program HelloWorldWebServerX;
 
//{$APPTYPE CONSOLE}
//#sign:Max: MAXBOX10: 05/02/2017 19:04:12 
 
//uses SysUtils, IdContext, IdCustomHTTPServer, IdHTTPServer;
 
//type TWebServer = class
  var FHTTPSrv: TIdHTTPServer;
  
  //@public
   procedure HTTPServerCommandGet(AContext: TIdPeerThread;
      ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo); forward;
 
procedure TWebServerCreate;
begin
  FHTTPSrv:= TIdHTTPServer.Create(Nil);
  //FHTTPSrv.DefaultPort:= 8080;
  with FHTTPSrv.Bindings.Add do begin
    IP:= '127.0.0.1';
    Port:= 8080;
  end;
  FHTTPSrv.OnCommandGet:= @HTTPServerCommandGet;
  FHTTPSrv.Active:= True;
end;
 
procedure TWebServerDestroy;
begin
  FHTTPSrv.Active:= False;
  FHTTPSrv.Free;
  //inherited Destroy;
end;
 
procedure HTTPServerCommandGet(AContext: TIdPeerThread;
          ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo);
begin
  AResponseInfo.ResponseNo:= 200;
  AResponseInfo.ContentType:= 'text/plain';
  AResponseInfo.ContentText:= 'Hello & Goodbye, maXbox World4!';
end;
 
begin   //@main
  TWebServerCreate;
  try
    Writeln('Hello world/Web server will start.. ');
    ShowMessageBig('maXbox Hello world/Web server'+#1310+
                          ' Press OK to quit webserver.'+#13);
    //Readln();
  finally
    TWebServerDestroy;
  end;
End.


ref:
  https://rosettacode.org/wiki/Hello_world/Web_server#Delphi
  add bindings & contenttype for more convention

Doc:

   HTTPServer1.Bindings.Add.IP := '127.0.0.1';
   HTTPServer1.Bindings.Add.Port := 50001;

This is a common newbie mistake. You are creating two bindings, one bound to 127.0.0.1:DefaultPort, and one bound to 0.0.0.0:50001. You need one binding instead, that is bound to 127.0.0.1:50001 instead.

with HTTPServer1.Bindings.Add do begin
  IP := '127.0.0.1';
  Port := 50001;
end;

call example:

procedure TDataFormbtnHTTPSendGetClick(Sender: TObject);
var
  HTTPClient : TIdHTTP;
  responseStream : TMemoryStream;
begin
  HTTPClient := TIdHTTP.Create(Nil);
  responseStream := TMemoryStream.Create;
  try
    try
      HTTPClient.Get1('http://127.0.0.1:8080', responseStream);
      responseStream.Seek(0, soFromBeginning);
      SetLength(Sr, responseStream.Size);
      responseStream.Read(Sr, responseStream.Size);
      writeln('response: '+sr)
      //writeln(': '+streamtoString3(responseStream))
    except 
      //on e : Exception do begin
      showmessage('Could not send get request to localhost, port 8080');
    end;
    //end;
  finally
    //FreeAndNil(HTTPClient);
    HTTPClient.Free;
    HTTPClient:= Nil;
    responseStream.Free;
  end;
end;


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