Accessing Arduino Wifi
lazarus / 38-Networking and Web Programming

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Serge58 · 2017-08-06 20:38

Hello,
I am trying to send some data to my arduino micro controller wifi. 
This thing act as a server on my home wireless network but requires
specific (and i guess proprietary) commands.

For exemple, if I write the following in the address box a regular web
browser while connected to the home network: 
 http://10.0.4.1/arduino/webserver it is a valid command for the
Arduino. I can also write something similar to
http://10.0.4.1/arduino/analog/1/23 and it is also valid.  This tells
the Arduino Microcontroller to set its analog output 1 to 23.  Very
basic.

How can I send the same type of commands through a Lazarus routine?
Also, after receiving the command, Arduino will send back very simple
html data to share the status of its inputs ports.
I will have to be able to read it back in some way before processing
it.

Help required.

many thanks,

Serge

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Almir.Bispo · 2017-08-06 20:46

Hi.
You need use Synapse library with HTTPSend unit on Desktop

Just do this method
HTTPSend.GetText('url' , stringlist);

(*url is the server and parameter to your server like this:
http://arduinoserver?param1=data1&param2=data2)
stringlist is a Tstringlist class.It must be created on runtime.

On Arduino code you must get the params to do something.
http://adltecnologia.blogspot.com.br

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molly · 2017-08-06 21:33

Quote from: Serge58 on August 06, 2017, 10:38:49 pmHello,
I am trying to send some data to my arduino micro controller wifi.
...
How can I send the same type of commands through a Lazarus routine?
Also, after receiving the command, Arduino will send back very simple
html data to share the status of its inputs ports.
I will have to be able to read it back in some way before processing
it.

You could perhaps use something like this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
arduino;uses  fphttpclient;var  s: string;begin  s :=
TFPCustomHTTPClient.SimpleGet('http://10.0.4.1/arduino/webserver'); 
WriteLn(s);  // or something like: memo1.Lines.Add(s);end. 
See also here.

You would need to process the returned html body manually though.

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Serge58 · 2017-08-06 22:55

Thanks both of you.
I installed the synapse package.  I was getting some errors and found
on the net that I had to disable a line of code in one of the unit. 
After the package seems to be installed properly. No error.

i tried both of your options:  First, HTTPSend.GetText is giving me
some error.  i checked and it seems that there is no GetText method in
the HTTPSend class.

On the fphttpclient option i do not get error.  But it is not sending
data (i think) and does nothing.  i have to stop it.

is it possible that i needed to specify the port number somewhere?  I
saw that there are many fphttpclient versions.  Is this one part of
the same synapse package?

Thanks both of you.

my code:

// Button 2 "Using fphttpclient"
procedure TForm1.Button2Click(Sender: TObject);
  var
  str: String;
begin
   str :=
TFPCustomHTTPClient.SimpleGet('http://10.0.4.1/arduino/webserver');
   ShowMessage(str);
end;
// Button 1 using "HTTPSend"
procedure TForm1.Button1Click(Sender: TObject);
   var
   str: String;
   Param: TStringlist;
begin
   Str:='http://1.0.4.1/arduino/webserver';
   HTTPSend.GetText (Str , Param);
   ShowMessage('Param);
end;

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molly · 2017-08-06 23:15

Quote from: Serge58 on August 07, 2017, 12:55:15 amOn the fphttpclient
option i do not get error.  But it is not sending data (i think) and
does nothing.  i have to stop it.
That is strange. I have no idea atm.

edit: in case you are running this compiled program on Windows, do you
perhaps have antivirus/firewall running that blocks your lazarus
application ?

In theory tfphttclient.SimpleGet should only 'hang' for the duration
of timeout and return on errors (in which case the resulting body
should be able to provide more information).

Quoteis it possible that i needed to specify the port number
somewhere?
That is possible.I'm sorry but do not know much about arduino
webserver. It should state somewhere what are the default options.

SimpleGet just sends data to the server at port 80. Perhaps arduino
expects another port, such as 8080 ? Or perhaps the server only
accepts secure connections ?

QuoteI saw that there are many fphttpclient versions.  Is this one
part of the same synapse package?
fphttpclient is part of fcl-web and is a native/default Free Pascal
package.

In case your server is redirecting then simpleget will not work as you
expected. In that case have a look at the link i posted in my previous
post and use the 'full' version of retrieving a html page from your
server. SimpleGet class method is only meant to work in/for the most
simplest of conditions.

In case you wish to learn more about the data sending/retrieval 
between browser and server then you could consider using a proxy
server. But there are also other options available that would let you
inspect datapackets and/or http transfers.


edit2: I do not know much about synapse but i read:
Quote from: Serge58 on August 07, 2017, 12:55:15 am 
 Str:='http://1.0.4.1/arduino/webserver';
Copy-paste error or actual typo in your code (for the web-address) ?

edit3:
Quote from: Serge58 on August 07, 2017, 12:55:15 ami tried both of
your options:  First, HTTPSend.GetText is giving me some error.  i
checked and it seems that there is no GetText method in the HTTPSend
class.
Seems to me that user Almir.Bispo only got it partially correct.
According to this online help for synapse, it should read:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
synapsing;Uses  HTTPSend;var  url: String;  Response:
TStringlistbegin  url := 'http://10.0.4.1/arduino/webserver'; 
Response := TStringList.Create;  if httpGetText (url , Response)    
then ShowMessage(Reponse.text)    else ShowMessage('Failure'); 
Response.free;end.

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Serge58 · 2017-08-07 01:40

Thanks a million!!
With your help I was able to make it work.  First, my Url was bad.  It
should have read 10.0.1.4. Thanks for pointing it out.

My code:
// Button 1 using 'HTTPSend'

procedure TForm1.Button1Click(Sender: TObject);
  var
  url,html: String;
begin
  url:= 'http://10.0.1.4/arduino/webserver';
  html := TFPCustomHTTPClient.SimpleGet(url);
    memo1.Text := html;
end;

// Button 2 Using 'fphttpclient'

procedure TForm1.Button2Click(Sender: TObject);
  var
  httpclient: TFPHTTPClient;
  html,url: String;
begin
  url:= 'http://10.0.1.4/arduino/webserver';
  httpclient:= TFPHttpClient.Create(Nil);
  try
     html:= httpclient.Get(url);
  finally
     httpclient.Free;
  end;
  memo1.Text := html;
 end;  

Both of the functions are working.
many thanks,