I must say, I have programmed both with sockets and RMI/CORBA - both with the same objective in mind.
Sockets seem easier to control, where something like CORBA could take a lot of time to learn. RMI would limit you client to needing to be another Java application. In case you don't know, RMI is a Java only version of CORBA.
Sockets would limit your client applications to also being Java based if you choose to write objects across the stream (So in answer to your question, yes you can serialize and send objects across a network)
sockets could be client independent (c++,.NET, etc) if you choose to just write bytes across the network. However writing bytes you would need to make some sort of protocol for communications, this can be a lot of work, and if you get errors and need to debug problems by reading byte streams... your in for a tough time.
CORBA is good for business. It allows you to read and write objects, and call methods on remote objects, and its highly optimized, its a mature technology, having been around well over 10 years. It allows your Java application to communicate with ANY other client, c++, .NET, etc
My advice. If your programming games, chat programs, streaming media, file transfer use sockets and read/write bytes. You have tighter control over what is sent, you can optimize the streams, by buffering, or compressing date.
If you programming business applications which require remote method calls, use CORBA, (or if the client is definitly Java, you could use RMI). Corba however would be useless for lets say, file transfer, or any streaming type app.
Hope that helps
