HTTP Control of device on local network - HTTP request POST

[MarkC]

Hi all,
I am trying to control a device on my local network via the HTTP request node and POST option - but getting the '404 page not found' error below, regardless what I try:

The control documentation for the device only provides the following instructions for HTTP control:

The device is already set to 'HTTP control' and I can successfully read parameters via the HTTP request node and GET option, the issue is only with writing/control (using the POST option).

This is one of the many arrangements that I have tried, but I am guessing a little here based on other examples I have found.

I have spent a few hours looking through the Node-RED documentation, various online videos and this forum, but unable to resolve the issue (there is actually not so much info about the POST option) - so would greatly appreciate any pointers.

Many thanks in advance, Mark.

[mudwalker]

I have found that if you can access the page from a Web Browser (I can only speak of Chrome or Firefox), go to Web Developer Tools | Network and look at the message sent when you access the page, this will hopefully give some indication of the requirements to access the page (Method, Headers etc.)

[Colin]

Are you sure it has to be a post? Do the docs say that? What happens if you put that URL in a browser?

[MarkC]

Hi @Colin thanks for the reply.

No I'm not sure at all that it needs to be a 'post' command, that just seemed logical to me and I saw it used elsewhere - if you have another suggestion I am very willing to try it.

If I put in the URL of IP/control.html the following page displays

[MarkC]

Hi @mudwalker, thanks for the reply and suggestion.
Yes I can access the web page at [IP]/control.html with Chrome browser and access the web developer tools - I have looked under 'Network' and reloaded the page but not too sure what to look for...

These are a few screen images, please let me know if there is anything of interest there.

Regards, Mark.

[dceejay]

so did you try it with a GET instead ? using the .../control.html?power=n as per you initial config.

[MarkC]

Hi @dceejay, no not for anything on the control page yet, only to retrieve data from the IP/data.jsn page. Let me try that now...
Regards, Mark.

[MarkC]

Using the GET command and IP/control.html?power=n as the URL I basically get back what is on that web page - see screen image

And if I use only IP/control.html as the URL I get exactly the same response back.

[dceejay]

Well I would expect n to be a number eg of some device or other... read the manual

[Colin]

@MarkC

If I put in the URL of IP/control.html

I meant to use the url that the docs say, so http://IP/control.html?power=n where n is presumably a number.

[MarkC]

Hi @Colin and @dceejay,
Yes 'n' is the desired power output - a number between 0 and 3000.

I just got it to work with the GET option and entering the desired power direct into the URL. I will make that work dynamically next. What would be the best way, using {{{payload}}} in place of n?

I actually tried this a little earlier but had no load plugged in, and because of that there was no feedback - the power always remained as 0 (despite receiving the command). Now that I plugged a load in the power as displayed in that page changes (and the load activates).

Thank you both very much, your help is greatly appreciated!

Regards, Mark.

[TotallyInformation]

@MarkC

What would be the best way, using {{{payload}}} in place of n ?

Yes, but you can use 2 brackets rather than 3, that's to pass unencoded HTML and you don't need to do that here.

[MarkC]

Thank you @TotallyInformation - it's all working nicely and I am happy now!