Java Remote Method Protocol or JRMP is the Java technology-specific protocol for looking up and referencing remote objects. It is a wire level protocol running at the level under Java remote method invocation (RMI) and over TCP/IP.
Details
JRMP is a Java-specific, stream-based protocol for Java-to-Java remote calls, requiring both clients and server to use Java objects. RMI-IIOP is an alternative protocol which exposes Java objects to CORBA ORBs. Many application server vendors have developed their own protocols for use with RMI which claim to offer advantages over both IIOP and JRMP.
References
Java Remote Method Protocol Wikipedia(Text) CC BY-SA