well,

something wrong in my software, i wish I got to the point that I could find that one out..
I sent a sample max patch to the lanbox people in Rotterdam (www.lanbox.com), they had to fill in their header, ip and port, and it worked immediately with their ethernet box. No problem.
So I am positive that I'm sending proper utp out.

this limits it to two things:

A:

my header or ip settings are wrong. This is a documentation issue, has nothing to do with my software. I follow the specs, some of the advice I got (an tried) on this forum is different, especiialy the port and ip settings. I find the specs are not unambiguous. The header for an artnetdmx packet I use is this (list of char values in decimal, so shorts are split in hi and lo byte):
65 114 116 45 78 101 116 0
0 80
0 14
0 0
0 universe
lengthHi lengthLo

in the specs it says the bytes of the opcode are reversed (why would anyone do that ?), so I would be curious to see what the content of the 'opcode' field in your struct is.

B:

it is a hardware issue of some sort, faulty box (unlikely, true, but i start to doubt seriously) or some kind of ethernet incompatibilty I fail to understand.

ok, this is what happens with the switch:
1. ethernet switch on
2. arnet box on
3. plug in artnet box into switch: green light on switch comes on, no yellow light on artnet unit.
4. plug in mac into switch: green light on switch comes on, mac sees the network.
5. I send data: green light on switch for the artnet box dies. Nothing happens, leds go into chase mode.

my issues are:

- I will have to wait for at least an hour before I can try again: my experience is that if I just power the artnet box again, it will completly fail to respond to anything I send it. Only after a 'very cold' boot the switch (or the hub I used previously) will see the artnet box is there, I have never actually seen the artnet box with a yellow light on.
I don't know what couses this behaviour, it is not mentioned anywhere, and makes any sort of testing basically impossible. Why would any device behave in this way ?

- it is still not clear to me what the *exact* meaning of the yellow light is, Is it a light indicating the status of the network, like the green light next to ethernet port of my modem, which is always on, without blinking, OR is it a light indicating valid data traffic, like the activity lights on my hub and on my newly acquired switch ?
so: if it is not on, does that mean that no data whatsoever arrives, or does it mean that I send the wrong data ?


I am getting seriously annoyed at having to think about ethernet and about trivial headers, I want light !

I am going to give it another try (in an hour..) with an 'unreversed' opcode (i think i tried that already before), then I'm going to give up wasting my time on this thing and buy a lanbox.