Can I communicate with user of my open WiFi router?

I have a wireless router which I keep open. I have plenty of bandwidth with my ISP so I don't mind allowing iTouches/iPhones and local computers to use my connection.

I have noticed a couple regulars though who use my connection every day. I have their client name and their MAC addresses. Is there anyway for me to communicate with these users? Like if they live next door, it would be nice to see if I could get them to pitch in towards my ISP bill.

Hey first you need to know their ip address. See if the router has their IP entry like checking in the ARP cache of the router. Probably if you have option to do a MAC filtering in the router, you can put these MAC address of the station which you dont want them to use the bandwidth and deny their access.

If your router is dhcp..check the logs of the router and see how many ips it had released and eliminating the known ip..you should be able to trace all others.

Ya, I can see their ip addresses too. I know i can ban them from using my router, but I'd rather just try to see if it's a local neighbour who I could get to pitch in for my ISP bill, so I want to communicate with them.

I tried using NET SEND command (used to work Windows NT back in the day). Obviously, I'm no expert though, so I'm asking here.