檢測IP是否同一網段

<%@LANGUAGE="JavaScript"%>
<%
function ip2hex(ip)
{
 var ip4 = ip.split(".");
 var p,i;
 var hexStr = "0x";
 for(i=0; i<ip4.length; i++)
 {
  p = new Number(ip4[i]);
  hexStr += p<16?("0"+p.toString(16)):p.toString(16);
 }
 return(hexStr);
}

function isSubNetIp(startIp,subCode,hostIp)
{
 startIp = ip2hex(startIp);
 subCode = ip2hex(subCode);
 hostIp = ip2hex(hostIp);
 return((startIp&subCode) == (hostIp&subCode));
}
//example:
Response.Write(isSubNetIp("221.209.108.138","255.255.255.0","221.209.108.140"));
%>