.jco connection to ecc6

my application access diff. SAP systems...so i use jco as follow

com.sap.mw.jco.JCO.Client jcoclient =  com.sap.mw.jco.JCO.createClient ("client","user name","password","language","ip address","sys id");

jcoclient.connect();

but its working fine for 4.7 but not for ecc6, and i get a error as follow

<u>com.sap.mw.jco.JCO$Exception: (102) RFC_ERROR_COMMUNICATION: Connect to SAP gateway failed.</u>