check if I am connected to the internet?

Author: Simon Grossenbacher

Homepage: http://www.swissdelphicenter.ch

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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;