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Takilara
Apprentice


Joined: 31 Jan 2002
Posts: 129
Location: Norway
PostPosted: Sun Mar 08, 2020 7:24 pm   

Set Content-Type: application/json with %url? or VBscript solution to post JSON
 
Hello,
I am trying to have CMUD (Pro) upload telemetry to a Thingsboard page.
I currently do this by having CMUD write out CSV files, and an external script monitoring these files, and push the telemetry to Thingsboard.

I would like to do this inside CMUD itself, and saw the %url function, and gave this a try.

I would like to be able to set the Content-Type header, but i cant seem to be able to get this to work. Seems regardless of what i do, the Content Type seems to be sent as application/x-www-form-urlencoded.

Is there a way to change the Header when using %url?

I have some other possible options lined up, and thoughts on these will also be welcome.

Option 1: Properly set Content-Type header on %url object, no external scripts or code required

Option 2: Somehow do this with VBScript or LUA

  • Would appreciate help on how to pass variables as parameters to a #FUNCTION defined as VBScript. (I have figured out how to get the VBScript to access CMUD variables by using the zvar, but i don't like the global nature of that)
  • I think this might be easier to do with #SCRIPT + %mss, at least then i seem to be able to pass arguments to the VBScript function, something i havent been able to figure out for #FUNCTION defined as VBScript


Option 3: Setup a lightweight singlepurpose webservice that responds to CMUD's %url.POST (application/x-www-form-urlencoded), properly encodes, and forwards as application/json to Thingsboard

All opinions are welcome:)
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Takilara
Apprentice


Joined: 31 Jan 2002
Posts: 129
Location: Norway
PostPosted: Sun Mar 08, 2020 9:31 pm   
 
Note that i have gotten this to work with JScript and WScript using zvar helper variable. JScript seem by far the cleanest.
(I am still curious about the %url function though...)

I put the below as an alias, using JScript
Code:

var token = "xxxxxxxxxxx";
$host = "http://127.0.0.1"
var port = 8080;
var telemetryUrl = host + ":" + port + "/api/v1/" + token + "/telemetry";

//construct json
//var xp = zvar.xp;
//var xpcost = zvar.xpcost;

// In CMUD, store the dbvar to a string var using
// #var js %json(dbvar)
// Then collect it in JScript by using
// var myvar = zvar.js

var testvar = zvar.js;

// for debug things, instanciate a WScript.Shell, then use shell.Popup()
//var shell = new ActiveXObject("WScript.Shell");
//shell.Popup(testvar);

var strJSONToSend = testvar;


xhr = new ActiveXObject("Microsoft.XMLHTTP");
xhr.open("POST", telemetryUrl, true);
xhr.setRequestHeader("Content-type", "application/json");
xhr.onreadystatechange = function () {
    if (xhr.readyState == 4 && xhr.status == 200) {
        //var json = JSON.parse(xhr.responseText);
        //console.log(json.email + ", " + json.name);
    }
}
xhr.send(strJSONToSend);
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shalimar
GURU


Joined: 04 Aug 2002
Posts: 4671
Location: Pensacola, FL, USA
PostPosted: Mon Mar 09, 2020 5:24 pm   
 
Hmm.. never got around to using %url myself, lots of options.
Try this?

$url=%url("http://127.0.0.1")
$url.Port=8080
$url.ContentType="some/string"

$post=$url.Post
#SHOW $post
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Takilara
Apprentice


Joined: 31 Jan 2002
Posts: 129
Location: Norway
PostPosted: Mon Mar 09, 2020 7:22 pm   
 
shalimar wrote:
Hmm.. never got around to using %url myself, lots of options.
Try this?

$url=%url("http://127.0.0.1")
$url.Port=8080
$url.ContentType="some/string"

$post=$url.Post
#SHOW $post


Thanks, It feels like that property is read only though.
$url.ContentType="application/json" give me "Access violation at address 0000000", while if i use
$url.Content-Type="application/json" I get "No method/property name: Content-type"

So apparently there is a method or property for ContentType. If i try to use it as ContentType("application/json"), I get illegal property.

Running the quoted script in the alias unmodified give the same Access violation

I suspect that the ContentType is only to read the return message? (indeed, it returns text/html on the server response when running towards a standard webserver)

I think it might be that i have to set this somehow in the Params or ParamStr properties...
(both of these are empty, i guess i can try some various permutations of contenttype="application/json" in those...)
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shalimar
GURU


Joined: 04 Aug 2002
Posts: 4671
Location: Pensacola, FL, USA
PostPosted: Mon Mar 09, 2020 10:01 pm   
 
I would get to trial and error with ample use of #SAY to see what is what.
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Takilara
Apprentice


Joined: 31 Jan 2002
Posts: 129
Location: Norway
PostPosted: Thu Mar 12, 2020 10:39 pm   
 
shalimar wrote:
I would get to trial and error with ample use of #SAY to see what is what.


I gave up on the %url Embarassed
I would assume it is possible to get it to what i wanted to do, however, since i had the working (almost) Jscript, i went down that path.

For info though:

  • using zvar.xxx in a JScript passes by reference, not by value, often borking the ZScript side of the variable. (in particular, i was using %json() to store the json string to a variable. After this getting passed to the JScript, the quotes in the JSON would be gone (this can happen even without the JScript also). I got this to work better by using zvar.xxxx.slice(0) to copy the variable
  • Due to some various pieces of weirdness in the %json method (I could not get it to work consistently for more than 10-20 times before it would start stripping quotes). I ended up writing my own #FUNC json, this works ok as long as it is a flat structure


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