System Process - Why is it using my Port??

My ESET Mirror recently stopped serving up file and I found that moving it to a different port resolves the problem.

BUT I want to put it back on the default port (2221). When checking netstat I found that is is PID 4 which is the 'System' process.

Is there a simple way of telling System to 'back off' so ESET can claim back it port?!

Thanks