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Perform a Telnet Test for Windows

Catherine Harper
  • Updated
  1. Shift4 Payments
  2. Self Help Product Categories
  3. Universal Transaction Gateway (UTG)
  4. Troubleshooting

Description: Telnet is a program available in many installations of Windows that allows one machine to connect to another to perform commands or testing. Performing a Telnet can allow you to verify that one computer is able to communicate to another over a network using the IP Address and Port provided. If a Telnet fails, this will often indicate a port restriction or that the destination IP is unavailable.

Note: Windows 7 and above may not have this function installed by default and, if not, will return a "Command not recognized" error when run. 

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Running A Telnet Test

  1. Open up Windows Command Prompt or PowerShell. Refer to the Access Windows Command Prompt or PowerShell article for additional information.
  2. In the prompted window that appears, input telnet [ip address] [port] (i.e. "telnet 192.168.1.1 17476" without quotes) where [ip address] is the IP address we're trying to reach and [port] is the port number configured for communication and select Enter.

It is important to be aware of what you're troubleshooting to determine what the destination IP should be. For example:

  1. Interface cannot communicate to UTG: The Interface is attempting to submit transaction data to the UTG. Telnet should be performed from the Interface Server/Terminal to the UTG machine, meaning the IP address listed should be that of the UTG machine. Use the port configured for the API interface the affected POS communicates to.
  2. Stub cannot communicate to UTG: When using Stub, the Interface sends a command to the UTG and the UTG then opens communication with the Stub which then utilizes the open socket for communication; ergo, if the communication issue is with the Stub, we should be running Telnet from the UTG machine to the Stub machine using the IP address and port listed in the device thread for the affected terminal. 
  3. 4Go cannot communicate with UTG: 4Go sends the faux card data to the UTG prior to sending it through the interface. That said, if 4Go can't communicate then we will want to run the telnet from the affected Terminal to the UTG using the IP address and port listed for the API interface thread where the 4Go requests are sent. This could be the same thread where the POS is sending transactions or it could be a separate thread.

If you receive an error response then this indicates a networking issue that will need to be resolved by your IT.

The error may give some insight as to what is being experienced however we cannot interpret these messages on our end. We may suggest a possible port restriction or firewall issue as these are common causes of failed Telnet responses. We may want to verify that the UTG is added as a Windows Firewall exception. Refer to the Adding The Universal Transaction Gateway (UTG) or UTG Stub To The Windows Firewall.

A blinking cursor on a blank black screen indicates that Telnet is waiting for command input, meaning that a successful connection to the IP address over the Port listed was made. This will rule out communication to the IP over the listed Port as a possible cause, meaning focus should shift back to the UTG and/or Interface configuration to determine why communication is breaking down.

Enabling Telnet In Newer Windows Versions

Note: This can introduce security vulnerabilities into the merchant's network environment, So after testing is complete you must also walk them through disabling telnet. Simply follow the same direction and instead un-check the Telnet Client box; when you select OK, Windows will uninstall Telnet.

If you are unable or unwilling to enable Telnet, you may opt to utilize the UTG Browser Test. 

  1. Open Programs and Features on the computer:
    • For Windows 7: From the Start menu open the Control Panel and then select Programs and Features
    • For Windows 10: Right-click the start button and select Programs and Features
  2. In the top left there should be a button for Turn Windows Features On or Off (This will require an admin login.)
  3. From the Windows Features window, scroll down until you reach Telnet Client.
  4. Select the checkbox next to Telnet Client and select OK.
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  1. Telnet will then be installed, when Windows has finished:
    • For Windows 7: The "Windows Features" window will close automatically when this has finished.
    • For Windows 10: A dialog box appears to confirm the installation. The telnet command should now be available.
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