Win2000的网络断开是如何检测到的。

[blackfish]

在win2000中，只要把网线拔掉，在任务栏就会显示“网络电缆没有插好”，
它是怎么检测到的呢？是用API函数实现的吗？谁知道在delphi中如何可以实现
此功能，谢谢！！！！
[e-mail]

[cobi]

uses Winnet;

function isOnLan() : boolean;
var conType : DWORD;
begin
conType := INTERNET_CONNECTION_LAN;
result := InternetGetConnectedState(@ConTypes,0);
end;

[火鸟李国平]

GZ:)

[okhai]

???我也想知道，不过，好像上面说的是有没有联到互联网，
我想要求应该是局域网的连接状态吧。

[cobi]

最简单的方法是通过ping去判断，但是对于安装了防火墙的机器，这一招就不怎么好用了。

附：一个比较简单的ping例子
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, winsock;

type
TForm1 = class(TForm)
Memo1: TMemo;
Label1: TLabel;
Edit1: TEdit;
Button1: TButton;
procedure FormCreate(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
procedure ShowError(error: Integer);
public
{ Public declarations }
end;

PIPOptionInformation = ^TIPOptionInformation;
TIPOptionInformation = packed record
TTL: Byte; // Time To Live (used for traceroute)
TOS: Byte; // Type Of Service (usually 0)
Flags: Byte; // IP header flags (usually 0)
OptionsSize: Byte; // Size of options data (usually 0, max 40)
OptionsData: PChar; // Options data buffer
end;

PIcmpEchoReply = ^TIcmpEchoReply;
TIcmpEchoReply = packed record
Address: DWord; // replying address
Status: DWord; // IP status value (see below)
RTT: DWord; // Round Trip Time in milliseconds
DataSize: Word; // reply data size
Reserved: Word;
Data: Pointer; // pointer to reply data buffer
Options: TIPOptionInformation; // reply options
end;

TIcmpCreateFile = function: THandle; stdcall;
TIcmpCloseHandle = function(IcmpHandle: THandle): Boolean; stdcall;
TIcmpSendEcho = function(
IcmpHandle: THandle;
DestinationAddress: DWord;
RequestData: Pointer;
RequestSize: Word;
RequestOptions: PIPOptionInformation;
ReplyBuffer: Pointer;
ReplySize: DWord;
Timeout: DWord
): DWord; stdcall;

var
Form1: TForm1;

implementation

{$R *.DFM}

const
IcmpDLL = 'icmp.dll';

var
hICMPlib: HModule;
IcmpCreateFile : TIcmpCreateFile;
IcmpCloseHandle: TIcmpCloseHandle;
IcmpSendEcho: TIcmpSendEcho;
hICMP: THandle; // Handle for the ICMP Calls

procedure TForm1.FormCreate(Sender: TObject);
var
wsadata: TWSAData;
begin
// initialise winsock
if WSAStartup($101,wsadata) <> 0 then begin
ShowMessage('Error initialising Winsock');
halt;
end;

// register the icmp.dll stuff
hICMPlib := loadlibrary(icmpDLL);
if hICMPlib <> null then begin
@ICMPCreateFile := GetProcAddress(hICMPlib, 'IcmpCreateFile');
@IcmpCloseHandle:= GetProcAddress(hICMPlib, 'IcmpCloseHandle');
@IcmpSendEcho:= GetProcAddress(hICMPlib, 'IcmpSendEcho');
if (@ICMPCreateFile = Nil) or (@IcmpCloseHandle = Nil) or (@IcmpSendEcho = Nil) then begin
ShowMessage('Error loading dll functions');
halt;
end;
hICMP := IcmpCreateFile;
if hICMP = INVALID_HANDLE_VALUE then begin
ShowMessage('Unable to get ping handle');
halt;
end;
end
else begin
ShowMessage('Unable to register ' + icmpDLL);
halt;
end;
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
// Free icmp.dll
IcmpCloseHandle(hICMP);
FreeLibrary(hICMPlib);
// free winsock
if WSACleanup <> 0 then ShowMessage('Error freeing winsock');
end;

procedure TForm1.Button1Click(Sender: TObject);
const
Size = 56;
TimeOut = 3000;
var
Address: DWord; // Address of host to contact
HostName, HostIP: String; // Name and dotted IP of host to contact
Phe: PHostEnt; // HostEntry buffer for name lookup
BufferSize, nPkts: Integer;
pReqData, pData: Pointer;
pIPE: PIcmpEchoReply; // ICMP Echo reply buffer
IPOpt: TIPOptionInformation; // IP Options for packet to send
begin
// Do a lookup

Address := inet_addr(PChar(Edit1.Text));

if (Address = INADDR_NONE) then begin
Phe := GetHostByName(PChar(Edit1.Text));
if Phe = Nil then ShowError(WSAGetLastError)
else begin
Address := longint(plongint(Phe^.h_addr_list^)^);
HostName := Phe^.h_name;
HostIP := StrPas(inet_ntoa(TInAddr(Address)));
end;
end
else begin
Phe := GetHostByAddr(@Address, 4, PF_INET);
if Phe = Nil then ShowError(WSAGetLastError)
else begin
HostName := Phe^.h_name;
HostIP := StrPas(inet_ntoa(TInAddr(Address)));
end;
end;

if Address = INADDR_NONE then begin
Memo1.Lines.Add('Cannot resolve hostname ' + Edit1.Text);
end
else
begin
Memo1.Lines.Add('Sending ' + IntToStr(Size) + ' bytes to ' +
HostName + ' (' + HostIP + ')');

// Get some data buffer space and put something in the packet to send
BufferSize := SizeOf(TICMPEchoReply) + Size;
GetMem(pReqData, Size);
GetMem(pData, Size);
GetMem(pIPE, BufferSize);
FillChar(pReqData^, Size, $AA);
pIPE^.Data := pData;

// Finally Send the packet
FillChar(IPOpt, SizeOf(IPOpt), 0);
IPOpt.TTL := 64;
NPkts := IcmpSendEcho(hICMP, Address, pReqData, Size,
@IPOpt, pIPE, BufferSize, TimeOut);
if NPkts = 0 then ShowError(GetLastError)
else
begin
//ShowMessage('ok');
HostIP := StrPas(inet_ntoa(TInAddr(pIPE^.Address)));
Memo1.Lines.Add('Received ' + IntToStr(pIPE^.DataSize) +
' bytes from ' + HostIP +
' in ' + IntToStr(pIPE^.RTT) + ' msecs')
end;

// Free those buffers
FreeMem(pIPE);
FreeMem(pData);
FreeMem(pReqData);
end;
end;

procedure TForm1.ShowError(error: integer);
begin
Memo1.Lines.Add('Error: ' + IntToStr(error));
end;

end.

[blackfish]

1、当我在uses 段加上Winnet 后，总提示“File not found Winnet.dcu”错误，
在帮助里也没有InternetGetConnectedState ，这是API函数吗？
2、使用ping的方法可以暂时解决我的问题。
但是如果不知道其他机器的名字或ip，那又怎么检测呢？我看win2000里很快就检测
出来了，他应该不会老是去ping别人的机器吧。在插上网线是，网卡的灯会亮，win2000
会不会通过网卡的驱动来实现检测的呢？

[cccvvvttt]

给分了呀