A library upgrade (GWT 2.4.0 -> GWT 2.5.0) was necessary. Unfortunately newer version seems to cause more problems, than it actually solves.
A lot of "dead" connections (hundreds of them) are cumulating on server until it stops to respond. netstat -na gives the following result:
...
tcp 121 0 10.0.0.5:8181 XXX.XXX.XXX.XXX:4609 CLOSE_WAIT
...
It occurs only on GWT 2.5.0 and did NOT happen on GWT 2.4.0. No other changes in code. Unfortunately I'm unable to reproduce the problem locally. Both on my local environment and on server machine GlassFish 2.1.1 is used (and I'm stuck with it for now, however if that problem is somehow related to application server, it would still be great to know). The OS on server is Debian Squeeze 64-bit, locally I use Wheezy 32-bit.
In act of despair I added the filter with following code: httpServletResponse.setHeader("Connection", "close"); but with no result.
Do you have any ideas how to fix that OR how to track which connections are causing problem and when? Thanks!