MessagingTool is a simple so-called chat tool. But its origin goes way back to 1980s. Originally MessagingTool was implemented in Mesa language and run on top of XDE (Xerox Development Environment), using the XNS (Xerox Network Systems) protocol.
In 1991, I implemented another MessagingTool in C language which supported both the XNS protocol and TCP/IP protocol: actually this C version used TCP/IP-based Sun's RPC. This C version could be used to exchange messages with the Mesa version becuase it supported the XNS protocol.
In Summer, 1996, I started to learn Java language and implemented another MessageTool in Java. This Java version is not compatible with the Mesa and C versions: this Java version uses TCP/IP but not Sun'S RPC. Originally, the Java version was implemented with Java 1.02 which didn't support inner class.