Send command to a background process

Question

I have a previously running process (process1.sh) that is running in the background with a PID of 1111 (or some other arbitrary number). How could I send something like

Answer 1

For how to send commands to a server via a named pipe (fifo) from the shell see here:

Redirecting input of application (java) but still allowing stdin in BASH

How do I use exec 3>myfifo in a script, and not have echo foo>&3 close the pipe?