Writing a Web Client : how to code a request "POST" ? ....

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Writing a Web Client : how to code a request "POST" ? ....

Postby Jean-Pierre on Mon Nov 16, 2015 5:40 pm


I am automating search of information on the internet
it is to access the following website:

>>>> http://www.gatwickaviationsociety.org.u ... lookup.asp

then enter a code in the "Code S Mode" and click "Find"
(40643C, 391E0C, 3444CC, ....)
to retrieve the information about a given aircraft

the goal is to automatically make several searches.

with APL (under windows 7) I recover well the first page in the HTML variable, with the following command:

'www.gatwickaviationsociety.org.uk' QUERY 'GET /modeslookup.asp'

but how to simulate the input of the variable "Mode S Code" ???

I conducted an analysis of data that is sent when running in Firefox:
there is indeed a request "GET" to display the initial screen

then a request "POST" for the interrogation itself, with the following parameter:

POSTDATA MSC=40643C&Registration=&DICAOType=&DType=&DSerial=&DOperator=&DICAOOperator=&DSubOperator=&Submit2=Find
which has the effect of assigning a value to the variables of the HTML page: MSC Submit2

the "GET" requests are well described in the documentation (Interface Guide) but I found nothing about the "POST"

does this search is possible ?
how to proceed ?

I have made a few attempts, but I get systématiquenet the following message:
"HTTP Error 411. The request must be chunked gold-have a happy length"
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Joined: Wed Feb 15, 2012 10:55 am
Location: Yvelines - France

Re: Writing a Web Client : how to code a request "POST" ? ..

Postby Brian|Dyalog on Tue Nov 17, 2015 4:09 pm

Hi Jean-Pierre!

You can use HTTPCmd from the Samples namespace in Conga version 2.6 to issue any HTTP command (GET, POST, DELETE, etc). Conga version 2.6 was released coincident with Dyalog APL 14.1.

Code: Select all
      form←'MSC=40643C&Submit2=Find' ⍝ you need only supply the form inputs that have values
      z←('post' Samples.HTTPCmd) url form

1⊃z ⍝ 0 return code indicates success
2⊃z ⍝ second item in the result is a matrix of the response HTTP headers
http/1.1 200 ok
cache-control private
content-length 27917
content-type text/html
expires Tue, 17 Nov 2015 15:08:23 GMT
server Microsoft-IIS/7.5
x-powered-by ASP.NET
x-powered-by-plesk PleskWin
date Tue, 17 Nov 2015 15:08:22 GMT

The third element of the result is the actual data from the server, in this case, the HTML that makes up the response web page. You'll need to parse/examine this for the information you're looking for. I took a quick look, and the HTML that's returned is not particularly easy to transform into XHTML so that you could manipulate it with ⎕XML.

I noticed that Gatwick Aviation Society has a web service which offers several functions at http://www.gatwickaviationsociety.org.uk/ADControls/SiteLookups.asmx, however, I don't know if any of these provide the information you're looking for. The advantage of calling a web service is that the data returned is intended for processing under program control, rather than being HTML intended to be rendered by a browser.

I hope this helps!
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Location: West Henrietta, NY

Re: Writing a Web Client : how to code a request "POST" ? ..

Postby Jean-Pierre on Wed Nov 18, 2015 10:59 am

Hi Brian

thank you very much for that

I had thought of looking good in Conga, but I only have version 2.2 (Dyalog 13.1).
my search on the keyword "POST" is left unanswered

>>> Do I have the opportunity to access the version 2.6 Conga?

regarding the analysis of the result, I simply need to extract some strings for including it into my treatments.
all my programs are in APL, it will therefore have any problem.

I also thank you for the link to the "web service", but this is something totally new to me
I would have to spend a little time

immediately I will leave to use the only language I know: the APL

as I already mentioned, the work that I realize, are only for fun, a volunteer for an association that defends against aircraft disturbances

Posts: 7
Joined: Wed Feb 15, 2012 10:55 am
Location: Yvelines - France

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