The TELSTAR Videotex System

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Telstar being accessed using BBC Basic for SDL
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TELSTAR accessed using Hearsay on Risc OS5

The TELSTAR videotex system, developed in 2018, is a modern application that provides a simple viewdata/videotext platform similar to those that were prevelant during the 1980s such as Prestel (https://en.wikipedia.org/wiki/Prestel).

The aim of the system is to provide a Viewdata experience for anyone who is interested in how things 'used to be'. Services in the past typically provided access via the public switched telephone network (PSTN) connection, however, Telstar makes use of a simple internet connection. Three Telstar servers currently operate from Digital Ocean's data centre in London and can be accessed using either a Telnet modem in conjunction with a home computer or from a PC/Mobile device using Richard T Russell's BBC Basic for SDL 2.0 example (see below).

For a full up to date list of content available through Telstar, please se the TELSTAR Directory.

TELSTAR is written in Python 3 and it is hosted on Digital Ocean cloud based servers in the London data centre. Each 'live' server can handle many concurrent connections. The host OS is Linux and all TELSTAR services are managed by systemd.

Connecting and Using the Service

BBC Micro, Apple II and other Vintage Systems

The service can be accessed using a vintage computer such as the BBC Microcomputer, Apple II (II+///e etc), Torch or Archimedes using an #Internet Modem, see below.

A vintage home computer requires suitable videotext software. Software designed for use with Prestel will usually work with Telstar, packages are available for the BBC Micro such as Commstar, Anteloper for the Apple II/II+ or Gazelle for the later Apple II machines. Other software packages produced in the 1980-90s exist for other systems. Ideally the software should be configured as follows

   Baud Rate:   2400
   Parity:      None
   Word Length: 8
   Stop Bits:   1


Each internet modem will have its own method for connecting to an IP Address and Port combination, Telstar is listening on the following endpoints.

There are three instances of the TELSTAR service, these are named 'CURRER', ELLIS' and 'ACTON' respectively, see the article Telstar: What's in a Name. The first two are identical and are available at the following addresses.

   Url:  glasstty.com
   Port: 6502
   Url:  glasstty.com
   Port: 6503

The third service is used to test new features and may be subject to short periods of interruption.

   Url:  glasstty.com
   Port: 6504

Please Note that these endpoints are not Telnet Servers nor Web Servers, they are simply TCP listeners that support the videotex application protocol.

RiscOS 5

Telstar can be accessed using RiscOS on modern hardware, such as a Raspberry Pi, using software written by David Pilling called Hearsay II (https://www.davidpilling.com/hearsay.html), see screenshot below right. This package has been updated to include direct TCP connections. This allows the software to be connected directly to Telstar by simply entering glasstty.com, 6503 when prompted. Naturally this will require a DNS server to have been configured within RiscOS. Alternatively the IP address of glasstty.com can be used.

Windows, Linux, Mac OS-X, IOS, Android and Raspberry Pi

To experience Telstar properly it needs to be accessed by an early microcomputer for the videotex era. However, there are several methods of accessing the service using modern devices.

Richard T Russell has written BBC BASIC for SDL 2.0 (https://www.bbcbasic.co.uk/bbcsdl/) which is available for desktop (Windows, Linux, Mac OS-X, Raspberry Pi) and mobile devices (Android/IOS). This product includes a Telstar client within the General section of the included examples.

Matrix Brandy is a fork of Brandy Basic, a BBC Basic V interpreter written by David Daniels and distributed under the GNU General Public Licence Version 2. It was Developed on a CentOS 6 32-bit machine, tested on both CentOS 6 64-bit and a Raspberry Pi. Matrix Brandy BASIC V for Linux with SDL can be found here (http://brandy.matrixnetwork.co.uk/), it includes a 'Telstar' client compiled as a Windows executable http://brandy.matrixnetwork.co.uk/testing/telstar.zip.

Internet Modem

The service can be accessed using an internet modem such as the Arduino based device described in the article Building an Arduino Based TELSTAR Modem. Alternatively, for a Wifi based solution, see Daniel Jamesons article (http://www.amibay.com/showthread.php?99878-WiFi-retro-Modem-for-under-a-tenner) or consider a WiModem232 (https://www.cbmstuff.com/proddetail.php?prod=WiModem232OLED).

For a better experience using one of these modems, please see the article Using an Internet Modem For Telstar and the section #Telstar is not Telnet

Telstar is not Telnet

Whilst TELSTAR is accessed using TCP/IP it is not a Telnet Server. However, TELSTAR does include a Telnet parser which will respond to a very small subset of Telnet negotiation requests.

When a client first connects, TELSTAR attempts a simple negotiation with the client to establish two protocol settings;

  • to ask the client to not use line mode;
  • to indicate that the server will echo any characters received,

Non-Telnet clients can safely ignore this negotiation request completely.

Baud Rate

TELSTAR is designed to operate at 2400 baud when accessed by non-Telnet clients (see below), this speed is set at the server. Throttling the server responses in this way means that any key presses detected during transmission of a frame can successfully cancel the rendering process and allow a user to move to the newly selected frame. In addition the throttling will help prevent modem buffers from overflowing.

If TELSTAR detects a connection from a Telnet type client, baud rate throttling is removed and the system operates at full network speed.

Content

For a full list of the content available please see the TELSTAR Directory. This is currently a 'work in progress' and will be expanded as the content is developed.

There are four main sources of content, these are described below.

Auto-Generated Content

Currently the system takes several live feeds from the BBC, Reuters, Daily Mail, Express, Stardot.co.uk and others. This provides current and automatically updated news and financial information as well as information relating to arts, culture, sport etc. The data is typically refreshed every 10 minutes.

Static Content

Some static content is provided, this includes index and routing frames as well as those encoded frames used for Telesoftware.

API Content

Some content is created by accessing external APIs. For example, the Weather service accesses the OpenWeatherMap API.

Gateway Content

Telstar has a simple gateway facility that allows content from other systems to be presented within Telstar, one such source is the Colossal Cave Adventure game. The adventure game is actually run on a separate server to that of Telstar with the interactive content passing through the gateway service.

Routing

Routing is loosly based on the Prestel system, where navigation can take place by following the menu system, additionally, direct access to a page can be gained by using the special combination shown below.

   *<page number>#
       
       e.g. *890#

Some special combinations allow for pages to be redisplayed of for navigation to a previous page as follows;

   *00 Re-display current frame.
   *09 Re-diaplay current frame (included for compatibility).
   *#  Navigate to the previous page.


Routing by default follows the pure approach, e.g. if the user is viewing page 2 and selects a 1, page 21 will be shown. This is not always appropriate therefore, a Routing Map dictionary is implemented. In cases where the pure routing method is inappropriate e.g. in the above example where pressing 1 should route to page 800 the Routing Map will define this. This means that when following the menu selections pages, data from different information providers can be displayed. This mimics the original Prestel Cross Referencing service and allows full interlinking of content.

Prestel used to have a three frame history allowing the special sequence *# to move back up to three frames. Telstar has an unlimited history. All other special sequences used by Prestel are supported.

Telesoftware

The protocol used for Telesoftware is described in the document File:Prestel Telesoft Protocol Low Res.pdf.

The provided TEST program is a tokenised BBC BASIC program aimed at providing a simple mechanism for users to test their respective client systems.

More software will be published as it becomes available.

Copyrights and Trade Marks

It is the aim of TELSTAR to respect all copyrights and trade maeks. Please let me know if you are affected by any software and content that is published on the system or this site.

Gateway Facilities

TELSTAR features a full duplex 'proxy' Gateway to other viewdata. At the time of writing it is possible to 'gateway' to CCL4 (Tetrachloromethane), NXTEL, and the test version of TELSTAR. In addition, it is also possible to access some none viewdata systems, see #Colossal Cave Adventure below.

Colossal Cave Adventure

TELSTAR, via its #Gateway Facilities can now access the famous 360 point version of Colossal Cave Adventure.

Colossal Cave Adventure (also known as ADVENT, Colossal Cave, or Adventure) is a text adventure game, developed originally in 1976, by Will Crowther for the PDP-10 mainframe. The game was expanded upon in 1977, with help from Don Woods.

Response Frames

TELSTAR includes the facility to present forms to the user requesting input. The frames are referred to as response frames. The first use of this functionality was for the city/town/region search facility for the weather service.

Response Frames are defined as standard Frame but include a collection of Fields. The fields include field validation and rendering information and are passed to a Response Processor when submitted by the user. The Response Processor handles the users request (e.g. get weather info) and generates temporary in-memory frames to display the results.

Meta-Data

Telstar sends meta-data in a short text response just prior to the first frame being sent and allows clients to automatically update system clocks etc. The meta-data (UTC Date and time only at the moment) sits between the first character 0x0C and a subsequent 0x0C. The char 0x0C is a clear screen character which means that normal users of the system will not see this data, however, clients will.

The first data received from Telstar will look something like the following:

   \x0c20180720T1005Z\x0c ...

The date and time in UTC is shown as follows 20180720T1007Z, meaning 10:05, 20 July 2018 UTC.

PLEASE NOTE, this is only appears on the initial page (page 99), however this page can be re-displayed at anytime by accessing page *99#.

Screen Roll Over

Videotex clients do not normally scroll. When the cursor is positioned below the bottom row it appears on the top row, similarly a cursor that is moved up from the top row will appear on the bottom row. The same is true for left and right cursor movements. In line with historic videotex services, Telstar uses this behaviour to calculate the shortest path when positioning the cursor. For example if a status message is to be displayed on the bottom row, and the cursor is currently on the top row, Telstar will move the cursor up as this is the shortest route to the bottom row. For developers creating videotex clients, this will need to be taken into account.

The Database

TELSTAR does not make use of a database engine. All static Frame objects are created from the TELSTAR GIT source repository at the time of deployment and stored as pickled Frame objects. During deployment, the dynamic content frames are built and stored in the same way as the static frames, however, these frames are re-created every 20 minutes in order to update the content.

The Routing Map is also defined within the TELSTAR GIT source repository and is loaded into memory when the TELSTAR service starts.

Acknoledgements

Weather Services

Artwork

Technical Help

References

  • [1] Fedida, S. & Malik, R. (1979) The Viewdata Revolution Associated Business Press
  • [2] Martin, J. (1982) Viewdata and the Information Society Prentice Hall
  • [3] Money, S.A. (1979) Teletext and Viewdata Newnes
  • [4] Stokes, A. (1980) Viewdata: a public information utility (2nd Ed.)
  • [5] Council for Educational Training (CET) (1986) Format Recommendations for Prestel Telesoftware CET

See Also