TZoCInetChecker：检测网络连接的类

来源：作者：出处：巧巧读书 2006-11-26 进入讨论组

下面就是那时写的一个类TZoCInetChecker，提供了一个Method，几个Properties，还有几个Events，用起来和上面那个阻塞调用的函数一样方便，当然，它也包含了阻塞方式的检测：

方法

Execute：调用我就好了，其它的交给我去办

属性
    Busy：         我正忙着呢，还没检测完，一会儿再来
    AccessType：   你希望我怎么连接网络，直接连还是用代理？
    AsynRequest：同步检测的话我们要有一会儿看不到对方了，呜呜
    UserAgent：    想告诉Web服务器是阿猫还是阿狗在连接？在这里设置就好了
    Proxy：        让我用代理连网络，用哪个代理啊？
    Url：          原来是要检测这个地址能不能访问，保证办到

事件
    OnStart：      开始检测之前我会在这里通知你一声
    OnStatusChange：检测过程中发生什么事我会在这里及时通知你的
    OnComplete：    检测完成了，成功不成功我都会告诉你

{**********************************************************}
{                                                          }
{  TZoCInetChecker Component Version 1.00                  }
{                                                          }
{  Function: Asynchronously Check if a given web page      }
{            can be successfully retreived and feed back   }
{            the user with callback status infomation      }
{                                                          }
{                                                          }
{  This is a freeware. If you made cool changes on it,     }
{  please send them to me.                                 }
{                                                          }
{  Email: eagleboost@msn.com                               }
{  URL: http://www.ZoCsoft.com                             }
{                                                          }
{  History: + New Feature, - Removed, * Modified           }
{                                                          }
{           version 1.00 2005-06-03                        }
{             The first version                            }
{                                                          }
{**********************************************************}

unit ZoCInetChecker;

interface

uses
Windows, Messages, SysUtils, Classes, WinInet;

const
  INTERNET_STATUS_DETECTING_PROXY       = 80;
{$EXTERNALSYM INTERNET_STATUS_DETECTING_PROXY}
  WM_STATUSCHANGE                       = WM_USER + 200;
  WM_CHECKCOMPLETE                      = WM_USER + 201;

type
  LPINTERNET_ASYNC_RESULT = ^INTERNET_ASYNC_RESULT;
  INTERNET_ASYNC_RESULT = record
    dwResult: DWORD;
    dwError: DWORD;
  end;

  pREQUEST_CONTEXT = ^REQUEST_CONTEXT;
  REQUEST_CONTEXT = record
    hWindow: HWND;
    hOpen: HINTERNET;                   //HINTERNET handle created by InternetOpen
  end;

  TOnStatusChangeEvent = procedure(Sender: TObject; StatusCode: Cardinal) of object;
  TOnCompleteEvent = procedure(Sender: TObject; Connected: Boolean) of object;
  TAccessType = (atDirectConnect, atPreConfig, atPreConfigWithNoProxy, atProxy);

  TZoCInetChecker = class(TComponent)
  private
    { Private declarations }
    FUrl: string;
    FAccessType: TAccessType;
    FProxy: string;
    FOnStart: TNotifyEvent;
    FOnStatusChange: TOnStatusChangeEvent;
    FOnComplete: TOnCompleteEvent;
    FBusy: Boolean;
    hOpenUrl, hOpen: HINTERNET;
    FUserAgent: string;
    FWindowHandle: HWnd;
    iscCallback: INTERNET_STATUS_CALLBACK;
    RC: REQUEST_CONTEXT;
    FAsynRequest: Boolean;
    procedure WndProc(var Msg: TMessage);
  protected
    { Protected declarations }
    procedure DoOnStatusChange(StatusCode: Cardinal); dynamic;
  public
    { Public declarations }
    property Busy: Boolean read FBusy write FBusy;
    function Execute: Boolean;
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  published
    { Published declarations }
    property AccessType: TAccessType read FAccessType write FAccessType
      default atDirectConnect;
    property AsynRequest: Boolean read FAsynRequest write FAsynRequest
      default True;
    property UserAgent: string read FUserAgent write FUserAgent;
    property Proxy: string read FProxy write FProxy;
    property Url: string read FUrl write FUrl;
    property OnStart: TNotifyEvent read FOnStart write FOnStart;
    property OnStatusChange: TOnStatusChangeEvent read FOnStatusChange write
      FOnStatusChange;
    property OnComplete: TOnCompleteEvent read FOnComplete write FOnComplete;
  end;