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Cannot connect to server: EMPTY RESPONSE

Posted: Fri Apr 24, 2015 2:48 pm
by sestores

I have several users running zimbra desktop (version 7.2.5) and most of them have no issues. We are connecting to a zimbra server (Version 8.6.0) running on CentOS in a VM.
I have had one user that has been getting this error occasionally: "Cannot connect to server". Clicking on the details shows "EMPTY RESPONSE"...
I can kill the zimbra process and re-launch it and everything is ok for a while, but then it happens again. Usually once or 2x a day.
This morning, I had one other user who had the same problem (so far just one time).


What should I be looking for?
This is causing me to pull my hair out. 


Cannot connect to server: EMPTY RESPONSE

Posted: Sat May 09, 2015 12:52 pm
by Dr_Agony
I'm having the same issue. Except that my users aren't using the Zimbra Desktop, they're logging in on the Internet. Most of my users have no issues at. One of my users says it happens so often that he can't even use his email.

I'm running Zimbra 8.6.0_GA_1153.FOSS.



I haven't found any help online to this problem. Is there an answer out there?

Cannot connect to server: EMPTY RESPONSE

Posted: Wed May 27, 2015 9:28 am
by Javier Garcia Alarcon
Hello all. One of my customers have the same issue. Sometimes, not the same client, says that long response time to the server has been detected and cuts the connection.

Latency to the server is about 60ms, max imap copnnections are 400 (there are about 200) and we dont see any lost packet in the connection.

Any idea?

Best regards

Cannot connect to server: EMPTY RESPONSE

Posted: Wed May 27, 2015 9:29 am
by Javier Garcia Alarcon
Sorry, Centos 6.5 ZOS 8.6 Patch 2 12 Gb Ram 2 CPU DL 360

Cannot connect to server: EMPTY RESPONSE

Posted: Wed May 27, 2015 10:46 am
by jorgedlcruz
Hi Javier, guys,

The Zimbra Desktop 7.2.7 Release is in Beta and will be available pretty soon, let us know when is public if fix this problem.



Best regards

Cannot connect to server: EMPTY RESPONSE

Posted: Wed May 27, 2015 10:48 am
by Javier Garcia Alarcon
Hi Jorge... Bu this problem is, in my case, not only from client... webmail have issues too and some thunderbid gives similar messages... i am whitelisting ip in dosfilter to see if it's the problem...

Cannot connect to server: EMPTY RESPONSE

Posted: Wed May 27, 2015 10:52 am
by Javier Garcia Alarcon
I see...



2015-05-27 17:50:39.426:WARN:oejs.DoSFilter:qtp2047526627-9642:https://a.b.c.d:443/service/home/~/?auth=co&id=3313&part=8&t=1432741840665: DOS ALERT: Request rejected ip=a.b.c.d,session=1mfp9dt8048v41jomh21hq2wf4,user=null

2015-05-27 17:50:39.451:WARN:oejs.DoSFilter:qtp2047526627-9640:https://zimbraserverip:443/service/home/~/?auth=co&id=3313&part=2&t=1432741840638: DOS ALERT: Request rejected ip=zimbraserverip,session=1mfp9dt8048v41jomh21hq2wf4,user=null

2015-05-27 17:50:39.475:WARN:oejs.DoSFilter:qtp2047526627-9639:https://1zimbraserverip:443/service/home/~/?auth=co&id=3313&part=2&t=1432741840635: DOS ALERT: Request rejected ip=a.b.c.d,session=1mfp9dt8048v41jomh21hq2wf4,user=null

2015-05-27 17:50:39.476:WARN:oejs.DoSFilter:qtp2047526627-9643:https://zimbraserverip:443/service/home/~/?auth=co&id=3313&part=3&t=1432741840642: DOS ALERT: Request rejected ip=a.b.c.d,session=1mfp9dt8048v41jomh21hq2wf4,user=null

Cannot connect to server: EMPTY RESPONSE

Posted: Fri May 29, 2015 10:19 am
by sestores
Javier, I agree. I think we are only seeing this on the Desktop client because most of our users are using it.

I have read others with the same issue on the webmail client. Our webmail client only gets light usage.

Cannot connect to server: EMPTY RESPONSE

Posted: Fri May 29, 2015 11:15 am
by Javier Garcia Alarcon
Hi all

I ve changed Max Imap Sessions to a upper value and the problem does not dissapear but, after a log an documentation research i Think that perhaps is the DosFilter... why? well....Really the problem appears usually most times early in the morning and after lunch about 15 pm so I think that perhaps the trigger is the amount of new open sessions for time unit. Suddenly every people connect and DosFilter stop them from a number of connections in time unit. I ve changed this whitelisting the ip (a large number of sessions come from the same IP) in DosFilter and after two days i have no notices of new issues... i will wait a week and if the problem has dissapeared i will think that this is the origin. I will say you...

Cannot connect to server: EMPTY RESPONSE

Posted: Tue Sep 15, 2015 11:44 am
by thenodemaster
Pardon my question, but where do you find the Max IMAP Sessions option (path and config file)? I think this is what is happening with our server as well and would like to test that theory. Thanks!