This document intends to offer a detailed discussion of selected distributed object-oriented architectures at conceptual level. The first part of the discussion offers a comprehensive overview of the Socket architecture in Java 2 and Berkeley UNIX and the distributed object model of Java Remote Method Invocation and the Common Object Request Broker Architecture. The second part concludes the discussion with a comparative study of selected features with emphasis on the Common Object Request Broker Architecture and Java Remote Method Invocation. Major Issues Include The TCP/IP Protocol Suite. We provide an introductory overview of the TCP/IP protocol suite and its architecture including layers and protocols. The TCP/IP architecture is based on three concepts: processes, layers and protocols. Sockets in Berkeley Unix. We present the Berkeley UNIX socket architecture in relation to the Internet communication domain and illustrate connection-oriented and a connectionless models of communication. Sockets in Java 2. We describe the Java 2 socket architecture, outline selected socket operations, introduce related packages and classes and conclude with a framework for a connection-oriented and connectionless model of communication. Remote Method Invocation in Java 2. We present a distributed object model in Java RMI, provide an overview of related interfaces, classes and packages and discuss security related issues. We conclude with the development of a framework for a distributed object application. Common Object Request Broker Architecture. We introduce a distributed object model for the Common Object Request Broker Architecture and outline design concepts including the Interface Definition Language and the Interoperable Naming Service. We conclude with the development of a framework for a distributed object application. Comparative Study of Distributed Architectures. We present a comparative study of socket architectures and distributed object models introduced in part one of this document. Sources of Information and References This document is based on specifications, guidelines, Internet drafts and Internet standards issued by the Object Management Group consortium, Sun Microsystems, Inc. and the Internet Engineering Task Force ¿ IETF. In particular, the material for the TCP/IP protocol suit was obtained from IETF. Its responsibility includes the dissemination of Internet Drafts, referred to as Ready for Comments ¿ RFCs. The chapters on the Java 2 Socket API and the Java Remote Method Invocation architecture are based on specifications provided by Sun Microsystems, Inc. The Sockets API in Berkeley UNIX is outlined in the corresponding documentation of Release 4.2. The Common Object Request Broker Architecture is documented in great detail in the form of specifications and introductory material issued by the Object Management Group consortium.