Java applet - UDP or TCP?

["estratosapiens" <dberenguer@xxxxxxxxxxxxxxxxxxx>]

I was planning to develop a Java Web applet that should stablish a
communication socket with the Web server. This Web server already
"speaks" xAP, so, I thought about the possibility of using xAP
between
the Web server and the Java applet (instead of the typical TCP socket
connection). I have some doubts:

Using UDP instead of TCP is not (maybe) a good idea when communicating
over Internet. Here I have no more idea than what I've read in some
posts. Has anyone get xAP to work over Internet? Problems with routers?

If I decide not to use xAP or UDP for this application, is there any
communication standard for home/industrial automation and related with
TCP client/server connections? I know Modbus but I'm not sure whether
it's TCP oriented.

As you see, I'd like to avoid dealing with different communication
protocols. Nevertheless, I know that every thing has its place.

Any light over this subject is wellcome.

Thanks in advance,

Daniel.