Symptoms

Access to your virtual machine using VMware Remote Console (VMRC) fails with the error message "Connection Error".

Cause

There are two possible causes for the connection error:

(A) The decentralized firewall of your institution (institute / faculty / professorship) prevents communication to the networks of the virtualization environment.
(B) As of VMRC version 11.0, the default transfer protocol has been changed to the WebSocket port tcp/443. In previous versions, communication to the host systems was done via the MKS port tcp/902.

For security reasons, the WebSocket port for access from the campus networks is disabled on the host systems. Access via the VMRC is only possible via the MKS port tcp/902. Thus, a connection to the WebSocket port from the VMRC to the host systems is not possible.

Solution

(to A) To confirm missing rules in your institution's firewall as the cause of the problem, first connect to a VPN. More information about VPN can be found here.
If the VMRC connection from VPN works, the following rules must be added to the firewall by your institution's firewall administrator:

Zielnetze	Port
VMRC Proxy Server vmrc-enterprise-lzr.zih.tu-dresden.de (172.30.154.12) & vmrc-enterprise-tre.zih.tu-dresden.de (172.30.170.12)	tcp/443
Hostsysteme 172.30.154.0/24 172.30.170.0/24	tcp/902

(to B) Configure VMware Remote Console 11.x to use legacy connection mode so that the data transfer protocol is switched back to MKS. To do this, open the VMRC settings file* and add the following parameters:
```
pref.preferWebMKS = "FALSE"
pref.preferWebRemoteDevice = "FALSE"
```
*The VMRC settings file is located in the following location on your computer:
Windows:
```
 %APPDATA%\VMware\preferences.ini
```
MacOS (Standard installation):
```
 ~/Library/Preferences/VMware Remote Console/preferences
```
MacOS (App Store Installation):
```
~/Library/Containers/com.vmware.vmrc/Data/Library/Preferences/VMware Remote Console/preferences
```
Linux:
```
 ~/.vmware/preferences
```