What can cause SIGHUP to be generated?

Signals can be sent using kill utility or kill syscall. Of course, you can try and find out who is sending that signal or disconnecting your terminals or network connections, but there is simpler practical way to fix your problem.

When code is supposed to run as a daemon, but really isn't (just like yours), there is a wrapper that can turn any program into daemon. Surprise - this wrapper is called daemon! It has lots of options, probably most importantly for you, option to automatically restart your utility should it ever die for any reason.

If this command is not installed on your Ubuntu, just sudo apt-get install daemon, and man daemon to get started.

Well, there are a couple of things to note about SIGHUP. Firstly, its origin is from the concept of a hang-up, i.e. loss of connection to a console over something like a modem. In modern parlance this generally means it has lost its controlling tty. Unless you've taken care to detach from your tty, any program started in a given terminal will receive a SIGHUP when the terminal is closed. See here for details on how to do this in your program. Other options include:

• running your program inside screen or tmux
• run your program with nohup or some other daemonising framework

The other possibility is something is deliberately sending your process a SIGHUP which by "tradition" is often used to signal a process that it should re-read its configuration.