## Appendix B. Troubleshooting

### Troubleshooting: `xxeserver` does not start

- An error message similar to the following one is displayed in the terminal or Command Prompt used to start `xxeserver` or is found in `xxeserver` log file.

      xxeserver: cannot start server: Failed to bind to 0.0.0.0/0.0.0.0:18078

  Possible causes:
  - `xxeserver` is already running.
  - OR the port 18078 is used by another server. On Linux, command "`lsof -i :PORT_NUMBER`" will tell you which server is currently listening to port PORT_NUMBER.

### Troubleshooting: the sample XML editor web application does not work

- When opening the HTML page containing the sample XML Editor, you see the following error message:
  Possible causes:
  - The sample XML editor web application loads fine but your web browser is really not supported (e.g. Safari, any mobile web browser).
    You need to switch to a very recent version of Google Chrome or to any browser using the same Blink browser engine: Edge, Opera, Brave, etc. Firefox works fine too, but without system clipboard integration.
- When opening the HTML page containing the sample XML Editor, you see the following error message:
  Possible causes:
  - The sample XML editor web application did not load. You are using a somewhat obsolete web browser (e.g. Internet Explorer) or your web browser is supported but you have disabled its JavaScript support.
- Opening the HTML page containing the sample XML Editor seems to work but using the New or Open button displays the following error dialog box:
  Possible causes (assuming that `xxeserver` and the sample XML editor web application are correctly configured):
  - `xxeserver` is not running.
  - OR the port used by `xxeserver` (18078 in the above screenshot) is blocked by your anti-virus, firewall or proxy.