On Fri, 2 Aug 2002, Brendan Moran wrote:

> For anyone who hasn't already sold their module, or intends to use
> something similar to this in the future, there's an easy solution to
> this problem:  send a PING to the server with a specific command in
> the body of the packet (which is usually not used in a PING) that
> tells the server to log that IP and MAC and use it to transmit
> whatever.  The chances of someone sending that specific packet
> erroneously are unlikely, especially if you use a strange data length
> such as 9 bytes, whereas the normal is 32.

UDP, TCP, ICMP, whatever -- still the same problem.  If you're going to
generate a packet out of the blue to send to a remote host, you have to
have, or have a way to determine, the MAC address to use.

On a local or switched network, you send an ARP request, get an ARP reply,
get the MAC from that reply, and send the packet with your target IP
address to that MAC address.  On a non-local network you send an ARP
request for the gateway, get the gateway's MAC from the ARP response, adn
send the packet with your target IP to the gateway's MAC address.

Siteplayer lacks ARP capability, which means you have to know the MAC
address to send to.  You can get this either from your received packet, or
you can know the MAC ahead of time.  Neither worked for me, though like I
said getting the MAC address from the request packet works fine.

Dale

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