What is eXternal Data Representation (XDR)?
eXternal Data Representation is a standard used to describe data in a format that is independent of computer, programming language or compiler conventions. This standard format is used in RPC implementations; it uses big-endian byte order and IEEE floating point format. It provides a common data foramt that can be used to communicate between computers with different architectures.
Unix SVR4 RPC comes with XDR library routines to encode and decode data between different computer architecture. Java types are mostly compatible with XDR - Java's int, long, float, and double primitive types are all identical to their XDR equivalents.