Java SMPP API

I'm not clear what's not working for you. Are you saying that after your application sends an enquire_link packet, that from that point onward the Connection fails to respond to enquire_link, deliver_sm packets received from the SMSC? Or does your application fail to send any further packets at all? Is this something to do with the autoAckLink functionality of the Connection?

You should turn on debug-level logging for the API to get more information about what is going on within it when the problem occurs for you. If you are using the logging config that comes with the API, you can achieve this by editing the log4j.properties file that comes with the API.