So I created a simple ISAP server and a client that talks to it.

So I created a simple ISAP server and a client that talks to it. 
I followed this example
http://docwiki.embarcadero.com/RADStudio/XE6/en/Tutorial:_DataSnap_Application_Using_an_ISAPI_DLL_Server

Now here is the problem.
If I pass   firstName  as Joe+  then ISAPI server freaks out and I get  below error .

http/1.404 Not Found

Am I not supose to use  plus sign ( + ) with ISAPI strings  ??

Please advice. Thanks.