SAP JCo - Connection to SAP server using external/public IP

Problem:

JCo to SAP gateway connection fails when you are connecting to SAP gateway using an external or public IP which is NATed to an internal IP.

Solution:

1.Need to add a parameter gw/alternative_hostnames and enter the external or public IP value to the default profile.

2.Use SAPGLOBALHOST name as ASHOST value