"pre-shared-key" extension in ServerHello

[cinqita]

Hello!
First, many thanks for the great article. It's absolutely the best thing about https in the whole international segment of internet. I reproduced every steps in tls 1.3 archieve. So, I bought domain, static IP, SSL-certificate, my client side was Mozilla Firefox and after several weeks I've done it. I've written a C-program (Server) which sends html pages in response to Mozilla GET-requests.

But I have a question about session ticket. I sent "Server New Session Ticket 2" from the tls 1.3 archieve, Mozilla accepted this ticket. When I start a new connection, Mozilla sends this ticket in the end of ClientHello to my server and waiting for the response. But I don't understand what I should send back in my ServerHello.

Dumping the last 207 bytes Client Hello (pre-shared-key extension):

00160  .. .. .. .. .. .. .. ..  .. 00 29 00 cb 00 a6 00  |.......@..).....|
00170  a0 01 06 09 11 16 19 21  26 29 31 36 39 41 46 49  |.......!&)169AFI|
00180  51 03 06 09 13 16 19 23  26 29 33 36 39 43 46 49  |Q......#&)369CFI|
00190  53 f7 00 29 ec f2 c4 a4  41 fc 30 17 2e 9f 7c a8  |S..)....A.0...|.|
001a0  af 4f 69 19 7b 80 48 84  c2 df 76 0c f4 be 7b 8b  |.Oi.{.H...v...{.|
001b0  6d fb 71 73 e9 90 52 ef  4b 50 18 2f c0 74 43 ed  |m.qs..R.KP./.tC.|
001c0  10 a9 f5 07 05 67 05 3a  2a e8 f2 18 17 9c 11 f1  |.....g.:*.......|
001d0  f1 3e c9 d1 85 7f 8e 01  b4 99 ff 24 82 c6 2a f7  |.>.........$..*.|
001e0  4e 1c 86 a9 fc ca d9 84  c9 ab ec 40 de 80 03 a8  |N..........@....|
001f0  16 4f fc a6 8f 92 5f 25  f3 be 18 41 66 17 2b fb  |.O...._%...Af.+.|
00200  ef 66 4b 0a 5d 6f 94 cc  ed c7 c2 2f 64 29 a3 18  |.fK.]o...../d...|
00210  5f 09 08 4a ca 00 21 20  88 35 66 99 ec 06 18 0e  |...J..! .5f.....|
00220  b7 11 26 de b2 9c 48 81  90 78 e8 31 95 29 da 1b  |..&...H..x.1.)..|
00230  da 22 5e 1b 28 0f 0d b1                           |."^.(...|

I understand that:

• bytes 00 29 00 cb 00 a6 00 a0; 00 29 - pre-shared-key extension, 00 cb - length of extension, 00 a6 - length of session ticket and 4 strange bytes 09 08 4a ca from position 211-214, 00 a0 - length of session ticket
• 01 06 ... 18 5f - is session ticket

I don't understand:

• bytes 09 08 4a ca, extension 00 21 after these 4 bytes, okay 20 is a length
• the meaning and calculation of the last 32 bytes 88 35 ... 0d b1

I've read RFC-8446, 4.2.11, but only found that:

selected_identity: The server's chosen identity expressed as a
(0-based) index into the identities in the client's list.

It doesn't help me to understand and to write ServerHello.

Can you help me, please? Two questions

1. What should I write in pre-shared-key extension in my ServerHello to make Mozilla accept my ServerHello message? After accepting Mozilla should send me encrypted Application data with GET-request
2. The meaning and calculation of 09 08 4a ca, 00 21 and 88 35 ... 0d b1