asp实现限制一个ip只能访问一次的方法

<% 
'///////////////////////////////////////////////////// 
'// // 
'//作用：一个ip地址只允许访问本页一次 // 
'//引用：<!-- #include file="check_ip.asp" --> // 
'// // 
'///////////////////////////////////////////////////// 

'response.charset = 936 '设置输出编码为简体中文 
'response.buffer = false '关闭缓冲区 

dim fso,ts,iplist,cfs 

'设置cookies函数 
function setcookie() 
response.cookies("isbrow") = "brow" 
response.cookies("isbrow").expires = date+365 
end function 

'记录ip地址函数 
function writeip(filename, ipaddress) 
set fso = server.createobject("scripting.filesystemobject") 
set ts = fso.opentextfile(server.mappath(filename),8,true) 
ts.writeline ipaddress 
ts.close 
set ts = nothing 
set fso = nothing 
end function 

'读取ip地址函数 
function readiplist(filename) 
set fso = server.createobject("scripting.filesystemobject") 
if not fso.fileexists(server.mappath(filename)) then 
createfile("iplist.txt") 
exit function 
end if 

set ts = fso.opentextfile(server.mappath(filename)) 
iplist = ts.readall 
ts.close 
set ts = nothing 
set fso = nothing 
readiplist = iplist 
end function 

'创建文件函数 
function createfile(filename) 
set fso = server.createobject("scripting.filesystemobject") 
set cfs = fso.createtextfile(server.mappath(filename)) 
cfs.close 
set cfs = nothing 
set fso = nothing 
end function 

'关闭当前ie窗口函数(注:ie6下通过,其他浏览器未测试) 
function closewindow() 
'response.write "<script>window.location='javascript:window.opener=null;window.close();'</script>" 
response.redirect "http://www.baidu.com" 
end function 

ip = request.servervariables("remote_addr") '获取浏览者ip地址 

cookie = request.cookies("isbrow") '获取当前cookies 
'response.write cookie 

if request.servervariables("http_x_forwarded_for") <> "" then 
response.write "本站不允许使用代理访问" 
response.end() 
else 
if cookie = "brow" then 
closewindow() 
else 
if instr(readiplist("iplist.txt"),ip) <> 0 then 
closewindow() 
else 
writeip "iplist.txt" , ip 
end if 
setcookie() 
end if 
end if 
%>