I can build my app for Mac, run it in terminal and access website via browser.
Building for linux 64-bit, running it in Terminal, I see my debug message from app.open, but that I come back to terminal prompt.
Like something failed, but no error message.
I see in debug mode, there may be an error “ServerSocket could not be started” printed to console.
But not in deployment. <https://xojo.com/issue/50466>
[quote=360722:@Christian Schmitz]with port 9001 it does start indeed, with or without the background option.
The problem seems now to be that some firewall still blocks.[/quote]
Try disabling SELinux?
Sometimes that block applications from accessing ports.