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Как проверить подключен ли компьютер к 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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