I've been meaning to update the D2GS Packet Research post since for ever, as I dont think I changed much from the orginal list, posted around 2 weeks into the orginal 1st glance research.
I found a few random txt's and source codes on my comp and started refreshing/adding to the list -- I think theres almost 100 S>C packets documented now, altho descriptions are slim, to fit it all in one post.
It's been a year or 2 since I even thought about D2GS, so theres bound to be some typo's/error's/etc's in the list, so feel free to point them out and laugh, :p.
Theres still a fair few packets not listed, but as a starting/basepoint list, it should be alot better than it was(?).

I was also thinking, if I get the time/sudden will again, of adding a post with links to posts explaining how to carry out a number of common yet slightly complicated actions with in D2GS, such as, but not limited to "packet definition of how to; use a waypoint, use a teleport, trade/shop with town NPC,  how to etc the etc when you're etc, etc.", etc.
Feel free to add ideas on that!

I've also added somthing about C>S 0xFF packet, in the D2GS Packet Research C>S thread, if anyones interested.
I've known about this packet for some years after obtaining its packet ID, lengh and format, via brute forceing. I've only told 1-2 ppl about it and its format, so I would assume it's still very much secret/unknown.
I would be iterested to see/hear what peoples theorys are/what they find out about the values in the responce to this and/or the request its self :p
Basicly, connect to any closed D2GS, it doesn't matter if you have an invite from the d2gs/realm or not as you don't need to login/enter.
After connecting you will recv the tippical 0xAF packet, with the payload of the 0x01 byte to say data compressed, etc.
Now send;
[code]
FF 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[/code]
You will then recv an always uncomressed responce, like;
[code]
01 00 00 00 00 01 00 00 00 06 00 08 00 38 00 CA       .............8..
00 FF FF FF 7F FF FF FF 7F 00 C0 80 C5 00 20 47       .............. G
D6 87 13 00 00 BC 21 00 00 44 32 47 53 20 63 6F       ......!..D2GS co
6D 70 69 6C 65 64 20 61 74 20 31 34 3A 33 37 3A       mpiled at 14:37:
30 36 20 6F 6E 20 46 65 62 20 32 30 20 32 30 30       06 on Feb 20 200
37 20 52 45 4C 45 41 53 45 00 00 00 00 00 00 00       7 RELEASE.......
9C FC D5 06 0C 1A 99 6F 00 00 00 47 A8 B5 57 7C       .......o...G..W|
00 00 00 00 00 00 00 00 01 00 00 00 DB B3 57 7C       ..............W|
0C 21 00 00 00 00 00 00 00 00 00 00 79 23 96 6F       .!..........y#.o
0F 97 57 7C 64 24 96 6F E4 88 59 7C 00 00 00 00       ..W|d$.o..Y|....
00 00 00 00 10 27 00 00 E4 19 00 00 00 17 00 00       .....'..........
00 F4 01 00 00 1F 00 00 00 00 04 00 00 04 00 00       ................
00 00 00 00 00 01 00 00 00 00 00 00 00 01 00 00       ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00       ................
00 9A 02 00 00 01 00 12 00 01 00 02 00 01 00 00       ................
00 00 00 00 00 00 00 07 00 05 00 01 00 01 00 04       ................
00 00 00 00 00 01 00 01 00 03 00 03 00 00 00 14       ................
00 00 00 09 00 00 00 16 00 00 00 00 00 00 00 00       ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00       ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00       ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00       ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00       ................
00 00 00 00 00                                        .....
[/code]
Apart from the D2GS's uptime system structure, at offset 0x02, and the compile info string, you're guess is as good as mine on the other values-- some of them change every request, some of them remain constant, they could just be some random memory block, or mean somthing to the admins who would normaly use this packet(?).
I just spammed it back and forth once, sold some sojs in agame on the same server, and didn't notice anything move in releation, so never looked into any of those many many other dwords. Theres b ound to be a few easy ones, like number of open games on server, number of clients on server, etc. :)
Keep in mind i've not probed this in 1 to 2 years, but I litterly just tested it, and it still works, altho, the current D2GS is new'er, "D2GS cmpiled at 09:12:18 on May 28 2008 RELEASE".

Been looking for this packet for over a year now; a MH I used to use would list the number of games currently on the server, but I never tried to figure out how it was done. I'll look more into it when I get some free time.

cheers, mate.

Found it about 20 months ago. it's server system monitoring packet, nothing related to gameplay
has four subfunctions (FFFA, FFFB, FFFC, and FFFD;  FF01 is alias for FFFD or very similar to it)