PHP Udp socket close not freeing system resources

I am using the following piece of code in a php script to process incoming data over http and forward it to another module and waits for the response. It then closes the socket.

$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($sock,$host,$port) or die("");
if (!socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1)) {  
echo socket_strerror(socket_last_error($sock));
exit;
}
$arrOpt = array('l_onoff' => 1, 'l_linger' => 1);
socket_set_block($sock);
socket_set_option($sock, SOL_SOCKET, SO_LINGER, $arrOpt);
$address = gethostbyname($host);

$msg = $url;
$len = strlen($msg);
socket_sendto($sock, $msg, $len, 0, $remotehost, $remoteport) ;
socket_recvfrom($sock, $buff, 1000, 0, $host, $newport);
socket_close($sock);

The problem faced is that the response is received correctly and the socket_close error is also returning a success(output of socket_last_error). But after that if I do a netstat I see the port being in used and the process (output of /proc/pid/status) is in sleep state. This behavior is random in nature and I am using PHP version 5.3.8 on a Amazon EC2 cloud.

Solved

its about TIME_WAIT ... to free the socket

in Linux run # /proc/sys/net/ipv4/tcp_fin_timeout to find out .... (default 60 sec)

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