//检查一个URL是否有效函数

//可用来检测网络连接是否正确，InternetCheckConnection函数检查不准确，有些情况无法检测到，而以下CheckUrl函数则不会。

//uses wininet;

function CheckUrl(url: string): Boolean;

var

hSession, hfile, hRequest: hInternet;

dwindex, dwcodelen: dword;

dwcode: array[1..20] of Char;

res: PChar;

begin

Result := false;

if Pos(´http://´, LowerCase(url)) = 0 then url := ´http://´ + url;

hSession := InternetOpen(´InetURL:/1.0´, INTERNET_OPEN_TYPE_PRECONFIG,

nil, nil, 0);

if Assigned(hsession) then

begin

hfile := InternetOpenUrl(hsession, PChar(url), nil, 0, INTERNET_FLAG_RELOAD, 0);

dwIndex := 0;

dwCodeLen := 10;

HttpQueryInfo(hfile, HTTP_QUERY_STATUS_CODE, @dwcode, dwcodeLen, dwIndex);

res := PChar(@dwcode);

Result := (res = ´200´) or (res = ´302´); //200,302未重定位标志

if Assigned(hfile) then

InternetCloseHandle(hfile);

InternetCloseHandle(hsession);

end;

end;