This article covers how to diagnose and fix the most common Middleware issues, including Middleware showing Offline, service running but still Offline, periodic disconnects, and token mismatches. For installation and configuration, see Installing the Viz Flowics Middleware and Configuring the Viz Flowics Middleware.
For installation and configuration, please refer to Installing the Viz Flowics Middleware and Configuring the Viz Flowics Middleware.
How to check the Middleware status
Go to Settings in the top menu.
Select Middlewares.
Click the Monitoring tab.
The status shows as Online or Offline. You can also view the status of individual Middleware Sources from this tab (if you are not using NCS integrations).
By regularly monitoring the Middleware's status, you can ensure its smooth operation and promptly address any potential issues.
If your Middleware is showing Offline, start with the Quick checklist below.
Quick checklist — start here when status shows Offline
Is the Middleware service running on the local machine? (Check Windows Services or run
bin/flowics-middleware statuson Linux.)Does the token in
conf/middleware.propertiesmatch the token shown in Settings → Middlewares in the platform?Does the machine have outbound internet access on ports 80 and 443?
Is the Middleware module enabled on your company account?
Is the Project Running or Stopped?
Is the company plan active (not expired)?
Middleware shows Offline — step-by-step diagnosis
This is the most common Middleware issue. The platform showing "Offline" means Flowics cannot reach the Middleware service running on your computer. Work through these steps in order:
Step 1 — Confirm the Middleware service is actually running
On Windows:
Open Services (search "Services" in the Start menu).
Look for Flowics Middleware in the list and confirm the status is "Running."
If it is stopped, right-click → Start.
Alternatively, check if the standalone mode window is still open (bin/flowics-middleware.bat). If it was closed, the Middleware stopped.
On Linux:
Run
bin/flowics-middleware statusto check.If stopped, run
bin/flowics-middleware start.
Step 2 — Confirm the token in the config file is correct
The most common cause of "service running but still Offline" is a wrong or missing token in the local config file.
Navigate to the Middleware installation folder on your computer (e.g.
C:\Flowics\bin).Open the file
conf/middleware.propertiesin a text editor.Confirm the token value matches the Middleware token shown in Settings → Middlewares in the Flowics platform.
If the token is wrong or missing, paste the correct token, save the file, and restart the Middleware service.
Important: The token shown in Settings → Middlewares in the Flowics platform is fixed; it cannot be changed or regenerated. The most common cause of a token mismatch is a copy-paste error during installation: an extra space, a missing character, or an incomplete token in the middleware.properties file. Double-check the token in your local file, character by character, against the one shown on the platform. Even a single difference will cause the Middleware to show Offline.
Step 3 — Check firewall and network
The Middleware needs outbound internet access on ports 80 and 443 (HTTP/HTTPS). If your network has a firewall:
Allow outbound connections to all domains on ports 80 and 443.
This includes subdomains from social platforms (e.g.
video.twimg.com,pbs.twimg.com,facebook.com,instagram.com), If you use social data sources.Test by temporarily disabling the firewall; if the Middleware comes online, the firewall is blocking it.
Step 4 — Check the Middleware logs for errors
Logs are located in the logs/ folder inside your Middleware installation directory. Open the most recent log file and look for ERROR lines. Common errors you may see:
Address already in use: bind— port 9090 is taken by another process. See the port conflict section below.Authentication errors — the token is wrong, or the Middleware module is not enabled on your account.
Network errors — outbound connection is being blocked.
For MOS Gateway setups, you can also check error logs directly in the platform at Settings → MOS Config → [your config] → Status = ERROR.
The middleware service is running, but still shows Offline
If Windows Services shows the Middleware as "Running" but the platform still shows "Offline":
Check the token in
conf/middleware.properties— This is almost always the cause (see Step 2 above).Check if the Middleware module is enabled on your Flowics account. The Middleware module must be explicitly enabled on your company account. If it is not enabled, contact your Customer Success Manager or support.
Check if your trial has expired. An expired trial disables project activation, which prevents Middleware Sources from connecting. Check Settings → Company Usage for your plan status.
Try restarting the service, stop the service, wait 10 seconds, and start it again. Then wait 30 seconds before checking the platform status.
Middleware disconnects periodically and requires a restart
If the Middleware connects successfully but goes offline every day or two and requires a manual restart:
Check the Middleware logs for the time of each disconnect, look for ERROR entries around the time it goes offline. This will indicate whether it is a network drop, a memory issue, or a data source error.
Check your network connection stability. An intermittent internet connection on the Middleware computer will cause periodic disconnects. The Middleware will attempt to reconnect automatically, but may require a restart if the connection is down for too long.
Check for Windows Update restarts; if the Middleware is running in standalone mode (not as a Windows Service), a system restart will stop it. Install the Middleware as a Windows Service so it starts automatically at boot:
As an administrator, run
bin/flowics-middleware-install-service.bat.Confirm it appears in the Windows Services console set to start automatically.
Check data source load. If the Middleware is handling very high-frequency data sources or large volumes of media downloads, it may run out of resources. Review the sources configured and reduce polling frequency if possible.
"Address already in use: bind" error
This error means that port 9090 is already in use on your machine. This happens when:
You are running the Middleware in both standalone and service mode simultaneously.
Another application is using port 9090.
To fix:
If running in both modes, stop one of them.
To change the port the Middleware uses:
Open
conf/middleware.conf.Find the line
wrapper.app.parameter.2=9090.Change
9090to an available port (e.g.9091).Restart the Middleware.
If running multiple Middleware instances on the same machine, each instance must use a different port number.
Network share write error (Windows Service mode)
If the Middleware service cannot write to a mapped network drive (e.g. Z:\), it is because the Windows Service runs under a local system account that does not have access to network mappings created by your user account.
To fix this, ensure the network drive is:
Mapped at Windows startup (not just when you log in).
Accessible to the local account that runs the Middleware service.
See Microsoft's documentation on service logon accounts or the Middleware installation guide for specific steps.
Java / JRE issues on installation
The Middleware requires Java Runtime Environment (JRE) 21. If the Middleware fails to start after installation:
Confirm JRE 21 is installed — run
java -versionin a command prompt. The output should show version 21.Confirm the Java
binfolder is in your system PATH variable:Go to Control Panel → System → Advanced System Settings → Environment Variables.
Edit the Path system variable and confirm it includes the path to Java's bin folder (e.g.
C:\Program Files\Java\jre21\bin).If it is missing, add it to the top of the list and restart the computer.
If the Middleware still does not start, check the
logs/folder for the specific Java error.
Middleware module not enabled / plan expired
If you receive an error indicating the Middleware module is not active:
The Middleware module must be enabled on your Flowics company account. It is not included in all plans.
If your trial has expired, projects cannot be activated, which prevents Middleware Sources from connecting even if the service is running.
Contact your Customer Success Manager to confirm your plan includes the Middleware module and that your account is active.
Monitoring during version upgrades
When upgrading the Middleware, you can run two versions simultaneously using the same configuration token — one on the current server and one on a new server. This lets you test the new version without disrupting the existing setup.
Note that both instances will attempt to write to the same Shared Folder Path and to the same database (if configured). To avoid conflicts:
Run the new instance on a separate server.
Use a separate database for the new instance if you use database integration.
A version selector in the Monitoring tab lets you choose which Middleware version to observe.
When to contact support
Contact the support team if:
You have completed all steps above, and the Middleware is still showing Offline.
The logs show an error code not described in this article.
The Middleware module appears to be missing from your account.
When contacting support, include: your company name, the Middleware version, the error lines from the logs, and a screenshot of the Monitoring tab showing the Offline status.