There is limitation on how any open file handles (this includes sockets too) OS can support. If this limit is reached, you get above exception. If you are on ∗ nix OS, this can be easily increased.
I am on Ubuntu so for me I just execute following command from command line
sudo gedit /etc/security/limits.conf
and add following two lines
∗ soft nofile 3072
∗ hard nofile 3072
Save and Close the file. I don't know how to load these settings from command prompt but rebooting did the trick. To make sure these changes are done execute
If you know how to do it on windows please add comment.