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Como saber se estou conectado à internet?

Código

Interface 

uses 

Windows, SysUtils, Registry, WinSock, WinInet; 

type 

TConnectionType = (ctNone, ctProxy, ctDialup); 

function ConnectedToInternet : TConnectionType; 

function RasConnectionCount : Integer; 

implementation 

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 para receber dados da conexao} 

var BufSize: DWord; { tamanho em bytes do buffer } 

var Connections: DWord { numero de conexoes escritas no buffer } 

): LongInt; stdcall; 

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('SoftwareMicrosoftWindowsCurrentVersionInternet 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 

//Nao conectado com proxy 

end; 

finally 

Free; 

end; 

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;