How to load balance thick clients based on HTTP parameter?

what is the semicolon do when I used cid" 4 ";" ??

The syntax for findstr is:

findstr [source string] [search string] [skip count] [terminator character or count]

So:

findstr [HTTP::uri] "cid=" 4 32

says, find the part of the string that starts with "cid=" in the URI, skip 4 characters (the length of "cid="), and then move 32 characters up and stop. Now, if for example you had an X509::subject string:

CN=bob, OU=lab, DC=DOMAIN, DC=COM

And you wanted to grab the user's name, you'd use the character version of the terminator:

findst [X509::subject [SSL::cert]] "CN=" 3 ","