VMware Horizon Client Connection Failed Timeout Was Reached

The error VMware Horizon client connection failed timeout was reached is generally known to occur in a client-server environment wherein the client system running on Horizon fails to establish a proper physical connection with the VMware server within a specific timeframe. This issue can prevent users from accessing network resources or applications, leading to workflow disruptions. In this article, we aim to find out the possible causes leading to the error and steps that can be undertaken to resolve the issue quickly and effectively.

VMware Horizon Client Connection Failed Timeout Was Reached

What is a  VMware Horizon Client?

VMware Horizon is a group or family of technical tools that can help us access systems, applications, and resources virtually in a client-server environment. Developed by VMware, Horizon Client is a software application that acts as a gateway or interface to connect with virtual desktops and applications installed or hosted on VMware Horizon Servers.

This software can help us connect to a particular system or device or their resources anytime, anywhere, without compromising security. The Horizon Client can handle high-end graphics and applications and offers multiple display device support, thereby helping us improve productivity. Horizon Client versions are available for various platforms, like Windows, Linux, macOS, Google Android, etc, for accessing remote devices in virtualized environments.

Causes for Vmware Horizon client connection failed timeout was reached

  1. Network Latency or Connectivity Issues:

Network latency is the time it takes for data to travel from one device to another. It is generally measured in milliseconds and depends on various factors like physical distance, the number of network devices involved, etc. Low latency is a general indication of faster data transmission.

Network latency or connectivity problems resulting in delays or disruptions in communication between the client device and the server hosting the virtual desktop can be the primary cause of the timeout error.  As and when data packets suffer longer delays or get lost due to network connectivity issues, the Horizon Client may not receive a timely response from the server, resulting in timeouts.

  1. Server Unavailable or Overloaded

If the server cannot respond promptly to the client’s connection request, it can lead to “timeout has reached” errors. Whenever a server is unavailable or overloaded, it may be unable to handle the requests sent from the client, resulting in incomplete or delayed responses. The Horizon Client, therefore, experiences timeouts while waiting for a response from the server.

  1. Incorrect Configuration

Misconfigurations in network settings like DNS settings or IP addresses can result in a loss of communication between the Horizon Client and the Server. Firewall configurations, too, can block the ports Horizon uses for communication. Additionally, the connection timeout settings, both on the server and the client side, can need to be in sync, failing, which can lead to the said error.

  1. Incompatible Horizon Client or Server

If the versions of VMware Horizon are not compatible with each other, it can result in problems related to communication mechanisms. When the software versions of the client and the server match, they may be unable to establish a successful and consistent connection between them, and connection timeout errors may occur. Moreover, newer versions might implement new features or security protocols that the older ones may not support.

Resolution to VMware Horizon client connection failed timeout was reached

Resolving the error would consist of checking all the individual phases of the connection between the Horizon Client and the server to identify the problem correctly. The process to do so would include the below-mentioned steps:

  1. Check Network Connectivity
  2. Check Resource Usage for Horizon Server
  3. Review Configuration Settings

1] Check Network Connectivity

The first step towards resolving the error is to ensure that the physical connection between the client and the server is stable and consistent.

Physical Connection Settings

Start by checking your network connection. Ensure that you have a stable and reliable internet connection. You can run a speed test to determine if your bandwidth meets the requirements for VMware Horizon Client. If you’re using a Wi-Fi connection, try switching to a wired connection to eliminate any potential wireless interference or signal issues.

To check the DNS connection:

  • Open the Windows Terminal prompt as an Administrator.
  • Type the below-mentioned command on the Terminal Prompt.
nslookup hostname


The nslookup command allows us to enter the host system’s name and find out its IP address and DNS records. This is beneficial when troubleshooting network connectivity errors. In this case, nslookup helps us check whether the Horizon Client is able to establish a successful connection with the Horizon Server. The hostname option in the command can be replaced by the server’s hostname.

Once we confirm that the client can reach out to the server, we can check if both systems can communicate with each other over the port the Horizon Client uses as the default. To test the port, the below-mentioned command can be used to check for the communication:

telnet hostname 4002

where 4002 is the default port used by the Horizon Client.

If both commands are successfully executed, we can safely conclude that the network connection is not causing the error and move on to the next phase.

2] Resource Usage for Horizon Server

Once the connection diagnosis has been satisfactorily completed at the client end to confirm that no errors exist concerning the physical connections between the server and the client, we can check if over-utilization of the server resources is contributing to the error. Higher resource usage, like CPU or memory utilization and network bandwidth, may cause delays in communication.

Hence, from the administrator’s end, due checks on these resources and optimization can help balance the load. Additional resources can be added if needed to maintain proper network balance. To check the resource usage:

  • Open the VMware Horizon Admin Console on the server by double-clicking on the icon
  • Click on the Dashboard option under the Monitor section on the left pane.

vmware horizon connection dashboard

We can check the overall workload, system health, and session states, which can help us understand the amount of network resources currently in use.

4] Review Configuration Settings

Upon confirmation that the network connectivity and the server resources are not causing the error, the final step involves reviewing the application settings for the Horizon Client.  This step would involve checking the connection settings, including the session timeout interval.

VMware Horizon Client Settings

  • Open the VMware Horizon Client.
  • Check the connection settings within the client, ensuring the server address is correct.

vmware horizon client server info

Changing the Timeout Settings

Session timeout is when a session can remain idle between the Horizon client and the server before being disconnected automatically. The session timeout value can be set anywhere between 10 to 4320 minutes. If the timeout error occurs frequently, even when the network is stable, increasing the timeout can help avoid the error. To do so,

  • Open the Run dialogue box by pressing the Windows + R key
  • Type regedit and press Enter to open the Registry Editor.
  • Navigate to HKEY_LOCAL_MACHINE\Software\VMware, Inc.\VMware VDM\Agent\Configuration\XMLAPI
  • Increase the Session Timeout to 600.

horizon client session timeout registry settings

Setting the session timeout value (in minutes) to 600 ensures that the timeout happens only after 10 hours.

Is VMware Horizon Client a Virtual Private Network?

Horizon Client uses a unified access gateway (UAG) to allow secured remote access sessions without a VPN connection. Even though it supports a VPN connection for accessing remote resources, it is not the same as a VPN connection.

Can antivirus applications be installed on a Horizon Client system?

Horizon Clients supports the use of antivirus software in its environment to improve system performance and security.


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