For developing our application to communicate on network irrespective of platform or language we are using Web Services technology. The standards to develop these applications is given by WS-I (Web Services Interoperability Organization).
So, what languages provided what API's to develop these Applications.
As of my Knowledge, for JAVA
Network Communication(HTTP) - Servlet/EJB API
XML - JAXP (Java API for XML Processing), JAXB (Java Architecture for XML Binding)
UDDI - JAXR (Java API for XML Registries)
SOAP - SAAJ (SOAP with Attachments API for Java)
WSDL - WSDL4j
WS-I released two versions.
Java released JAX-RPC API for BP 1.0, JAX-WS API for BP 1.1
NOTE: Correct me, if I am wrong