Frontend server connection issues

Modified on Thu, 20 Jul, 2023 at 12:22 PM

When you encounter connection issues, first check the status of the frontend server. To check it, go to the URL http://formcycle.eu/frontend-server.

No connection: ERROR

No connection: NOT_CONNECTED

Connection status: CONNECTED

Connection status

connected	note
true	A connection to the master server could be established successfully.
false	There is no connection to the master server.

Logical status

There are several possible values for the connection status that you might see:

Status	Description
CONNECTED	The connection has been established and opened.
NOT_CONNECTED	No connection could be established.
ERROR + error message	An error has occurred while trying to establish a connection. Usually an error message with details will be shown.
DISCONNECTING	The connection is about to be closed.
WAIT_FOR_CONNECTION	The frontend server has been started successfully and is listening on the configured port for an initial connection attempt by the master server.
RECONNECTING	The server is trying to reconnect after the connection was disrupted.
CONNECTING	The server is trying to establish a connection.
AUTHENTICATING	The connection was established and the permissions are checked.

HTTP status

The HTTP status code that is returned when you open the frontend server status page. For example, you can use this status code to check the connection programmatically without having to parse the HTML status page.

200: There is a connection to the master server.
503: No connection could be made to the master server.

Handling errors

It is important to ensure that the same major Java version is used for the master and frontend server. If this is not the case, no connection can be established between the servers, even if the connection test was successful at some times.

Initial connection fails

Check whether the frontend server has been started successfully and whether it is listening on the correct port.
When it is: Check whether the frontend server can be reached from the master server, for example via Telnet. Possibles reasons it may not be reachable include:
1. The firewall is blocking any connection attempt on the configured port.
2. The network architecture prevents the servers from seeing each other.
When the above applies: Check whether a key has already been assigned to the frontend server. When a key has already been assigned, an error message as shown in the screenshot to the right indicates this.
Sometimes restarting the application or the server may solve the issues.

Connection closed (Connection could be established before)

When the connection to the frontend server cannot be established again automatically, it can be opened manually from the master server.

This requires the following steps:

Open the configuration interface of the master server in a web browser
Login to the master server with a valid system administrator account (username sadmin).
Go to the frontend server menu under system. Try to establish a connection manually by pressing on the reconnection button.
When you a success message, the connection has been established successfully.

Other issues

Should all these measures fail, try the following:

Connect to the frontend server
Restart the Tomcat application of the frontend server
Open the status page of the frontend server in a browser with the following URL: http://localhost/fs
When the status displays as NOT_CONNECTED or WAIT_FOR_CONNECTION, you need to reconnect to the master server, see above.
Open the status page of the frontend server again. It should now show the status CONNECTED.
Should this fail too, the Tomcat of the master server should be restarted.
Afterwards, check again if the connection has been established automatically, either by opening the configuration interface of the master server or by accessing the status page of the frontend server directly.
It may be necessary to establish the connection manually, see above.