Well, this is an awfully generic question. If you're just wondering about how to transfer the raw contents of the files, then just avoid using Readers or Writers; use InputStreams and OutputStreams, and all your data will be transferred as the raw, unadulterated file contents.
If you're asking how to open files, how to do networking, etc, well, you'll have to ask those one at a time. Or you could checkout the networking and I/O sections of
Sun's Java Tutorial. You can then come back here with specific questions.