RustDesk Server on QNAP – IPv6 / IPv4 ZeroTier - Failed to connect to relay server

1 Environment

Docker 20.x and QTS 5.x on a QNAP NAS.
QNAP NAS 上运行 QTS 5.x 与 Docker 20.x。

No public IPv4, only global IPv6 and a ZeroTier /24 overlay.
没有公网 IPv4，仅有全球单播 IPv6 和一段 ZeroTier /24 虚拟网段。

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2 Key files & directory

/share/Container/rustdesk-data/ holds keys, DB and lists.
密钥、数据库与黑名单都放在 /share/Container/rustdesk-data/。

id_ed25519            # PEM private key (600)
id_ed25519.pub        # public key (644)
db_v2.sqlite3         # auto-generated
blacklist.txt / blocklist.txt

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3 Containers (1.1.9 tag)

Relay (HBBR) listens on 21117 over all NICs.
中继 HBBR 在所有网卡上监听 21117 端口。

docker run -d --name hbbr --network host \
  -v /share/Container/rustdesk-data:/root \
  rustdesk/rustdesk-server:1.1.9 \
  hbbr --port 21117

Rendezvous (HBBS) advertises IPv6 + ZeroTier addresses.
HBBS 同时广播 IPv6 与 ZeroTier 地址。

docker run -d --name hbbs --network host \
  -v /share/Container/rustdesk-data:/root \
  -e ALWAYS_USE_RELAY=Y \
  rustdesk/rustdesk-server:1.1.9 \
  hbbs \
  --relay-servers "[2001:db8::1]:21117,<ZeroTier IPv4>:21117"

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4 Firewall rules

UDP 21116 and TCP 21115-21117 are allowed on IPv4/IPv6.
在 IPv6 与 ZeroTier 接口上放行 UDP 21116 与 TCP 21115-21117。

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5 Validation logs

HBBS shows it is listening and broadcasting both addresses.
HBBS 日志显示正在监听并广播两类地址。

Listening on tcp/udp :21116
relay-servers=["[2001:db8::1]:21117", "172.26.104.186:21117"]

HBBR receives relay requests from two different networks.
HBBR 收到了来自两张网络的中继请求。

New relay request … from [2001:db8::2]:4371
New relay request … from [::ffff:172.26.1.139]:37819

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6 Current status

Handshake and relay requests arrive, but no “Established relay” ever appears.
握手与中继请求均已到达，但始终未出现 “Established relay” 日志。

Result: clients still report “Failed to connect to relay server”; root cause undetermined.
结果：客户端依旧提示 “Failed to connect to relay server”，原因尚未查明。

Start by reproducing the issue with the listed Docker commands for hbbs and hbbr, then inspect their relay-request and connection logs across the IPv6 and ZeroTier interfaces. Compare the advertised addresses, allowed ports, and incoming requests; done means identifying the cause of the missing “Established relay” event and confirming a successful relay connection.