primate:
What will probably happen is that we end up with everyone using all 00-00-00-00-00-00 as their MAC. I wonder if it might be an issue if you have multiple devices with the same MAC address on the same subnet though.
'Official' Ethernet shield comes with a sticker with an unique MAC written. It starts with 90-A2-DA-
The problem with multiple Arduinos is the same hostname "WIZnet", but it can be changed in the Ethernet library (Dhcp.h).
primate:
Also, does the Ethernet shield have existing libraries for DNS lookup and all that?
Yeah. I'm usign Arduino 1.0-beta1, which comes with DNS and DHCP support.
primate:
Finally, what's the bottleneck in this system? Ethernet is really fast so why would sending a 50KB picture take 30 seconds?.
Getting an IP (~4 seconds), reading each byte from the SD (~40 microseconds each: 6 s), SMTP traffic and load.... don't know exactly.
PaulS:
Besides, this thread started with sending the picture using a cell phone module.
? O_o
Sairam:
I am aware of the fact that it is possible to send emails to the SMTP server using the arduino ethernet shield. I want to send picture attachments along with the mail.