I want something to receive HTTP POSTs from another device
lazarus / 16-Databases

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Sheepdog · 2022-08-27 07:23

I think I can create an Arduino that will send HTTP "POST" messages
from time to time. (When the POST should be sent would be up to the
Arduino.)

I want to write something in Lazarus to run in a second computer. One
sitting on my LAN, standing by to receive POST messages.

Let's say the content of the POST is "At 21:45 temperature was 12.6
C".

I want the Lazarus program to append that to a text file held on the
hard drive of the computer the Lazarus program is running on.

(I can already write an app to add the contents of an edit box to a
text file (and clear the edit box) every time a user typed something
and then pressed Enter.)

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dje · 2022-08-27 07:44

You need TFPHTTPServer from the unit fphttpserver, which comes with
FreePascal.
There is an example here:
https://github.com/alrieckert/freepascal/blob/master/packages/fcl-
web/examples/httpserver/simplehttpserver.pas

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Sheepdog · 2022-08-27 11:41

Many thanks, dje! You've taken me further down the road, I think.

If others reading this want to do what I want to do, on a Windows
machine it SEEMS that you just rem out the wmecho library from the
"Uses" clause. (That WILL fix some things. I don't know that it
doesn't break others. I could find little on the web about wmecho...
anyone with information would do us all a favor by posting it here?

I've put other notes about my "one-eyed-king-with a blindfold on"
stmblings in the dark at...

https://trixiesgems.com/category/programming/lazarus/

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dje · 2022-08-27 12:16

If you haven't written http servers before, I think its best to start
with the simplest example, so you can see how this stuff actually
works. It is kinda fun.
So, start with a simple console server:
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
VerySimpleHttpServer; uses SysUtils, fphttpserver; type  
TMySimpleServer = class(TFPHttpServer)  public    procedure
HandleRequest(var ARequest: TFPHTTPConnectionRequest; var AResponse:
TFPHTTPConnectionResponse); override;  end;   procedure ShowMe(const
AName, AValue: string);  begin    WriteLn(AName, ': ', AValue); 
end;   procedure TMySimpleServer.HandleRequest(var ARequest:
TFPHTTPConnectionRequest; var AResponse: TFPHTTPConnectionResponse); 
begin    inherited;    ShowMe('Method', ARequest.Method);   
ShowMe('UserAgent', ARequest.UserAgent);    ShowMe('PathInfo',
ARequest.PathInfo);    ShowMe('Query', ARequest.Query);   
ShowMe('URL', ARequest.URL);    if Assigned(ARequest.QueryFields) then
begin      ShowMe('QueryFields', ARequest.QueryFields.CommaText);   
end;    if Assigned(ARequest.ContentFields) then begin     
ShowMe('ContentFields', ARequest.ContentFields.CommaText);    end;   
with AResponse.Contents do begin      Add('<HTML><BODY>');     
Add('<H1>Hello, World!<H1>');      Add('</BODY></HTML>');     
AResponse.ContentType := 'text/html';    end;  end; begin  with
TMySimpleServer.Create(nil) do begin    Port := 1234;   
WriteLn('Start HTTP Server');    Active := True;  end;end.The server
binds to port 1234, so run the server and pull up a browser and try
these URL's
http://localhost:1234/
http://localhost:1234/?apple=orange&lazarus=great
http://localhost:1234/?date=27/8/22&time=9:40&temp=cold
An example output on the console is:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Start HTTP
ServerMethod: GETUserAgent: Mozilla/5.0 (X11; Linux armv7l; rv:91.0)
Gecko/20100101 Firefox/91.0PathInfo: Query:
date=27/8/22&time=9:40&temp=coldURL:
/?date=27/8/22&time=9:40&temp=coldQueryFields:
date=27/8/22,time=9:40,temp=coldContentFields: Method: GETUserAgent:
Mozilla/5.0 (X11; Linux armv7l; rv:91.0) Gecko/20100101
Firefox/91.0PathInfo: /favicon.icoQuery: URL: /favicon.icoQueryFields:
ContentFields:
Its knda fun once you get started. Its just a matter of knowing what
data is being sent and where it is stored. But... Adding this to a GUI
is another story. The server needs to be threaded, and access to the
TForm's controls _must_ be synchronized.

Have fun.