about tcp port 53

[Stephane Bortzmeyer]

On Mon, Jul 27, 2009 at 10:33:56AM +0800,
 Tech W. <techwww at yahoo.com.cn> wrote 
 a message of 23 lines which said:

> what's the use of bind's tcp port 53?

DNS requests and responses.

> is it used for dns update and zone transfer or something else?

Everything else.

> If I have not been using dynamic update and transfer, can I block
> tcp port 53 using a firewall?

Certainly not.