インターネット接続確認をするには？ (ID：6307)

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本文

InternetOpenURLでキャッシュを取得するかどうかはちょっとテストしてみます。
結果は後ほど。

別の案を。
GetIfTableを使用すれば、LANの状態は見れそうです。
ダイアルアップの環境がないので、そちらのテストはできていませんが。

うちでは、接続されている場合は、dwOperStatusが5(MIB_IF_OPER_STATUS_OPERATIONAL)が返り、切断されている場合は、dwOperStatusが0(MIB_IF_OPER_STATUS_NON_OPERATIONAL)が返ってきました。

サンプルソースです。
//----------------------------------------------------
//関数の定義Unit
unit IPHLPAPI;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes;

Const
     MAX_INTERFACE_NAME_LEN             = $100;
     ERROR_SUCCESS                      = 0;
     MAXLEN_IFDESCR                     = $100;
     MAXLEN_PHYSADDR                    = 8;

MIB_IF_OPER_STATUS_NON_OPERATIONAL = 0 ;
     MIB_IF_OPER_STATUS_UNREACHABLE     = 1;
     MIB_IF_OPER_STATUS_DISCONNECTED    = 2;
     MIB_IF_OPER_STATUS_CONNECTING      = 3;
     MIB_IF_OPER_STATUS_CONNECTED       = 4;
     MIB_IF_OPER_STATUS_OPERATIONAL     = 5;

MIB_IF_TYPE_OTHER                  = 1;
     MIB_IF_TYPE_ETHERNET               = 6;
     MIB_IF_TYPE_TOKENRING              = 9;
     MIB_IF_TYPE_FDDI                   = 15;
     MIB_IF_TYPE_PPP                    = 23;
     MIB_IF_TYPE_LOOPBACK               = 24;
     MIB_IF_TYPE_SLIP                   = 28;

MIB_IF_ADMIN_STATUS_UP             = 1;
     MIB_IF_ADMIN_STATUS_DOWN           = 2;
     MIB_IF_ADMIN_STATUS_TESTING        = 3;

TYPE
   MIB_IFROW            = Record
         wszName              : Array[0 .. (MAX_INTERFACE_NAME_LEN*2-1)] of char;
         dwIndex              : LongInt;
         dwType               : LongInt;
         dwMtu                : LongInt;
         dwSpeed              : LongInt;
         dwPhysAddrLen        : LongInt;
         bPhysAddr            : Array[0 .. (MAXLEN_PHYSADDR-1)] of Byte;
         dwAdminStatus        : LongInt;
         dwOperStatus         : LongInt;
         dwLastChange         : LongInt;
         dwInOctets           : LongInt;
         dwInUcastPkts        : LongInt;
         dwInNUcastPkts       : LongInt;
         dwInDiscards         : LongInt;
         dwInErrors           : LongInt;
         dwInUnknownProtos    : LongInt;
         dwOutOctets          : LongInt;
         dwOutUcastPkts       : LongInt;
         dwOutNUcastPkts      : LongInt;
         dwOutDiscards        : LongInt;
         dwOutErrors          : LongInt;
         dwOutQLen            : LongInt;
         dwDescrLen           : LongInt;
         bDescr               : Array[0 .. (MAXLEN_IFDESCR - 1)] of Char;
  end;
  MIB_IFTABLE=record
    dwNumEntries: DWORD;
    table: Array[0 .. (MAXLEN_PHYSADDR-1)] of MIB_IFROW;
  end;
  PMIB_IFTABLE=^MIB_IFTABLE;

Function GetIfTable(
   pIfTable        : Pointer;
   VAR pdwSize     : LongInt;
   bOrder          : LongInt
   ): LongInt;  StdCall;

implementation

Function GetIfTable;          stdcall; external   'IPHLPAPI.DLL';

end.

//-----------------------------------------------------------
//こちらが使用例
uses
  IPHLPAPI;

procedure TForm1.Button1Click(Sender: TObject);
var
	Buf: array[0..1023] of char;
	d: Integer;
  IfTable: PMIB_IFTABLE;
  i: integer;
begin
  d := 0;

GetIfTable(nil, d, 0);
  IfTable := SysGetMem(d);

if Assigned(IfTable) then
  begin
		if  GetIfTable(IfTable, d,0) = NO_ERROR then
    begin
			for i := 0 to IfTable.dwNumEntries - 1 do
      begin
				Memo1.Lines.Add('');

Memo1.Lines.Add('dwIndex 0x' + IntToHex(IfTable.table[i].dwIndex, 8));
        case IfTable.table[i].dwType of
        MIB_IF_TYPE_OTHER:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_OTHER');
        MIB_IF_TYPE_ETHERNET:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_ETHERNET');
        MIB_IF_TYPE_TOKENRING:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_TOKENRING');
        MIB_IF_TYPE_FDDI:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_FDDI');
        MIB_IF_TYPE_PPP:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_PPP');
        MIB_IF_TYPE_LOOPBACK:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_LOOPBACK');
        MIB_IF_TYPE_SLIP:
          Memo1.Lines.Add('dwType MIB_IF_TYPE_SLIP');
        end;
				Memo1.Lines.Add('dwMtu ' + IntToStr(IfTable.table[i].dwMtu));
				Memo1.Lines.Add('dwSpeed ' + IntToStr(IfTable.table[i].dwSpeed));

Memo1.Lines.Add('dwPhysAddrLen ' + IntToStr(IfTable.table[i].dwPhysAddrLen));

Memo1.Lines.Add('bPhysAddr ' + 
					        IntToHex(Integer(IfTable.table[i].bPhysAddr[0]), 2) +
					        IntToHex(Integer(IfTable.table[i].bPhysAddr[1]), 2) +
					        IntToHex(Integer(IfTable.table[i].bPhysAddr[2]), 2) +
					        IntToHex(Integer(IfTable.table[i].bPhysAddr[3]), 2) +
					        IntToHex(Integer(IfTable.table[i].bPhysAddr[4]), 2) +
					        IntToHex(Integer(IfTable.table[i].bPhysAddr[5]), 2)
					);

Memo1.Lines.Add('dwAdminStatus ' + IntToStr(IfTable.table[i].dwAdminStatus));
				Memo1.Lines.Add('dwOperStatus ' + IntToStr(IfTable.table[i].dwOperStatus));
				Memo1.Lines.Add('dwLastChange ' + IntToStr(IfTable.table[i].dwLastChange));
				Memo1.Lines.Add('dwInOctets ' + IntToStr(IfTable.table[i].dwInOctets));
				Memo1.Lines.Add('dwInUcastPkts ' + IntToStr(IfTable.table[i].dwInUcastPkts));
				Memo1.Lines.Add('dwInNUcastPkts ' + IntToStr(IfTable.table[i].dwInNUcastPkts));
				Memo1.Lines.Add('dwInDiscards ' + IntToStr(IfTable.table[i].dwInDiscards));
				Memo1.Lines.Add('dwInErrors ' + IntToStr(IfTable.table[i].dwInErrors));
				Memo1.Lines.Add('dwInUnknownProtos ' + IntToStr(IfTable.table[i].dwInUnknownProtos));
				Memo1.Lines.Add('dwOutOctets ' + IntToStr(IfTable.table[i].dwOutOctets));
				Memo1.Lines.Add('dwOutUcastPkts ' + IntToStr(IfTable.table[i].dwOutUcastPkts));
				Memo1.Lines.Add('dwOutNUcastPkts ' + IntToStr(IfTable.table[i].dwOutNUcastPkts));
				Memo1.Lines.Add('dwOutDiscards ' + IntToStr(IfTable.table[i].dwOutDiscards));
				Memo1.Lines.Add('dwOutErrors ' + IntToStr(IfTable.table[i].dwOutErrors));
				Memo1.Lines.Add('dwOutQLen ' + IntToStr(IfTable.table[i].dwOutQLen));
				Memo1.Lines.Add('dwDescrLen ' + IntToStr(IfTable.table[i].dwDescrLen));

IfTable.table[i].bDescr[IfTable.table[i].dwDescrLen]:=#0;
				Memo1.Lines.Add('bDescr ' + IfTable.table[i].bDescr);
			end;
		end;
		SysFreeMem(IfTable);
	end;

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