Shutting down a socket in PHP - php

Question

I created a cache server and client in php, no need to ask why, just for fun. The implementation works, but a problem occures every time when:
Server starts
Client connects
Server stores data
Client disconnects
When I stop the running server process, after a client disconnects and trying to restart the server, the socket_bind throws an error, that the address is already in use. The client always closes connection after the data has been sent or recieved and when I check if the port is in use via sudo netstat, the port is not listed. The server looks like this:
public function run()
{
$this->socket = $this->ioHandler->createServerSocket();
while ($this->running) {
while ($connection = #socket_accept($this->socket)) {
socket_set_nonblock($connection);
$this->maintainer->maintainBucket($this->bucket);
$this->maintainer->checkBackup(time(), $this->bucket);
try {
$dataString = $this->ioHandler->readFromSocket($connection);
$data = unserialize($dataString);
($this->actionHandler)($data, $this->bucket, $this->ioHandler, $connection);
} catch (Exception $ex) {
$this->ioHandler->writeToSocket($connection, self::NACK);
$this->ioHandler->closeSocket($connection);
}
}
}
}
I think the problem might be that the server shuts down via a simple ctrl+c or a start-stop-daemon --stop --pidfile and the socket is still open and there might be some automatized service that cleans up dead sockets. How can I properly shut down the server? Can I somehow terminate the process by sending an input via STDIN to kill the server socket? Or am I wrong on the issue? The full code is available on github: https://github.com/dude920228/php-cache

Answer 1

Perhaps it's related to TIME_WAIT state. Long story short - socket_close() may close the socket, but there still may be data to send. Until the data is sent, the port will not be available.
More info is:
here
here
and here