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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;

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Detalhes da dica

Categoria: Rede
Adicionada dia: 06/06/03
Por: Felipe Monteiro
Visualizada: 4866 vezes

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