判断网络连接状态的问题(掉线、已连接)

Question

做个小程序想随时高效的判断网络是否 掉线 和 已经连接上 ，请问应该怎么处理？
网络上的答案就不要给了，全试了个遍，没一个考虑得全面且实用！
谢谢！

Answer 1

除了ping外还有别的方法可行吗？

Answer 2

使用socket连接到服务器，如果连接不上说明网络断了

Answer 3

使用心跳机制，定时ping，判断。改变托盘图标。显示连接状态。 

Answer 4

第一步API IsNetworkAlive() 能返回当前网络连接状态。（仅连接状态哦）
   NETWORK_ALIVE_LAN  内网OK
   NETWORK_ALIVE_WAN  公网OK（仅限于类似ADSL拨号直连连接）第二步
  const ROUTE_TO_GOOGLE = $04040404;
  GetBestInterface(ROUTE_TO_GOOGLE, @dwInterfaceIndex);
  如果这个返回网络接口了，那说明有网卡可以通向Google，那基本说明网络OK了第三步
  还不放心的话，上PING吧

Answer 5

自己写心跳。
现在的大型MMO游戏都这么做。

Answer 6

function Ping(IP:string):boolean; overload;//uses WinSock
function Ping(IP:string):Boolean;
const
  IcmpVersion=102;
  IcmpDLL='icmp.dll';
type
  TIcmpCreateFile=function:THandle;stdcall;
  TIcmpCloseHandle=function(IcmpHandle:THandle):Boolean;stdcall;
  TIcmpSendEcho=function(IcmpHandle:THandle;
    DestinationAddress:DWORD;
    RequestData:Pointer;
    RequestSize:Word;
    RequestOptions:Pointer;
    ReplyBuffer:Pointer;
    ReplySize:DWord;
    Timeout:DWord
    ):DWord;stdcall;
var
  hICMPdll:HModule;// Handle for ICMP.DLL
  hICMP:THandle;
  IcmpCreateFile:TIcmpCreateFile;
  IcmpCloseHandle:TIcmpCloseHandle;
  IcmpSendEcho:TIcmpSendEcho;
  wsa:TWSAData;
  rep:array[1..128] of byte;
  InAddr2:DWORD;//InAddr1: TInAddr;
  phe:PHostEnt;// HostEntry buffer for name lookup
  pac:PChar;
  dwRet:DWORD;
  bValidIP:Boolean;
begin
  Result:=False;
  try
    if WSAStartup($101,wsa)<>0 then exit;
    bValidIP:=False;
    InAddr2:=0;
    phe:=GetHostByName(PChar(IP));
    if Assigned(phe) then
    begin
      pac:=phe^.h_addr_list^;
      if Assigned(pac) then
      begin
        InAddr2:=LongInt(PLongInt(phe^.h_addr_list^)^);
        bValidIP:=True;
      end;
    end;
    if bValidIP then
    begin
      hICMPdll:=LoadLibrary(icmpDLL);
      if hICMPdll>0 then
      begin
        @ICMPCreateFile:=GetProcAddress(hICMPdll,'IcmpCreateFile');
        @IcmpCloseHandle:=GetProcAddress(hICMPdll,'IcmpCloseHandle');
        @IcmpSendEcho:=GetProcAddress(hICMPdll,'IcmpSendEcho');
        if (@ICMPCreateFile<>nil)and(@IcmpCloseHandle<>nil)and(@IcmpSendEcho<>nil) then
        begin
          hICMP:=IcmpCreateFile;
          if hICMP<>INVALID_HANDLE_VALUE then
          begin
            dwRet:=IcmpSendEcho(hICMP,InAddr2,nil,0,nil,@rep,128,0);
            Result:=(dwRet<>0);
//            if hICMP<>INVALID_HANDLE_VALUE then
            IcmpCloseHandle(hICMP);
          end;
         // if hICMPdll<>0 then
          FreeLibrary(hICMPdll);
        end;
      end;
    end;
  finally
    WSACleanup;
  end;
end;