I have a Raspberry Pi set up as an access point using hostapd and dnsmasq I've got an Android tablet connected and a Samsung wireless printer.
I have iptables running on the Raspberry Pi with strict rules allowing only certain types of traffic. iptables is set to drop all traffic on the FORWARD chain (I did enable IPv4 Forwarding in the kernel, however I'm unsure if it persisted across reboots).
If I restrict the firewall rules so that it only allows incoming and outgoing SSH traffic (to allow me to manage the Raspberry Pi) the Samsung Print App still can find, connect to and print to the printer.
Using tshark I managed to find that the printer uses the Raw TCP/IP Printing Protocol, SSDP and mDNS. So unless I'm overlooking something (which I must be) I cannot see how the tablet and printer are communicating.
Any ideas on what could be going on?