怎么检测是否连上了网络？（包括在95/98/nt中）(50分)

借用unreal的回答
procedure TForm1.Button1Click(Sender: TObject);

function GetOnlineStatus : Boolean;
var ConTypes : Integer;
begin
ConTypes := INTERNET_CONNECTION_MODEM + INTERNET_CONNECTION_LAN + INTERNET_CONNECTION_PROXY;
if (InternetGetConnectedState(@ConTypes, 0) = False)
then Result := False
else Result := True;
end;

begin
if GetOnlineStatus then
ShowMessage(' Connected')
else ShowMessage(' not Connected');
end;

用ping 263.net之类的方法
看看能够ping通，不久知道了

to cactus123456:
请问：怎么得到INTERNET_CONNECTION_MODEM ,INTERNET_CONNECTION_LAN ,
INTERNET_CONNECTION_PROXY的值？并且好象InternetGetConnectedState也找不到
这个函数！

呵呵
uses WinINet;

这是源代码，拿分来。

procedure TForm1.Button1Click(Sender: TObject);
begin
if GetSystemMetrics(SM_NETWORK) AND $01 = $01 then
ShowMessage('Machine is attached to network') else
ShowMessage('Machine is not attached to network');
end;

to jsp:
我也很想把分给了你了事，但是。。。。
在我连上网的时候，这是可以用的，但我把网线拔了，它还是显示在网上，很显然。。。
你能不能改一改？

再问一下，怎么调用ping，怎么得到返回值，如果老是去ping的话，会不会被当成
恶意攻击？呵呵，我比较笨啦，还麻烦各位老大不吝指教！

有很多的低层的东西，值得一看。(connect to internet)

interface
uses
Windows, SysUtils, Registry, WinSock, WinInet;

type
TConnectionType = (ctNone, ctProxy, ctDialup);

function ConnectedToInternet : TConnectionType;
function RasConnectionCount : Integer;


implementation

//For RasConnectionCount =======================
const
cERROR_BUFFER_TOO_SMALL = 603;
cRAS_MaxEntryName = 256;
cRAS_MaxDeviceName = 128;
cRAS_MaxDeviceType = 16;
type
ERasError = class(Exception);

HRASConn = DWord;
PRASConn = ^TRASConn;
TRASConn = record
dwSize: DWORD;
rasConn: HRASConn;
szEntryName: Array[0..cRAS_MaxEntryName] Of Char;
szDeviceType : Array[0..cRAS_MaxDeviceType] Of Char;
szDeviceName : Array [0..cRAS_MaxDeviceName] of char;
end;

TRasEnumConnections =
function (RASConn: PrasConn; { buffer to receive Connections data }
var BufSize: DWord; { size in bytes of buffer }
var Connections: DWord { number of Connections written to buffer }
): LongInt; stdcall;
//End RasConnectionCount =======================


function ConnectedToInternet: TConnectionType;
var
Reg : TRegistry;
bUseProxy : Boolean;
UseProxy : LongWord;
begin
Result := ctNone;
Reg := TRegistry.Create;
with REG do
try
try
RootKey := HKEY_CURRENT_USER;
if OpenKey('/Software/Microsoft/Windows/CurrentVersion/Internet settings',False) then begin
//I just try to read it, and trap an exception
if GetDataType('ProxyEnable') = rdBinary then
ReadBinaryData('ProxyEnable', UseProxy, SizeOf(LongWord) )
else begin
bUseProxy := ReadBool('ProxyEnable');
if bUseProxy then
UseProxy := 1
else
UseProxy := 0;
end;
if (UseProxy <> 0) and ( ReadString('ProxyServer') <> '' ) then Result := ctProxy;
end;
except
//Obviously not connected through a proxy
end;
finally
Free;
end;

//We can check RasConnectionCount even if dialup networking is not installed
//simply because it will return 0 if the DLL is not found.
if Result = ctNone then begin
if RasConnectionCount > 0 then Result := ctDialup;
end;
end;

function RasConnectionCount : Integer;
var
RasDLL : HInst;
Conns : Array[1..4] of TRasConn;
RasEnums : TRasEnumConnections;
BufSize : DWord;
NumConns : DWord;
RasResult : Longint;
begin
Result := 0;

//Load the RAS DLL
RasDLL := LoadLibrary('rasapi32.dll');
if RasDLL = 0 then exit;

try
RasEnums := GetProcAddress(RasDLL,'RasEnumConnectionsA');
if @RasEnums = nil then
raise ERasError.Create('RasEnumConnectionsA not found in rasapi32.dll');

Conns[1].dwSize := Sizeof (Conns[1]);
BufSize := SizeOf(Conns);

RasResult := RasEnums(@Conns, BufSize, NumConns);

If (RasResult = 0) or (Result = cERROR_BUFFER_TOO_SMALL) then Result := NumConns;
finally
FreeLibrary(RasDLL);
end;
end;

谢谢各位的回答!!!

抱歉，楼了
uses WinInet;