可以看看这个方法（我从其他地方抄的）
{判断网络连接，Delphi没有封装这个方法，所以可以参考MSDN里的介绍}
Function CheckNet(IpAddr: string): Boolean;
type
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;
const
Size = 32;
TimeOut = 1000;
var
wsadata: TWSAData;
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
const
IcmpDLL = 'icmp.dll';
var
hICMPlib: HModule;
IcmpCreateFile : TIcmpCreateFile;
IcmpCloseHandle: TIcmpCloseHandle;
IcmpSendEcho: TIcmpSendEcho;
hICMP: THandle; // Handle for the ICMP Calls
begin
// initialise winsock
Result:=True;
if WSAStartup(2,wsadata) <> 0 then begin
Result:=False;
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
Result:=False;
halt;
end;
hICMP := IcmpCreateFile;
if hICMP = INVALID_HANDLE_VALUE then
begin
Result:=False;
halt;
end;
end
else
begin
Result:=False;
halt;
end;
// ------------------------------------------------------------
Address := inet_addr(PChar(IpAddr));
if (Address = INADDR_NONE) then
begin
Phe := GetHostByName(PChar(IpAddr));
if Phe = Nil then Result:=False
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 Result:=False;
end;
if Address = INADDR_NONE then
begin
Result:=False;
end;
// 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 Result:=False;
// Free those buffers
FreeMem(pIPE);
FreeMem(pData);
FreeMem(pReqData);
// --------------------------------------------------------------
IcmpCloseHandle(hICMP);
FreeLibrary(hICMPlib);
// free winsock
if WSACleanup <> 0 then Result:=False;
end;
