And why do you think it's PHP related?

The reason why is if you take a normal DHCP server you can typically listen on multiple interfaces.  If one wanted to know what interface is receiving the data you would think to bind on the interfaces IP address.  But since you cannot see that type of packet binding to an IP like that you must bind to 0 or 0.0.0.0 which doesn't help with knowing what interface recieved the data since the data does not contain information about interface mac/ip destination from the client. I'm not positive if this is a PHP issue or not but I believe you can do it in C/C++ and that you should be able to do it with PHP.  A work around I'm experimenting with  goes as:

<?php
$interface_ip = "10.66.66.1";
$interface_port = 67;
//listens for dhcp requests
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
//you must bind to 0.0.0.0 to actually see anything
socket_bind($socket, 0, 67);
while(1)
{
  if($src = @socket_recvfrom($socket, $data, 9999, 0, $interface_ip, $interface_port))
  {
    echo "data!\n";
  }
}
?>

Ignore my previous workaround example, it did not work as expected.

I believe in C/C++ you can specify hardware addresses to listen on - specifically either a MAC address/an interface name (eth0 in linux).  

After doing some tests in C it seems that if you listen on an ip (i.e. 192.168.0.1) and you will not see that type of packet but if you listen on 0.0.0.0 or INADDR_ANY you can see it.

The way it seems this should work (I easily could be completely off 
base) is:

socket_bind could be defined as:

bool socket_bind ( resource $socket, string $address [, int $port [, 
string $mac or $iface ]] )

My first message had a working example but here it is again with more 
information.

The purpose is to see DHCP requests from a DHCP Client.  So use a DHCP 
Client to get an IP address on a system thats on the same network that 
this script is running on. 

This first example WON'T see the packets:
<?php
$ip = "ENTER YOUR IP ADDRESS HERE"; //example: 192.168.0.100
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($socket, $ip, 67);
while(1)
{
  if($src = @socket_recv($socket, $data, 9999, 0)) { echo "data!\n"; }
}
?>

This second example WILL see the packets:
<?php
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($socket, 0, 67);
while(1)
{
  if($src = @socket_recv($socket, $data, 9999, 0)) { echo "data!\n"; }
}
?>


This reference might give you a better idea of what I'm talking about:
http://en.wikipedia.org/wiki/Dhcp#DHCP_discovery

"A non-authoritative server simply ignores the request, leading to an implementation dependent time out for the client to give up on the request and ask for a new IP."

Isn't that exactly what is happening here?

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

Hy! I solved the problem:

<?php
$bc_socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); // for broadcast packets
$if_socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); // for answer packets

socket_bind($bc_socket, "255.255.255.255", 67); // listen to discover pcks.
socket_bind($if_socket, "10.0.0.1", 67); // target interface address

socket_set_option($bc_socket, SOL_SOCKET, SO_BROADCAST, 1);
socket_set_option($bc_socket, SOL_SOCKET, SO_REUSEADDR, 1);
socket_set_option($bc_socket, SOL_SOCKET, SO_DEBUG, 0);

socket_set_option($if_socket, SOL_SOCKET, SO_BROADCAST, 1);
socket_set_option($if_socket, SOL_SOCKET, SO_REUSEADDR, 1);
socket_set_option($if_socket, SOL_SOCKET, SO_DEBUG, 0);

while(1)
{
  if($src = @socket_recv($bc_socket, $data, 9999, 0))
  {
    echo "data!\n";
    $senddata = "....";
 	socket_sendto($if_socket, $senddata, strlen($senddata),0, "255.255.255.255", 68);
  }
}


?>

i'm running into the same problem to receive DHCP packets via PHP8.1 ... all the here mentioned codes arnt working now, maybe someone can confirm the behavior or give me a new hint to solve this problem.

regards, volker.