# Remote Control - Knowledge base

## HTML 5 Viewer - Remote Connection Error!

### Problem

You are trying to establish remote connection using HTML 5 Viewer and you get the message **"HTML 5 Viewer remote connection error"**.

### Cause

This could be due to one the following reasons:

- [Unable to start remote control gateway](https://www.manageengine.com/products/desktop-central/html-5-viewer-remote-connection-error.html#rdsGatewayNotStarted)
- [Unable to start web socket Server, since the port is already in use](https://www.manageengine.com/products/desktop-central/html-5-viewer-remote-connection-error.html#wsPortInUse)
- [Web socket port has been blocked by the firewall](https://www.manageengine.com/products/desktop-central/html-5-viewer-remote-connection-error.html#wsPortBlocked)

### Resolution

### Unable to start remote control gateway

The ports that you have configured for remote control gateway is being used by some other process. You will have to either kill the process that is using the gateway ports or modify the ports that have been configured for remote control gateway. Follow the steps mentioned below to modify the port number:

1. On the Endpoint Central web console, click **Tools**
2. Select **Remote Control**
3. Choose **Settings**
4. Under **Port settings**, modify the gateway port numbers
5. Click **Save** to store the changes.

You can now retry to establish remote connection.

### Unable to start web socket Server, since the port is already in use

You can establish remote connection using Java Viewer or ActiveX, even if the specified ports are blocked/used. If you want to use HTML 5 Viewer, follow the steps mentioned in this section.

The ports that you have configured for HTML 5 Viewer are being used by some other process. You will have to either kill the process that is using the gateway ports or modify the ports that have been configured for remote control gateway. Follow the steps mentioned below to modify the port number:

1. On the Endpoint Central web console, click **Tools**
2. Select **Remote Control**
3. Choose **Settings**
4. Under **Port settings**, modify the HTML 5 Viewer port numbers. You can modify either HTTP or HTTPS port based on your requirement.
5. Click **Save** to store the changes.

You can now retry to establish remote connection.

### Web socket port has been blocked by the firewall

The ports that you have configured for remote control (HTML 5 Viewer) are being blocked in the firewall on the computer where the Endpoint Central server is installed. You will have to either modify the firewall restrictions or disable the Windows firewall to allow all inbound/outbound connections.

You can view the ports that are configured by navigating to the following location:

1. On the Endpoint Central web console, click **Tools**
2. Select **Remote Control**
3. Choose **Settings**
4. Under **Port settings**, you can view the ports that are configured for HTML 5 Viewer.

You can now retry to establish remote connection.

If you still have problems in establishing remote connection, ensure that the following specifications are met:

1. The ports that you have configured for HTML 5 Viewer (HTTP/HTTPS) should be reachable from the viewer machine.
2. The gateway port should be reachable from the agent machine.
3. If you are trying to establish remote connection with a Mac computer, then Java plugin should be installed on it and non-SSL gateway port should be reachable from the agent machine.

If the problem still persists, then you can contact Endpoint Central support.

**Applies to:** Remote Desktop Management, Troubleshoot Remote Desktop, Remote Desktop Connection Problems

**Keywords:** Remote Desktop, Manage Remote Computers, Troubleshoot Remote Machines

## Other KB articles

- [Agent Installation](https://www.manageengine.com/products/desktop-central/knowledge-base.html#agent-installation)
- [Configurations](https://www.manageengine.com/products/desktop-central/knowledge-base.html#windows-configurations)
- [Inventory Management](https://www.manageengine.com/products/desktop-central/knowledge-base.html#inventory-management)
- [Patch Management](https://www.manageengine.com/products/desktop-central/knowledge-base.html#patch-management)
- [Software Distribution](https://www.manageengine.com/products/desktop-central/knowledge-base.html#software-distribution)
- [Service Pack Installation](https://www.manageengine.com/products/desktop-central/knowledge-base.html#service-pack-installation)
- [Desktop Sharing](https://www.manageengine.com/products/desktop-central/knowledge-base.html#remote-desktop-sharing)
- [Active Directory Reports](https://www.manageengine.com/products/desktop-central/knowledge-base.html#active-directory-reports)
- [User Logon Reports](https://www.manageengine.com/products/desktop-central/knowledge-base.html#user-logon-reports)
- [Endpoint Central SP Upgrade](https://www.manageengine.com/products/desktop-central/knowledge-base.html#service-pack-upgrade)
- [Miscellaneous](https://www.manageengine.com/products/desktop-central/knowledge-base.html#miscellaneous)
- [» More](https://www.manageengine.com/products/desktop-central/knowledge-base.html)

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