Delphi中用ICMP探測(cè)遠(yuǎn)程主機(jī)是否存活

2005-03-10 jlbnet

網(wǎng)絡(luò)通訊中經(jīng)常需要確定遠(yuǎn)程主機(jī)是否存活，以決定下一部進(jìn)行的操作?？梢灾苯邮褂肐CMP協(xié)議來實(shí)現(xiàn)，但是要考慮許多協(xié)議細(xì)節(jié)，實(shí)現(xiàn)起來比較麻煩。Windows 自帶的ICMP庫(kù)里有現(xiàn)成的函數(shù)可以使用，只要在使用前填充相應(yīng)的數(shù)據(jù)結(jié)構(gòu)就可以了。

以下是要使用的數(shù)據(jù)結(jié)構(gòu)。這些結(jié)構(gòu)MSDN里有C形式的聲明，這里給出的是Delphi的形式。

//用到的協(xié)議數(shù)據(jù)結(jié)構(gòu)
  PipOptionInfo = ^TIPOptionInfo; // IP 頭選項(xiàng)
  TIPOptionInfo = packed record
    TTL: Byte;//存活時(shí)間
    TOS: Byte;//Type of Service，請(qǐng)求類型
    Flags: Byte;//標(biāo)志
    OptionsSize: Byte;//選項(xiàng)長(zhǎng)度
    OptionsData: PChar;//選項(xiàng)數(shù)據(jù)
  end;
  PIcmpEchoReply = ^TIcmpEchoReply;
  TIcmpEchoReply = packed record  // ICMP 返回信息
    Address: DWord;//IP地址
    Status: DWORD;//狀態(tài)
    RTT: DWORD;
    DataSize: Word;//數(shù)據(jù)長(zhǎng)度
    Reserved: Word;//保留
    Data: Pointer;//數(shù)據(jù)
    Options: TIPOptionInfo;//選項(xiàng)區(qū)
  end;

//動(dòng)態(tài)庫(kù)中的函數(shù)聲明
  TIcmpCreateFile = function: THandle; stdcall; //創(chuàng)建ICMP句柄
  TIcmpCloseHandle = function(IcmpHandle: THandle): Boolean; stdcall; //關(guān)閉ICMP句柄
  TIcmpSendEcho = function(IcmpHandle:THandle; DestinationAddress:DWORD;
       RequestData:Pointer; RequestSize:Word; RequestOptions:PIPOptionInfo;
       ReplyBuffer:Pointer; ReplySize:DWord; Timeout:DWord):DWord; stdcall;//發(fā)送ICMP探測(cè)數(shù)據(jù)報(bào)

//要用到的變量聲明
  hICMPDll,hICMP:THandle;
  wsaData:TWSADATA;
  ICMPCreateFile:TICMPCreateFile;
  IcmpCloseHandle:TIcmpCloseHandle;
  IcmpSendEcho:TIcmpSendEcho;

//destip:要探測(cè)的遠(yuǎn)程地址，形如 192.168.1.1
PRocedure f_CheckOnline(destip:string);
var
  IPOpt:TIPOptionInfo;// 發(fā)包的 IP 選項(xiàng)
  IPAddr:DWORD;
  pReqData,pRevData:PChar;
  pIPE:PIcmpEchoReply;// ICMP Echo 回復(fù)緩沖區(qū)
  FSize: DWORD;
  MyString:string;
  FTimeOut:DWORD;
  BufferSize:DWORD;
  i:integer;
begin
  hICMPdll := LoadLibrary('icmp.dll'); //調(diào)取icmp 動(dòng)態(tài)庫(kù)
  if hICMPDll<>NULL then
  begin
    WSAStartup($101,wsaData);//初始化網(wǎng)絡(luò)協(xié)議棧
    @ICMPCreateFile := GetProcAddress(hICMPdll, 'IcmpCreateFile'); //取動(dòng)態(tài)庫(kù)中的導(dǎo)出函數(shù)
    @IcmpCloseHandle := GetProcAddress(hICMPdll, 'IcmpCloseHandle');
    @IcmpSendEcho := GetProcAddress(hICMPdll, 'IcmpSendEcho');
    hICMP := IcmpCreateFile; //創(chuàng)建 icmp句柄
 IPAddr:= inet_addr(PChar(destip)); //取要探測(cè)的遠(yuǎn)端主機(jī)ip地址
   
   FSize := 40;
   BufferSize := SizeOf(TICMPEchoReply) + FSize;
   GetMem(pRevData,FSize);
   GetMem(pIPE,BufferSize);
   FillChar(pIPE^, SizeOf(pIPE^), 0);
   pIPE^.Data := pRevData;
   MyString := 'Hi, OnLine?';//任意字符串
   pReqData := PChar(MyString);
   FillChar(IPOpt, Sizeof(IPOpt), 0);
   IPOpt.TTL := 64;
   FTimeOut := 500;//等待時(shí)長(zhǎng)
   i:=IcmpSendEcho(hICMP, IPAddr, pReqData, Length(MyString), @IPOpt, pIPE, BufferSize, FTimeOut);//如果有返回，返回值表示收到的回復(fù)的個(gè)數(shù)。如果為0表示沒有回復(fù)，主機(jī)無法到達(dá)
   FreeMem(pRevData);
   FreeMem(pIPE);
    IcmpCloseHandle(hicmp);
    FreeLibrary(hICMPdll);//釋放動(dòng)態(tài)庫(kù)
    WSAcleanup();//清理協(xié)議棧
  end;
end;