The web system determines the login of the same user from two locations

Write at login
<%
Rszt ("SSID") = session. sessionid 'database write session. sessionid prevents multiple user logins
Session ("SSID") = session. sessionid corresponds to a session ID when each client logs on.
'Write IP address and login user information
%>
Refresh check
<%
Set rs = server. Createobject ("ADODB. recordset ")
Rs. Open "select * From oa_ygdqzt where ygbh =" & SESSION ("uygbh"), Conn, 3, 2
If not Rs. EOF then
'Response. Write RS ("SSID") & "--" & SESSION ("SSID ")
Strip = RS ("userip ")
If RS ("SSID") <> SESSION ("SSID") then' is used to determine whether the user logs in elsewhere.
Response. Write "<script language = 'javascript '>"
Response. Write "alert ('this account is logged in on" & Strip & "and you are forced to log out. \ N if you have any questions, contact the administrator! ');"
Response. Write "window. Parent. Close ();"
Response. Write "</SCRIPT>"
End if
End if
Rs. Close
%>