基于Linux的消息驱动Socket模型

在Linux下进行网络编程时通常使用Socket．Linux系统的输入输出模型主要有4种：阻塞式，非阻塞式，多路复用和信号驱动。这4种输入输出模型均具有一定的局限性，使得在Linux下的网络编程颇不方便。该文设计了一种面向对象、消息驱动的Socket摸型。     

高级网络编程接口NPORT的设计与实现

介绍了一个Unix系统下的基于API的高级网络应用编程接口NPORT的设计与实现。NPORT接口封装了API的编程细节，简化了网络应用编程。     

基于SCTP的客户/服务器的设计与实现

随着IP网向多业务网的发展,新一代运输层协议SCTP会逐渐替代TCP在下一代网络中获得更加广泛的应用。分析了SCTP/IP协议栈中数据传输过程,介绍了SCTP协议所提供给开发人员的套接口编程模型,并给出一个在Uinx/Linux系统上利用一到多形式套接口模型开发客户/服务器应用的示例。     

基于SCTP的客户/服务器的设计与实现

随着IP网向多业务网的发展,新一代运输层协议SCTP会逐渐替代TCP在下一代网络中获得更加广泛的应用。分析了SCTP/IP协议栈中数据传输过程,介绍了SCTP协议所提供给开发人员的套接口编程模型,并给出一个在Uinx/Linux系统上利用一到多形式套接口模型开发客户/服务器应用的示例。     

Internet网络环境的测试程序设计与实现

在ＩＣＭＰ及ＩＰ协议下,讨论了基于Ｕｎｉｘ环境的任务客户端,通过Ｉｎｔｅｒｎｅｔ网络环境是否可任何服务器端的测试程序设计,主要介绍了利用ｓｏｃｋｅｔ接口客户端测试程序的设计与实现。     

The Unix System and Software Reusability

The Unix system contains a variety of facilities that enhance the reuse of software. These vary from the utterly conventional, such as function libraries, to basic architectural mechanisms, such as the Unix pipe. The Unix pipe, which makes whole programs building blocks of larger computational structures, has been the primary reason for the development of a literature of useful, but specialized programs-programs that would be too costly to write in a conventional programming language such as C. It has led to high levels of program reuse both by the nature of its operation and through its effect on programming conventions (e.g., programs structured as simple filters). Another facility enhancing reuse on Unix is the on-line C source code for Unix system programs. This has led to a shared style of programming in which existing programs are used as models for new programs, allowing the reuse of ideas, algorithms and source code. Finally, the Unix system contains many other reuse enhancing facilities, such as generic facilities for screen management (curses and termcap) and program generators (lex and yacc).     

Connecting tools using message passing in the Field environment

An overview is given of the Field environment, which was developed to show that highly integrated, interactive environments like those on PCs can be implemented on workstations and can be used for classical-language and large-scale programming. Field connects tools with selective broadcasting, which follows the Unix philosophy of letting independent tools cooperate through simple conventions, demonstrating that this simple approach is feasible and desirable. Field achieves its goals by providing a consistent graphical front end and a simple integration framework that lets existing and new Unix tools cooperate. The front end is based on a tool set called the Brown workstation environment. The framework combines selective broadcasting with an annotation editor that provides consistent access to the source code in multiple contexts and with a set of specialized interactive analysis tools. Field's integration framework and message facility are described     

Experimenting with dynamic linking with ADA

An approach to achieving dynamic reconfiguration within the framework of Ada¹ is described. A technique for introducing a kernel facility for dynamic reconfiguration in Ada is illustrated, and its implementation using the Verdix VADS 5.5 Ada compiling system on a Sun3–120 running the 4.3 BSD Unix operating system is discussed. This experimental kernel allows an Ada program to change its own configuration dynamically, linking new pieces of code at run-time. It is shown how this dynamic facility can be integrated consistently at the Ada language level, without introducing severe inconsistencies with respect to the Standard semantics.     

An Installable Version Control File System for Unix

We present a file system named VCFS, a Version Control File System that provides transparent version control of files. VCFS is implemented as an installable file system in the Unix operating system. The facility is transparent to users in the sense that VCFS automatically stores changes between incremental versions of a file without user intervention. Access to the latest version of the file retains traditional Unix semantics, enabling all existing Unix applications to be run modified under VCFS if so desired. VCFS provides system call enhancements and supports application level utilities for version number retrieval, displaying changes between two versions of a file, upgrading to a new release number, and related version control functions. Performance measurements show that VCFS provides a significant increase in version control operations compared to application level change management systems such as SCCS, and that the space utilization is significantly better than of the existing version control systems. The primitives and facilities provided by VCFS can be exploited for use in a wide range of applications, ranging from immutable files, transaction processing and file replication support in a distributed file system, to the development of enhanced change management control systems for software project management. © 1997 John Wiley & Sons, Ltd.     

On distributed fault simulation

The authors examine the computational aspects of fault simulation of digital circuits and address issues related to the efficient partitioning of a fault simulation task to a number of subtasks assignable for execution to the nodes of a distributed system. They review the basic concepts involved in the operation of fault simulation. They describe the implementation of a distributed fault simulation facility, called DFSim, using a heterogeneous local area network consisting of a number of workstations with different computing resources and different versions of Unix operating systems     

The Alloc Stream Facility: a redesign of application-level streamI/O

The authors introduce an application-level I/O facility, the Alloc Stream Facility, that addresses three primary goals. First, ASF addresses recent computing substrate changes to improve performance, allowing applications to benefit from specific features such as mapped files. Second, it is designed for parallel systems, maximizing concurrency and reporting errors properly. Finally, its modular and object-oriented structure allows it to support a variety of popular I/O interfaces (including stdio and C++ stream I/O) and to be tuned to system behavior, exploiting a system's strengths while avoiding its weaknesses. On a number of standard Unix systems, I/O-intensive applications perform substantially better when linked to the Alloc facility. Also, modifying applications to use a new interface provided by the facility can improve performance by another factor of two. These performance improvements are achieved primarily by reducing data copying and the number of system calls. Not visible in these improvements is the extra degree of concurrency the facility brings to multithreaded and parallel applications     

基于知识库的Unix主机配置安全审计软件的设计与实现

配置安全审计是保证Unix主机安全的重要措施,并进一步为Unix操作系统所承载的业务应用提供了安全保障。本文首先分析Unix操作系统的配置安全和传统的配置安全审计方法,并针对传统方法的不足,提出一种基于可灵活配置的知识库实现Unix操作系统配置安全审计软件的设计方案,最后给出这种方案的具体实现。     

Subjective impressions of a non-naïve Unix and c beginner

This paper details an experienced programmer's first impressions of working with the Unix operating system and c programming language. Use of the Unix shell, vi editor, c compiler and some utilities are discussed, as are the Unix documentation and some relevant textbooks. An assessment of the difficulties and advantages of starting with Unix is given.     

BPF的实现机制分析与性能优化研究

BSD包过滤器(BSD Packet Filter,BPF)是BSD Unix操作系统提供的网络数据包捕获及过滤机制的内核组件。该文描述了BPF的组成及工作过程,分析了BPF采用的无环控制流图过滤模式,介绍了此模式基于虚拟机的实现。为了提高过滤器性能,必须解决BPF虚拟机指令生成器处理多个过滤条件组合时存在的指令冗余问题,通过引入静态单赋值(SSA),结合冗余谓词消除和窥孔优化等技术,可以有效缩短CFG图的平均路径长度,从而实现对过滤器性能的优化。     

Ｕnix实时性研究

针对传统Ｕnix在实时应用方法存在的主要问题进行了分析,讨论了Ｕnix的实时特性和调度策略;并结合实际应用,通过附加一个实时库,增加一些实时功能的方法,阐述了Ｕnix在实时Ｉ／Ｏ、内存管理、进程调度、时钟和定时器等方面的实现策略。     

An interrogative visualization environment for large-scale engineering simulations

An interrogative visualization environment is described for the interactive display and querying of large datasets. The environment combines a web-based intelligent agent facility with a visualization engine. The intelligent agent facility (IAF) incorporates a rule-based expert system for natural-language understanding, voice and text input facilities, a hierarchical clickable command list, an interface for multimodal devices such as menu-based wireless handheld devices and gesture recognition devices, and human-like avatars acting as virtual assistants. The IAF interacts with, and controls, the visualization engine through a TCP/IP network socket interface. The environment enables multiple users using a variety of interaction modes and devices to effectively browse through large amounts of data, focus on and query interesting features, and more easily comprehend and make use of the data. Application of the environment to the visualization of engineering simulations is described.     

Utopia: A load sharing facility for large,heterogeneous distributed computer systems

Load sharing in large, heterogeneous distributed systems allows users to access vast amounts of computing resources scattered around the system and may provide substantial performance improvements to applications. We discuss the design and implementation issues in Utopia, a load sharing facility specifically built for large and heterogeneous systems. The system has no restriction on the types of tasks that can be remotely executed, involves few application changes and no operating system change, supports a high degree of transparency for remote task execution, and incurs low overhead. The algorithms for managing resource load information and task placement take advantage of the clustering nature of large-scale distributed systems; centralized algorithms are used within host clusters, and directed graph algorithms are used among the clusters to make Utopia scalable to thousands of hosts. Task placements in Utopia exploit the heterogeneous hosts and consider varying resource demands of the tasks. A range of mechanisms for remote execution is available in Utopia that provides varying degrees of transparency and efficiency. A number of applications have been developed for Utopia, ranging from a load sharing command interpreter, to parallel and distributed applications, to a distributed batch facility. For example, an enhanced Unix command interpreter allows arbitrary commands and user jobs to be executed remotely, and a parallel make facility achieves speed-ups of 15 or more by processing a collection of tasks in parallel on a number of hosts.     

Practical experience with OS/2 installable file systems

The installable file system (IFS) faculty on OS/2 offers an efficient mechanism for expanding the abilities of the OS/2 kernel. Two prototypes illustrate the usefulness of the IFS facility. An OS/2 port of the Andrew File System (AFS) allows users to access global community files while retaining the private local file system on the OS/2 machine. An IFS implementation of a network protocol mapper, which maps TCP/IP socket calls to SNA Advanced Program-to-Program Communication (APPC) calls, provides the ability to run any socket program on an APPC network after simply re-linking with the mapping library. The only impediment to the development of these prototypes is the lack of kernel-level interfaces to operating system devices, resulting in time-consuming data movement back up to the user level to access the network and the local disks. This impediment will disappear as OS/2 and its associated support software matures.     

基于Socket的跨平台数据监测网络编程方法

在研究了Unix平台和Windows平台下网络编程技术的基础上,对Unix平台下开发的数据处理服务器采用异构平台监测方法,实现跨平台的网络编程,发挥了Unix和Windows两种操作系统各自的优点,实现低成本、高收益的服务器功能扩展.