If NULL Ends a String or Char[], How to Send NULL to a File?

I have a series of codes that will include NULL bytes and other non-text
data that I need to send to a device through a file.

Since a NULL terminates a string, how do I send a string containing NULL
bytes to a file (or device, depending on the OS)?

Do I have to handle the string (or char[]) in a special way to make sure
all
the data is kept intact?

Is there a better way to handle this?

Thanks!

Hal