Global J. of Engng. Educ., Vol.7, No.2 © 2003 UICEE Published in Australia Client-Server and Gateway Systems for Remote Control in Engineering Education* Hartmut Ewald Fachbereich Elektrotechnik und Informationstechnik, Rostock University Albert Einstein Straße 2, D-18051 Rostock, Germany George F. Page School of Engineering, Liverpool John Moores University Byrom Street, Liverpool, L3 3AF, England, United Kingdom With the rapid development of the Internet over recent years, in conjunction with the transmission protocol TCP/IP and the latest version of hypertext (HTML) facilities, new opportunities have come into existence for the use of the network for the remote control of experiments and other practical systems in engineering education. There are two prime benefits: students learn how network systems work and also how remote control technologies operate and the universities save money when students from several institutions utilise the same expensive equipment. Using graphical software environments in client-server systems can be easily designed. Client-server systems have some general advantages when compared with simple Remote-Access Systems (RAS) or proprietary (single-solution) systems. In recent years, gateway systems for remote control have become available for most measurement and instrumentation bus systems and this effectively permits direct access via LAN/Internet with a minimum of the transfer data-rates needed for control. INTRODUCTION Internet for remote control. It is now possible to design http-based client-server solutions and gateway The remote control of installations and systems has systems for remote control problems with modest been a technical reality in research laboratories and expenditure with the aid of graphical software automated industries for many years, particularly in development packages, such as LabVIEW [1][2] or process control industries. Due to the stringent VEE PRO [3]. demands of industry, a variety of bus systems have The following institutions jointly undertook a remote- been developed to operate at the different hierarchi- control project: cal levels found in automated systems. Some examples of these demands are process control • Liverpool John Moores University, Liverpool, monitoring, the updating of services software at a England, UK; distance and embedded Web-server services. • Hochschule Wismar – University of Technology, At the highest level (Intranet), Ethernet-based Business and Design, Wismar, Germany; systems are frequently utilised to transfer data, using • Rostock University, Rostock, Germany. different protocols. With the rapid development of the Internet within the last ten years, and its associated The goal of this project, which was started four transfer control protocol/Internet protocol TCP/IP, years ago, has been to increase the attractiveness and as well as the use of hypertext documentation as a effectiveness of laboratory work in research by basic technique on the World Wide Web (WWW), remote-controlled experiments. new possibilities have arisen for the utilisation of the An attractive consequence of this development is *A revised and expanded version of a paper presented at that resources are saved because the partners need the 6th UICEE Annual Conference on Engineering not cater for the whole spectrum of possible (and Education, held in Cairns, Australia, from 10 to 14 mostly expensive) research and teaching equipment February 2003. and experiments, which also have to be updated and 201 202 H. Ewald & G.F. Page maintained. Researchers from other locations could the server side. With the introduction of the HyperText control and monitor their own experiments and inves- Mark-up Language (HTML) several years ago, and tigations from a distance. the associated hypertext transfer protocol, the possi- The concept and the advantages of using a bility existed for communication between client and http-based client-server system for remote control server using graphical elements (image maps). have already been discussed elsewhere [4]. The The performance and functionality of http-based availability of gateway systems for LAN/RS232 and client-server systems has been extended through LAN/GPIB have opened up new possibilities for the server extensions such as Java, the Common remote controlled laboratory, particularly for remote Gateway Interface (CGI), JavaScript, Standard Query access systems in general, as well as instrumentation Language (SQL) and many more, which enable the [5-7]. exchange of variables and the preparation of dynamic As an example, this article describes the remote HTML documents. Figure 1 shows the general control of Rostock University’s ultrasonic, eddy- structure of a http-based remote-controlled experiment current and optical (CCD) research measurement using the graphical programming language LabVIEW equipment using a http-based client-server system and and an integrated http Web server (Internet gateway system, including the online visualisation of Toolkit) [3]. the dynamic runs of real research experiments The server itself has to fulfil two important tasks. Firstly, it controls the experiment. In the actual REMOTE CONTROL CLIENT-SERVER version the control of the experiment works with the SYSTEM graphical elements, the so-called virtual instruments, which were developed using the graphical program- Client-server systems have some advantages com- ming language G (by means of the LabVIEW soft- pared with simple Remote-Access Systems (RAS). ware development environment, National Instruments) They have better security, a higher functionality and [1]. The virtual instruments realise the hardware can be administrated more easily and effectively on access to the experiment: analogue and digital server Client Intranet Browser Connection - Internet - ISDN/DSL Internet Protocol: TCP/IP Firewall Intranet HTTP-Server Remote controlled LAB HTM L-Pages analog/digital I/O-Ports Sensor technique G-Server Intrum entation Bus: - IEE 488.2/IEC 625 - RS 232 Control systems Virtual - U SB Instrum ents (VI) Figure 1: Structure of an http-based remote controlled laboratory or experiment. Client-Server and Gateway Systems... 203 Remote Controlled Experiments VLM 200 HP-GPIB- Software - Components Measurement LAN- Client LSC 5000 Devices Measurement-PC IDE: and HP VEE 5.01/ VEE Pro Software - Components LAN- Server LAN HP I/O Libraries IDE: Program: I/O_ Config HP VEE 5.01/ VEE Pro or higher ◊ LAN - Client Installation HP I/O Libraries Gateway HP VEE - Software: Program: I/O_ Config VLM200_LSC5000. vee ◊ LAN - Server Installation Hostname: Spectrum IP - Address: 193.175.188.155 HP VEE Device I/O - Data: vee . io PC - Cards, AT&PCI KFA - 8I PCI - 20 Software - Components Gateway Software - Components I/O-Driver: kfa8i. dll , kfa8i.h, pci20dll, pci20.h Client HP VEE Service Manager: veesm . exe * eg the LAN - Client HP VEE Remote - Function: init _ Lib . vee Internet Figure 2: Structure of a proprietary client-server system for remote-controlled experiments using VEE. I/O-systems or the standard measurement bus time slot techniques. A software and/or hardware systems such as IEEE 488.2 (GPIB), RS 232 or USB. firewall solution is helpful for these configuration and Secondly, it has to perform its duty as a http server administration problems. at the disposal of requesting clients, which means that the transfer of a requested HTML document, in which REMOTE CONTROL GATEWAY SYSTEM the graphical elements are embedded, is also one of its tasks. The conversion from the graphical elements Gateway technology enables communication between of the virtual instruments of the LabVIEW control pro- a (client) PC and the gateway with instrumentation gram (eg input/output) into the HTML document is bus connectors, such as GPIB or RS232 via a Local performed by a G-server. The G-server is a part of Area Network (LAN). The gateways themselves have the Internet toolkit (National Instruments), which also the structure of a server: the internal server transmits provides virtual instruments for the use of other Internet the data from the LAN to the other bus system (GPIB services, such as the File Transfer Protocol (FTP) or RS232) over layer 3, or higher, of the Open System and e-mail. Interconnection (OSI) references model using Stand- Figure 2 shows the structure of a proprietary cli- ard Instrument Control Library (SICL) software [2]. ent-server system for remote-controlled experiment The SICL software also includes a LAN/GPIB server using the graphical programming language VEE [2]. so that any PC GPIB- interface card could act as a The functionality between client and server can be gateway. The access control could be easily realised extended by means of elements like CGI and Java. by means of a simple IP-list in the Gateway. On Through these technologies, the access rights of the other hand, if a client has the right of access to a clients to stored data from the server, password gateway, then he/she controls everything on the protection and much more can be achieved. These instrumentation bus! include solutions for active task control of IP number Figure 3 shows the general structure of a gate- and/or additional password control for cases where way-based remote-controlled experiment/laboratory more than one client has the right to access the using the graphical programming language VEE PRO remote controlled experiments, using time stamp or [3]. 204 H. Ewald & G.F. Page Figure 3: Structure of a gateway-based remote controlled laboratory. ONLINE VISUALISATION up to four cameras) and videostreaming technology, the requirements on dynamic process visualisation can Online visualisation of the remote control process is be eased; this has increased the success and accept- one of the major problems that have to be solved. In ance of remote controlled experimentation [4]. The the first version of a http client-server system using disadvantage of this solution is that the software for LabVIEW software, a one or two simple CCD the remote controlled camera system must be installed camera system, connected on the server via USB, is at the client side of the system, as well as the server used for the visualisation of the dynamic actions of side.