Can't connect to WebUI via Ethernet cable or WiFi after using for 2 months

[oshyshko]

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Can't access WebUI from a machine via ethernet cable or when in the same WiFi network.
The 47990 port is open and can be seen as such from another machine, but connection closed when accessed.

How to fix it? Where to look?

See more details below.

2 machines:

• macos client - 192.168.2.1
• windows server (sunshine - v2025.628.4510, v2025.829.135256) - 192.168.2.2

Ethernet cable between (also tried to do via WiFi -- same result).
mac (192.168.2.1) shares internet to windows (192.168.2.2).

Firewalls off on both machines.
On windows, just in case, added inbound+outbound rules in Defender for sunshine.exe: all ports.

IPv4 only on both machines.

Can ping each other.
Can run python -m http.server 8080 and access from another machine.

Can open http://localhost:47990 on windows (192.168.2.2).
Can't open http://192.168.2.2:47990/ from mac (192.168.2.1) -- browser shows "can't connect".

Sunshine fresh install + set password.
All settings default, including "Origin WebUI Allow" defaulting to "Only those in LAN may access Web UI".

Running netstat on windows shows that 0.0.0.0:47990 is being listened. PID 8944 below is "Sunshine.exe".

c:\> netstat -ano -p tcp

Active Connections

  Proto  Local Address          Foreign Address        State           PID
...
  TCP    0.0.0.0:47984          0.0.0.0:0              LISTENING       8944
  TCP    0.0.0.0:47989          0.0.0.0:0              LISTENING       8944
  TCP    0.0.0.0:47990          0.0.0.0:0              LISTENING       8944
  TCP    0.0.0.0:48010          0.0.0.0:0              LISTENING       8944
...

Running nmap from mac (192.168.2.1) shows:

 $ sudo nmap -sS -p 47000-48050 192.168.2.2
Password:
Starting Nmap 7.98 ( https://nmap.org ) at 2025-09-11 23:25 -0500
Nmap scan report for 192.168.2.2
Host is up (0.065s latency).
Not shown: 1047 filtered tcp ports (no-response)
PORT      STATE SERVICE
47984/tcp open  unknown
47989/tcp open  unknown
47990/tcp open  unknown
48010/tcp open  unknown
MAC Address: ...

Nmap done: 1 IP address (1 host up) scanned in 164.61 seconds

Notice: mac can see that port 47990 on windows is being listened.

Running nc 192.168.2.2 47990 from mac + recording traffic using Wireshark gives this in console (connection closed):

$ nc 192.168.2.2 47990
GET /
$

Wireshark dump for the above nmap command, with filter tcp.port == 47990:

No.     Time           Source                Destination           Protocol Length Info

     13 10.645436      192.168.2.1           192.168.2.2           TCP      78     50404 → 47990 [SYN, ECE, CWR] Seq=0 Win=65535 Len=0 MSS=1460 WS=64 TSval=1600475896 TSecr=0 SACK_PERM
     14 10.646536      192.168.2.2           192.168.2.1           TCP      74     47990 → 50404 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=256 SACK_PERM TSval=5793920 TSecr=1600475896
     15 10.646896      192.168.2.1           192.168.2.2           TCP      66     50404 → 47990 [ACK] Seq=1 Ack=1 Win=131776 Len=0 TSval=1600475898 TSecr=5793920
     19 12.683164      192.168.2.1           192.168.2.2           TCP      72     50404 → 47990 [PSH, ACK] Seq=1 Ack=1 Win=131776 Len=6 TSval=1600477934 TSecr=5793920

Frame 19: 72 bytes on wire (576 bits), 72 bytes captured (576 bits) on interface en7, id 0
Ethernet II, Src: 72:8c:f2:0b:d6:64 (72:8c:f2:0b:d6:64), Dst: HCElectronic_3:9f:e8 (c8:ff:bf:03:9f:e8)
Internet Protocol Version 4, Src: 192.168.2.1, Dst: 192.168.2.2
Transmission Control Protocol, Src Port: 50404, Dst Port: 47990, Seq: 1, Ack: 1, Len: 6
Data (6 bytes)

0000  47 45 54 20 2f 0a                                 GET /.

No.     Time           Source                Destination           Protocol Length Info
     20 12.684416      192.168.2.2           192.168.2.1           TCP      66     47990 → 50404 [FIN, ACK] Seq=1 Ack=7 Win=65280 Len=0 TSval=5795959 TSecr=1600477934
     21 12.684787      192.168.2.1           192.168.2.2           TCP      66     50404 → 47990 [ACK] Seq=7 Ack=2 Win=131776 Len=0 TSval=1600477936 TSecr=5795959
     22 12.684966      192.168.2.1           192.168.2.2           TCP      66     50404 → 47990 [FIN, ACK] Seq=7 Ack=2 Win=131776 Len=0 TSval=1600477936 TSecr=5795959
     23 12.685892      192.168.2.2           192.168.2.1           TCP      66     47990 → 50404 [ACK] Seq=2 Ack=8 Win=65280 Len=0 TSval=5795960 TSecr=1600477936

[oshyshko]

Solved.
Settings -> Privacy & Security -> Local Network.
Then set tick next to Moonlight.