[Resolved] Finding unused port

[Drakla]

Hi all. I'm trying to detect if ports are unused on the server so I can set it up, do my stuff, then close it again - I'm wondering if this method using fsockopen is a really rubbish - I'm quite hoping for a right slap on this as it's just brutal door knocking - but I'd also welcome "Yeah, that's probably the way I'd do it" too.

Cheers.

function find_unused_socket()
{
	$port=9050;
	$portLimit=$port + 100;

$freePort=0;

while($port < $portLimit )
{
	$fp=@fsockopen('127.0.0.1', $port, $errno, $errstr, .005);

	if( $fp )
	{
		echo $errno.' ';			echo "$port in use";
		fclose($fp);
	}
	else
	{
		echo $errno.' ' ;			echo "$port free";
		$freePort=$port;
	}

	echo '<br>';			

	$port++;		
}

return $freePort;
}

[MarkR]

You should bind the socket with a port of 0, then the OS will automatically select an unused port, you can use getsockname to find out what port it's assigned.

I've no idea how you do this in PHP, that's what I do in C.

Mark

[Drakla]

Mark - you are an absolute star!

This is just a quick script I used to test it

<?php /* I've just been told that binding a socket to ZERO will automatically get me one assigned 
		And it's a winner!*/
$address='127.0.0.1';
$port=0;

$sock = socket_create(AF_INET, SOCK_STREAM, 0); 

// Bind the socket to an address/port 
socket_bind($sock, $address, $port) or die('Could not bind to address'); 

socket_getsockname ( $sock, $checkAddress, $checkPort );

echo "Port address $checkAddress<br>Port number $checkPort";	

socket_close($sock);
?>