Connecting to a modern Xserver with an old client

[Carsten Haitzler]

On Sat, 22 Jul 2023 20:47:03 +0000 (UTC) Michael K <vk2bea at yahoo.com> said:

> 
> To answer Grant's question. Yes, I had added the X ports but I've now turned
> off the firewall just to be sure. Here is the wireshark conversation.  I'm
> not knowledgeable enough to recognize the issue..
> 
> 1    0.000000000    192.168.1.16    192.168.1.1    TCP    60    6915 → 6001
> [SYN] Seq=0 Win=0 Len=0 MSS=1416
> 2    0.000165997    192.168.1.1    192.168.1.16    TCP    58    6001 → 6915
> [SYN, ACK] Seq=0 Ack=1 Win=64240 Len=0 MSS=1460
> 3    0.005196101    192.168.1.16    192.168.1.1    TCP    60    6915 → 6001
> [ACK] Seq=1 Ack=1 Win=1416 Len=0
> 4    0.008854195    192.168.1.16    192.168.1.1    X11    66    Initial
> connection request
> 5    0.008914324    192.168.1.1    192.168.1.16    TCP    54    6001 → 6915
> [ACK] Seq=1 Ack=13 Win=64228 Len=0
> 6    0.009029932    192.168.1.1    192.168.1.16    TCP    62    6001 → 6915
> [PSH, ACK] Seq=1 Ack=13 Win=64228 Len=8 [TCP segment of a reassembled PDU]
> 7    0.009086172    192.168.1.1    192.168.1.16    X11    110    Initial
> connection reply
> 8    0.009149782    192.168.1.1    192.168.1.16    TCP    54    6001 → 6915
> [FIN, ACK] Seq=65 Ack=13 Win=64228 Len=0
> 9    0.017057921    192.168.1.16    192.168.1.1    TCP    60    [TCP
> ZeroWindow] 6915 → 6001 [ACK] Seq=13 Ack=66 Win=0 Len=0
> 10    0.019632130    192.168.1.16    192.168.1.1    TCP    60    [TCP
> ZeroWindow] 6915 → 6001 [ACK] Seq=13 Ack=66 Win=0 Len=0
> 11    0.023341315    192.168.1.16    192.168.1.1    TCP    60    [TCP
> ZeroWindow] 6915 → 6001 [ACK] Seq=13 Ack=66 Win=0 Len=0
> 12    0.083569102    192.168.1.16    192.168.1.1    TCP    60    6915 → 6001
> [FIN, PSH, ACK] Seq=13 Ack=66 Win=0 Len=0
> 13    0.083647415    192.168.1.1    192.168.1.16    TCP    54    6001 → 6915
> [ACK] Seq=66 Ack=14 Win=64228 Len=0
> 
> Also, yes the X display is 1 on this server.

OK - looks like it's connecting and actually talking, so your next port of call
might be some x11 protocol analysis. xtrace. xscope are some of these.

I'm wondering if it's trying to create a colormapped window with a private
colormap assuming a pseudocolor display (or using a pseudocolor visual). given
an old enough app it may never have worked on truecolor displays.


-- 
------------- Codito, ergo sum - "I code, therefore I am" --------------
Carsten Haitzler - raster at rasterman.com