Robot Tray Error: An existing connection was forcible closed by the remote host

Robot Tray throws the following error when trying to connect to Orchestrator: An existing connection was forcible closed by the remote host.

Robot Tray shows: An existing connection was forcible closed by the remote host

When this error occurs, the robot will shows as disconnected in Orchestrator and when trying to connect the robot from the Robot tray, an error will be generated that says:

Error: An existing connection was forcible closed by the remote host
This error means that the connection to Orchestrator was closed by either Orchestrator or by an intermediator between Orchestrator and UiPath.

Diagnosing the issue
  1. Login to the Robot machine.
  2. Open a command prompt.
  3. Type “nslookup <Orchestrator hostname>”
    1. For example if the Orchestrator URL is https://orchestrator.com, the hostname would be orchestrator.com.
    2. If this command shows unresolved, try using ping.
  4. Determine the IP address of the Orchestrator host as seen by the Robot.
  5. Login to the Orchestrator machine.
  6. Open a command prompt.
  7. Type “ipconfig”
  8. This will return the actual IP address of the Orchestrator machine.
  9. Verify that the IP address is the actual IP address of the Orchestrator server.
    1. If the IP address matches the Orchestrator IP address, then go to the section Troubleshooting Orchestrator
    2. If the IP addresses do not match, go to the section Troubleshooting Intermediator

Troubleshooting Intermediator
  1. If the Robot machine is in the same domain as the Orchestrator server go to the section Hosts File Test (i.e. The Robot machine can access the Orchestrator IP address. You can test this by using ping on the Robot machine).
  2. At this point the best thing is to contact a system administrator and provide them with the following information:
    1. The IP address that the Orchestrator server gets resolved to on the Robot machine.
    2. Explain to them that the connection is being forced closed.
  3. The admin should be able to check the logs of any load balancer or proxy that sits in between the Orchestrator and the Robot server.
    1. For load balancers, make sure that everything is set to work over port 443.
  4. Usually once the issue is brought to an admin’s attention, they can find the root cause of the issue. If this is not the case, please contact UiPath Support for additional help.

Hosts File Test
  1. On the Robot machine open file explorer and go to “C:\Windows\System32\drivers\etc”
  2. Copy the file “hosts” to the desktop.
  3. Open the file and add the following line:
    1. Line to add: <orchestrator ip>     <orchestrator hostname>
    2. For example, if the ipaddress for orchestrator is 10.10.10.10 and the hostname is orchestrator.com, the line to add would be:
10.10.10.10      orchestrator.com
  1. This change will allow the Robot machine to bypass the DNS of the network and connect to Orchestrator directly.
  2. Try connecting the Robot Tray. If the first attempt fails wait a minute and then try again.
  3. If the connection succeeds, this means the problem is not with the Orchestrator server, but with whatever is between Orchestrator and the Robot Machine. At this point go back to the section Troubleshooting Intermediator
  4. If the connection fails, go to the section Troubleshooting Orchestrator

Troubleshooting Orchestrator
  1. If the Robot machines is connecting directly to Orchestrator and this error is encountered, it means that the Orchestrator is terminating the connection.
  2. Login to the Orchestrator Server as an Admin.
  3. Open a Run window and type “eventvwr” – This will open the Event Viewer.
  1. In the Event Viewer window, go to “Event Viewer (Local) -> Windows Logs->Application
  2. Click “Filter Current Log…” in the right “Actions” pane window.
  3. In the “Filter Current Log” dialog box, choose the Event Source: “Orchestrator” and “Orchestrator.BusinessException”. Then select “OK”.
  1. See if any errors associated with Orchestrator shed light on the root cause.
  2. Also check any anti-virus logs to see if they forced the connection closed.
    1. Try clearing the event viewer filter and check if any anti-virus logs were generated.
  3. If the Robot was connecting to Orchestrator directly, there will probably be some information contained in the log that explains why the connection was terminated. This information usually gives systems admins enough information to understand what the problem is.
  4. If the logs do not help resolve the issue, please open a ticket with UiPath.