MySQL over TCP results on CLOSE_WAIT state in PHP 5.3.8

Hi, I have a MySQL server A, a server B with PHP 5.3.8 and a server C with PHP 5.3.3. I'm connecting to the MySQL server on A via TCP from B and C using an internal network. Server B and C use the same PHP application. There are also same PHP scripts that get data from the database and then calculate up to 30 minutes. I close all database connection before doing the calculation to save connections (and ports) using: $thread_id = mysqli_thread_id( $this->handle ); mysqli_kill( $this->handle, $thread_id ); mysqli_close( $this->handle ); During a review on our servers I discovered that server B has a lot of network connection in the state "CLOSE_WAIT". Server C running the same PHP application has not. I see the difference that server B is using mysqlnd and server C not. serverB# netstat -an | grep 3306 tcp 1 0 10.8.0.58:47455 10.8.0.1:3306 CLOSE_WAIT serverA# cat firewall Feb 17 16:21:49 www kernel: [6587053.325075] SFW2-OUT-ERROR IN= OUT=tun0 SRC=10.8.0.1 DST=10.8.0.58 LEN=40 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=TCP SPT=3306 DPT=47455 WINDOW=0 RES=0x00 RST URGP=0 Does anybody have an idea why this happens? How can I avoid this or investigate in this? Is this a know issue?