Mega Code Archive
How to check if I am connected to the internet
<![CDATA[
Title: How to check if I am connected to the 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;
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