---
title: "RustDesk Pro Fix: “Failed to connect via relay server”"
description: "### Applies to - Synology NAS running **DSM 7.1.1** - Docker / Container Manager - **RustDesk Server Pro** - `hbbs` (ID / rendezvous server) - `hbbr` (relay server) --- ![](https://winsale.net/wp-content/uploads/2025/12/rustdeskKB.avif) ## Summary If RustDesk clients intermittently fail with **“Failed to…"
url: "https://winsale.net/docs/rustdesk-pro-fix-failed-to-connect-via-relay-server/"
updated: "2025-12-12"
category: Software Resolutions
tags:
  - docker
  - relay
  - rustdesk
---

# RustDesk Pro Fix: “Failed to connect via relay server”

### Applies to

- Synology NAS running **DSM 7.1.1**
- Docker / Container Manager
- **RustDesk Server Pro**
- `hbbs` (ID / rendezvous server)
- `hbbr` (relay server)

---

![](https://winsale.net/wp-content/uploads/2025/12/rustdeskKB.avif)

## Summary

If RustDesk clients intermittently fail with **“Failed to connect via relay server”**, even though ports are open and some connections work, the most common cause is that **hbbs is advertising the wrong relay address**.

On Synology DSM, this often happens because the relay server address is hard-coded at container startup and cannot be changed after the container is created.

---

## Symptoms

You may observe one or more of the following:

- Clients show **“Failed to connect via relay server”**
- Some devices connect successfully, others never do
- New installs behave the same as existing ones
- Direct connections sometimes work, relay connections fail
- Relay port appears open when tested externally

---

## Root Cause

`hbbs` is advertising the relay server as:

```
127.0.0.1:21117
```

This causes external clients to attempt relay connections to **their own local machine**, which always fails.

On DSM 7.1.1:

- The Docker UI does **not** allow editing the container command after creation
- Environment variables **do not override** the relay server
- The RustDesk Pro web UI does **not override** the container startup arguments

---

## Resolution

You must **recreate the `hbbs` container** with the correct relay server specified at startup.

---

## Step-by-Step Resolution

### Step 1 — Verify relay port is reachable externally

From a remote Windows PC:

```
Test-NetConnection yourhost.example.com -Port 21117
```

Expected result:

```
TcpTestSucceeded : True
```

If this fails, fix router port forwarding and DSM firewall rules before continuing.

---

### Step 2 — Check what relay server `hbbs` is advertising

SSH into the NAS and run:

```
sudo docker logs hbbs --tail 200 | grep -i relay-servers
```

#### Correct

```
relay-servers=["yourhost.example.com:21117"]
```

#### Incorrect

```
relay-servers=["127.0.0.1:21117"]
```

If you see `127.0.0.1`, continue to Step 3.

---

### Step 3 — Recreate `hbbs` with the correct relay server

> ⚠️ Do **not** delete volumes or data.

#### 3.1 Stop and remove the existing `hbbs` container

```
sudo docker stop hbbs
sudo docker rm hbbs
```

---

#### 3.2 Recreate `hbbs` with the relay server specified

Use the same volume path you previously used for RustDesk data.

```
sudo docker run -d 
  --name hbbs 
  --network host 
  --restart unless-stopped 
  -v /path/on/nas/rustdesk:/root 
  rustdesk/rustdesk-server-pro:latest 
  hbbs --relay-servers yourhost.example.com:21117
```

**Important**

- Keep `--network host`
- Do **not** use `https://`
- Use your public hostname or public IP

---

#### 3.3 Restart `hbbr`

```
sudo docker restart hbbr
```

---

### Step 4 — Verify the fix

```
sudo docker logs hbbs --tail 80 | grep -i relay-servers
```

Expected:

```
relay-servers=["yourhost.example.com:21117"]
```

At this point, relay connections should begin working immediately.

---

## Step 5 — Verify RustDesk Pro license status

License issues can cause unstable or partial functionality.

```
sudo docker logs hbbs --tail 200 | egrep -i "license|License"
```

Expected:

```
License OK
```

If you see messages indicating the license is in use on another machine, complete the license migration process in the RustDesk Pro portal and restart the containers.

---

## Step 6 — Confirm relay server health

```
sudo docker logs hbbr --tail 80
```

You should see:

- Listening on `tcp :21117`

Optional socket check:

```
sudo ss -tulpen | egrep '21115|21116|21117|21114'
```

---

## Client Configuration Notes

### Custom Server Settings

- **Host:** `yourhost.example.com`
- **Key:** Your RustDesk public key
- **API:** Use `http://` or `https://` **only if your API endpoint supports it**

### API Scheme Test

```
curl -I http://yourhost.example.com:21114
curl -kI https://yourhost.example.com:21114
```

Use the scheme that returns a valid response.

---

## Common Mistakes

❌ Setting relay server via environment variables
❌ Expecting the Pro web UI to override container startup
❌ Using `127.0.0.1` or LAN IP as relay server
❌ Adding `https://` to relay server field
❌ Editing an existing container instead of recreating it

---

## Recommended Best Practice

Use **docker-compose** for repeatable deployments:

```
services:
  hbbs:
    image: rustdesk/rustdesk-server-pro:latest
    container_name: hbbs
    network_mode: host
    command: hbbs --relay-servers yourhost.example.com:21117
    volumes:
      - /path/on/nas/rustdesk:/root
    restart: unless-stopped

  hbbr:
    image: rustdesk/rustdesk-server-pro:latest
    container_name: hbbr
    network_mode: host
    command: hbbr
    volumes:
      - /path/on/nas/rustdesk:/root
    restart: unless-stopped
```

---

## Verification Checklist

✔ Relay port reachable externally
✔ `hbbs` advertises public relay address
✔ License status OK
✔ Containers running in host mode
✔ Relay connections succeed consistently

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