This page simply tests JmolSmilesApplet.jar. It just returns a value 1 or more if it finds a given pattern in the SMILES string; 0 if it doesn't, and -1 if there is an error processing the request.

find /: within SMILES:

all occurances
The commend that does this is simply:

 var retValue = document.getElementById("jmolSmiles1").find(pattern, smiles, asSmarts, isAll)

If -1 is returned, you can check for the cause using:

 alert(document.getElementById("jmolSmiles1").getLastError())

Documentation: SMARTS SMILES