EnquireLink, SmppTimeoutException

[DmitryTen]

Hi!

There is a question about EnquireLink
I use following code to maintain session:

		try {
			session.enquireLink(new EnquireLink(), TimeUnit.SECONDS.toMillis(10));
		} catch (SmppTimeoutException e) {
			log.error("elink exception", e);
			...
		}

It worked fine for few years, but from recent time i'm experiencing with SmppTimeoutException.
SmppTimeoutException is thrown, BUT tcpdump shows the response for EnquireLink was successfully received.

here it is StackTrace:
2018-03-22 08:51:26.475 ERROR [pool-21-thread-1] (ElinkTask.java:47) - elink exception
com.cloudhopper.smpp.type.SmppTimeoutException: Unable to get response within [10000 ms]
at com.cloudhopper.smpp.impl.DefaultSmppSession.sendRequestAndGetResponse(DefaultSmppSession.java:471)
at com.cloudhopper.smpp.impl.DefaultSmppSession.enquireLink(DefaultSmppSession.java:439)
at ru.cwt.message.utils.ElinkTask.run(ElinkTask.java:38)
...

here it is tcpdump request/response:

i use cloudhopper-smpp version 5.06.

Question is following:
Is this a known bug?
If it's not a bug, what could be a reason?
If it is a bug was it fixed in further versions?

Thanks a lot.
With Regards, Dmitriy.