Help: connecting to google map service using lNet
lazarus / 38-Networking and Web Programming

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Leledumbo · 2010-12-17 10:15

I'm trying to connect to a google map service, but the app hangs in
infinite loop. GoogleMapConnector.Connecting is never set to false
despite of the TimeOut property I set in the constructor.
Code: [Select]unit wmmain;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, HTTPDefs, websession, fpHTTP,
  fpWeb, lHTTP;

type

  { TMainWebModule }

  TMainWebModule = class(TFPWebModule)
    procedure TFPWebActions0Request(Sender: TObject; ARequest:
TRequest;
      AResponse: TResponse; var Handled: Boolean);
    procedure TFPWebActions1Request(Sender: TObject; ARequest:
TRequest;
      AResponse: TResponse; var Handled: Boolean);
    procedure DataModuleCreate(Sender: TObject);
    procedure DataModuleDestroy(Sender: TObject);
    function GoogleMapConnectorOnInput(ASocket: TLHTTPClientSocket;
ABuffer: pchar; ASize: integer): integer;
    procedure GoogleMapConnectorOnDoneInput(ASocket:
TLHTTPClientSocket);
  private
    { private declarations }
    GoogleMapConnector: TLHTTPClient;
    ResponseBuf: String;
  public
    { public declarations }
  end;

var
  MainWebModule: TMainWebModule;

implementation

{$R *.lfm}

const
  QueryStr = 'restoran';
  GoogleAPIKey = 'ABQIAAAAR16qAFe_aeUB7PXwb4ENZxRHYi30yMAYkyoiSwporea1
yo0xLRTg3lf_7VNbntYiWxJvDo5nIAW_SA';

{ TMainWebModule }

procedure TMainWebModule.TFPWebActions0Request(Sender: TObject;
  ARequest: TRequest; AResponse: TResponse; var Handled: Boolean);
begin
  AResponse.Content := '<p>Hello, World 1!</p>';
  Handled := true;
end;

procedure TMainWebModule.TFPWebActions1Request(Sender: TObject;
  ARequest: TRequest; AResponse: TResponse; var Handled: Boolean);
var
  StatusStr: String;
begin
  ResponseBuf := '';
  if GoogleMapConnector.Connect then begin
    while GoogleMapConnector.Connecting do Sleep(100);
    AResponse.Content := 'Respon:' +ResponseBuf;
  end else begin
    Str(GoogleMapConnector.Response.Status,StatusStr);
    AResponse.Content := Format('HTTP %s: %s',
      [StatusStr,GoogleMapConnector.Response.Reason]);
  end;
  Handled := true;
end;

procedure TMainWebModule.DataModuleCreate(Sender: TObject);
begin
  GoogleMapConnector := TLHTTPClient.Create(Self);
  with GoogleMapConnector do begin
    Timeout     := 10;
    Host        := 'http://maps.google.com';
    Port        := 80;
    URI         :=
Format('maps/geo?q=%s&output=json&oe=utf8&sensor=false' +
      '&key=%s',[QueryStr,GoogleAPIKey]);
    OnInput     := @Self.GoogleMapConnectorOnInput;
    OnDoneInput := @Self.GoogleMapConnectorOnDoneInput;
  end;
end;

procedure TMainWebModule.DataModuleDestroy(Sender: TObject);
begin
  GoogleMapConnector.Free;
end;

function TMainWebModule.GoogleMapConnectorOnInput(ASocket:
TLHTTPClientSocket;
  ABuffer: pchar; ASize: integer): integer;
var
  TempBuf: String;
begin
  SetString(TempBuf,ABuffer,ASize);
  ResponseBuf := ResponseBuf + TempBuf;
end;

procedure TMainWebModule.GoogleMapConnectorOnDoneInput(
  ASocket: TLHTTPClientSocket);
begin
  GoogleMapConnector.Disconnect;
end;

initialization
  RegisterHTTPModule('main', TMainWebModule);
end.
Btw, I'm behind a proxy. Do I need to set up anything?
Platform: i386-win32

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Leledumbo · 2010-12-17 12:59

Solved with Synapse

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JD · 2010-12-17 13:32

I'm glad to know that you got it to work. But I'm of the opinion that
Lazarus/FreePascal could do with small sample applications in the
following areas

a) Web applications using modern API's - Google, Skype, Amazon, IMDB
etc
b) Multitier database applications on LANs, WANs or the Internet
c) Graphics applications
d) Applications interacting with Java, Android, .NET etc
e) Applications showcasing Lazarus/FreePascal's reporting capabilities

In my opinion, these are the things necessary to convince corporate
decision makers that Lazarus/FreePascal is not a hobbyist' toy.

To many of us are reinventing the wheel again & again because
Lazarus/FreePascal does not have these "gotcha" sample apps.

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Dibo · 2010-12-17 13:33

1. lNET works on non-blocking mode. I'm not familiar in messages loop,
but I think your loop block lNET callback message in Application main
loop. Maybe Application.ProcessMessages solve this problem:
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 procedure
TMainWebModule.TFPWebActions1Request(Sender: TObject;  ARequest:
TRequest; AResponse: TResponse; var Handled: Boolean);var  StatusStr:
String;begin  ResponseBuf := '';  if GoogleMapConnector.Connect then
begin    while GoogleMapConnector.Connecting do     begin     
Sleep(100);      Application.ProcessMessages;    end;   
AResponse.Content := 'Respon:' +ResponseBuf;  end else begin   
Str(GoogleMapConnector.Response.Status,StatusStr);   
AResponse.Content := Format('HTTP %s: %s',     
[StatusStr,GoogleMapConnector.Response.Reason]);  end;  Handled :=
true;end;
But I'm not Application.ProcessMessages fan. If you want use non-
blocking sockets, you should change your TFPWebModule mechanism logic
to non-blocking too. For example - changing TFPWebActions1Request
procedure to Event property and call this event in
GoogleMapConnectorOnDoneInput

2. I don't know which version of lNET you are using, but Host property
was very sensitive for link format (like slash on end of link). In
demo, they using DecomposeURL function, which return Host without
"http://" prefix (maybe this is your problem). But be careful with
this function. I see you are using params in link. DecomposeURL cut
this params. So I written own DecomposeURL which include params in
link:
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 uses
URIParser; function TMyLHttpClient.MyDecomposeURL(const URL: string;
out Host, URI,  Params: string; out Port: Word): Boolean;var  uri_rec:
TURI;begin  Result := True;  uri_rec := ParseURI(URL, 'http', 80); 
Host := uri_rec.Host;  URI := uri_rec.Path + uri_rec.Document;  Params
:= uri_rec.Params;  Port := uri_rec.Port;end; 
Edit:
3. Maybe problem is in response code status. LHTTPClient is fine, but
to much "restricted". Each HTTP response code must be implemented in
source of LHTTPClient (se lhttp unit and HTTPStatusCodes const). If
google return uknown status, lHTTPClient hangs forever (OnDoneInput is
never called, no errors etc.). In mantis bugtracker is my patch wich
add some new codes, but not accepted yet.

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Leledumbo · 2010-12-18 15:58

QuoteGraphics applicationsThere are some in the application gallery
(and many more out there)
QuoteApplications interacting with Java, Android, .NET etcExcept for
Java, the other has entry in the wiki. I've tried JNI.pas bindings,
but it seems outdated and I can't make it to work with current Oracle
JDK.
QuoteApplications showcasing Lazarus/FreePascal's reporting
capabilitiesI remember a MRP application in the gallery.
QuotelNET works on non-blocking modeYeah, I know that because I
previously used it to create a chat application with many connections
involved and they run without waiting each other.
QuoteBut I'm not Application.ProcessMessages fan. If you want use non-
blocking sockets, you should change your TFPWebModule mechanism logic
to non-blocking tooThat seems a little inconvenient
QuoteI don't know which version of lNET you are using0.6.4
QuoteDecomposeURL cut this params. So I written own DecomposeURL which
include params in linkI haven't tried to print each host, port and uri
from DecomposeURL myself. But if it really cuts that, well... that's
disappointing.
QuoteMaybe problem is in response code status. LHTTPClient is fine,
but to much "restricted". Each HTTP response code must be implemented
in source of LHTTPClient (se lhttp unit and HTTPStatusCodes const). If
google return uknown status, lHTTPClient hangs forever (OnDoneInput is
never called, no errors etc.). In mantis bugtracker is my patch wich
add some new codes, but not accepted yet.Actually, that's not it. My
biggest problem is that I NEVER call SendRequest and in the waiting
loop I NEVER call CallAction. After that, I believe it works. But
since I have to pass through a proxy, it still fails. That's why I
moved to Synapse. Plus, the code is much shorter now. A lesson
learned: not every problem can be solved with component based approach
easily.