switch' and it's not such a simple little node as it's title suggests!

Pattern matching via Regex makes it easy to not just reject 'null's', but to positively filter IP addresses instead, which is infinitely better.

Paul

[Eugen Kammerloher]

Hi Paul,

I have the exact same situation.

I parse the Ip in a javascript node with this code:

context.lastIP = context.lastIP || 'first_run';

var ip = msg.payload.trim();

var ipformat = /^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/;

var msg1 = null;

if (ip.match(ipformat))

{

if (context.lastIP == 'first_run')

{

context.lastIP = ip;

}

if (context.lastIP != ip)

{

msg1 = {payload: ip, topic: "New IP obtained"};

}

}

else

{

msg1 = {payload: ip, topic: "Problems obtaining external IP"};

}

return msg1;

[Paul Reed]

Hi Eugen, thanks for the reply.

Our codes are very similar except I've used the switch node to contain the regex filter instead of building it into the javascript node, so your solution is probably a better option if you are familiar with javascript.

Paul