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$Id: README 96983 2013-04-11 11:14:11Z schmidt $

This document is also available at the following URL:

All software and documentation is available via both anonymous ftp and
the http.]


An Object-Oriented Network Programming Toolkit


Overview of ACE

The ADAPTIVE Communication Environment (ACE) is an object-oriented
(OO) toolkit that implements fundamental design patterns for
communication software.  ACE provides a rich set of reusable C++
wrappers and frameworks that perform common communication software
tasks across a range of OS platforms, including Win32/Win64, most
versions of UNIX (e.g., SunOS, HP-UX , AIX, Linux, NetBSD, and FreeBSD),
real-time operating systems (e.g., VxWorks, Chorus, LynxOS, and QNX),
OpenVMS, and MVS OpenEdition.  A single source tree is used for all
these platforms and porting ACE to other platforms is relatively easy.

The communication software components provided by ACE include event
demultiplexing and event handler dispatching, service initialization,
interprocess communication, shared memory management, message routing,
dynamic (re)configuration of distributed services, multi-threading,
and concurrency control.  There are both C++ and Java versions of ACE

ACE is targeted for developers of high-performance and real-time
communication services and applications on UNIX, POSIX, and Win32
platforms.  ACE simplifies the development of OO network applications
and services that utilize interprocess communication, event
demultiplexing, explicit dynamic linking, and concurrency.  ACE
automates system configuration and reconfiguration by dynamically
linking services into applications at run-time and executing these
services in one or more processes or threads.

ACE is currently used in commercial projects and products by dozens of
companies including Ericsson, Bellcore, Siemens, Motorola, Kodak,
Boeing, Lucent, DEC, Lockheed Martin, and SAIC.  Commercial support
for ACE is available from several companies as listed at


C++ Wrappers for OS Interfaces

The lower-level portions of ACE provide a set of portable and
type-secure C++ wrappers that encapsulate the following C language OS

        . IPC mechanisms
                -- e.g., Internet- and UNIX-domain sockets, TLI, Named
                   Pipes (for UNIX and Win32) and STREAM pipes;

        . Event demultiplexing
                -- e.g., select(), poll(), and Win32
                   WaitForMultipleObjects and I/O completion ports;

        . Multi-threading and synchronization
                -- e.g., Solaris threads, POSIX Pthreads, and Win32

        . Explicit dynamic linking
                -- e.g., dlopen/dlsym on UNIX and LoadLibrary/GetProc
                   on Win32;

        . Memory-mapped files and shared memory management
                -- e.g., BSD mmap(), SYSV shared memory, and Win32
                   shared memory;

        . System V IPC
                -- e.g., shared memory, semaphores, message queues.

The OS Adaptation Layer shields the upper levels of ACE from platform
dependencies associated with the underlying OS interfaces.


Frameworks and Class Categories

ACE also contains a higher-level network programming framework that
integrates and enhances the lower-level C++ wrappers.  This framework
supports the dynamic configuration of concurrent distributed services
into applications.  The framework portion of ACE contains the
following class categories:

        . The Reactor
                -- Supports both Reactive and Proactive I/O;

        . The Service Configurator
                -- Support dynamic (re)configuration of objects;

        . The ADAPTIVE Service Executive
                -- A user-level implementation of System V STREAMS,
                   that supports modular integration of
                   hierarchically-related communicaion services;

        . Concurrency
                -- Various types of higher-level concurrency
                   control and synchronization patterns (such as
                   Polymorphic Futures and Active Objects);

        . Shared Malloc
                -- Components for managing dynamically allocation
                   of shared and local memory;


Distributed Services and Components

Finally, ACE provides a standard library of distributed services that
are packaged as components.  These service components play two roles
in ACE:

        1. They provide reusable components for common distributed
           system tasks such as logging, naming, locking, and time

        2. They illustrate how to utilize ACE features such as the
           Reactor, Service Configurator, Service Initialization,
           Concurrency, and IPC components.


Middleware Applications

ACE has been used in research and development projects at many
universities and companies.  For instance, it has been used to build
avionics systems at Boeing, telecommunication systems at Bellcore,
Ericsson, Motorola, and Lucent; medical imaging systems at Siemens and
Kodak; and many academic research projects.  Two example middleware
applications provided with the ACE release include:

        1. The ACE ORB (TAO) -- TAO is a real-time implementation of
           CORBA built using the framework components and patterns
           provided by ACE.

        2. JAWS -- JAWS is a high-performance, adaptive Web server
           built using the components in ACE.



ACE may be obtained electronically from  This release contains the source
code, test drivers, and example applications (including JAWS) for C++
wrapper libraries and the higher-level ACE network programming
framework developed as part of the ADAPTIVE project at the University
of California, Irvine, Washington University, St. Louis, and
Vanderbilt University.

You can get The ACE ORB (TAO) in a companion release at the same URL.



Many of the C++ wrappers and higher-level components have been
described in issues of the C++ Report, as well as in proceedings of
many journals, conferences, and workshops.

A collection of white papers and tutorial handouts are included at

This page contains PDF versions of various papers that describe
different aspects of ACE.

This material is also available available via the WWW at URL:



A mailing list,, is available for
discussing bug fixes, enhancements, and porting issues regarding ACE.
Please send mail to me at the if you'd like to join the
mailing list.  There is also a USENET newsgroup called
comp.soft-sys.ace. Please see for details on
how to subscribe to the mailing list.



Please refer to the file for
information on how to build and test the ACE wrappers.  The
BIBLIOGRAPHY file contains information on where to obtain articles
that describe the ACE wrappers and the ADAPTIVE system in more detail.

The current release has been tested extensively, but if you find any
bugs, please report them to the ACE mailing list using the
$ACE_ROOT/PROBLEM-REPORT-FORM.  Please use the same form to submit
questions, comments, etc.  To ensure that you see responses, please do
one of the following:

    1) Subscribe to the ace-users mail list, by sending email with
       contents "subscribe ace-users" to

    2) Or, monitor the comp.soft-sys.ace newsgroup for responses.



Please see the file `$ACE_ROOT/THANKS' for a list of the thousands of
people who've contributed to ACE and TAO over the years.