RPC

SOAP

• Simple Object Access Protocol
  
• Text-based protocol

SAAJ

• SOAP with Attachments API for Java

Java RMI

• Remote Method Invocation
• JRMP or RMI-IIOP
• Binary format

• The term "RMI" is often used to refer to JRMP

JRMP

• Java Remote Method Protocol
• Effective for Java-to-Java communication
• Binary protocol

• The earliest option for Java RMI

RMI-IIOP

• Internet Inter-Orb Protocol
• A simplified form of CORBA for RMI
• Binary protocol

• Effective for communication in a heterogenous environment that uses a number of programming languages

XML

• Text-based format

JAX-RPC

• Java API for XML-based RPC
• Converts an RMI into a SOAP message
• Text-based protocol

• Java RMI for web services
• Used in combination with a WSDL description
• Maps XML elements to Java objects and properties