too many files open

[IvanKucherov]

Environment: Tangobox 9.3.
Actions:

1. Connect to TangoTest server with atkpanel: atkpanel sys/tg_test/1
2. Check connections of TangoTest: lsof | grep TangoTest | grep ESTABLISHED
   Or lsof | grep TangoTest | grep ESTABLISHED -c - gives number of lines found.

Result:
Number of open connections grows.
After few days it reaches limit of open files and user cannot connect to tg_test.
If close atkpanel, lsof | grep TangoTest | grep ESTABLISHED -c returns 0.

Same issue on my custom device server leads to situation when it cannot open TCP connection to hardware, paralyzing operation of my system.