This script will remove all existing close-wait connections on the server
$ apt-get install libnet-rawip-perl libnet-pcap-perl libnetpacket-perl
$ ./kill_close_wait_connections.pl
To install permanently you can do the following:
$ mv kill_close_wait_connections.pl /usr/bin/kill_close_wait_connections
$ chmod +x /usr/bin/kill_close_wait_connections
$ kill_close_wait_connections