VT-340 Terminal Emulator

A software emulator of the VT-340 display terminal, written in Object Pascal (FreePascal / Lazarus). Designed for connecting to the BESM-6 mainframe at besm6.cs.msu.ru via Telnet or SSH.

Version: 02.1 (30.05.2024) Authors: Н.В.Макаров-Землянский, А.П.Ильин

What Is This?

The BESM-6 was a Soviet high-performance mainframe computer. A working replica is maintained at Moscow State University and is accessible over the internet. This program provides a period-correct VT-340 terminal interface to that system, including the characteristic hardware buttons (MPON, PERR, ROLL, BLINK, ERASE, SEND, DL, IL, DC, IC) and the НВМЗ keyboard layout used with the machine.

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Features

• Telnet and SSH connections
• Two display styles: Accurate (fixed-width screen buffer) and Modern
• Configurable screen size (16 lines, fixed, or fit-to-window)
• НВМЗ and Windows keyboard layouts
• Ctrl-character display modes (blink, uppercase, space)
• Server list with per-server connection profiles
• Text search in the terminal buffer
• Email (SMTP/IMAP) integration via Indy
• Password-protected startup
• Settings persisted in Prm.ini

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Building on Ubuntu

1. Install build dependencies

sudo apt install fpc

This provides FreePascal 3.2.2 and the Lazarus LCL units (GTK2 widgetset). The Indy networking library is checked out as the Indy/ directory and compiled from source automatically — no separate installation is needed.

2. Clone the repository

git clone <repo-url> vt340
cd vt340

3. Build

make

The compiler auto-detects the Lazarus paths for the standard Ubuntu/Debian package layout. The binary is written to bin/vt340.

Build variants

make DEBUG=1          # Debug build (-g -gl -dDEBUG), no optimisation

make LCLDIR=/path     # Override the LCL units directory (non-standard install)

make clean            # Delete build artefacts (obj/ and bin/)

Cross-compiling to Win32

To produce a bin/vt340.exe from Linux you need a FreePascal cross-compiler targeting i386-win32:

make CROSS=1 FPC=/path/to/i386-win32-fpc LCLDIR=/path/to/win32-lcl-units

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Running

./bin/vt340

On first launch the program creates Prm.ini in the working directory to store all settings.

Note: The Linux build is a native GTK2 application. Some features (printing, certain scroll operations) are Windows-only and are silently disabled on Linux.

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Connecting to the BESM-6

Telnet

1. Open Parameters → Server.
2. Add a server: address besm6.cs.msu.ru, port 23, type Telnet.
3. Click Connect (or press the MPON button).

SSH

SSH tunneling is handled by a bundled plink.exe (PuTTY's command-line client) on Windows. Configure the tunnel parameters under Parameters → SSH: host, port, username, and the path to your .ppk private key file. The application launches plink.exe as a subprocess to create a local TCP tunnel, then connects Telnet to localhost:<tunnel-port>.

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Configuration file — Prm.ini

All settings are stored in INI format next to the executable.

Section	Contents
[Main]	Window position and size
[Server]	Active connection (address, port, type, SSH parameters)
[List Servers]	Saved server profiles
[Screen]	Font, colours, keyboard layout, Ctrl-display mode, password

Delete Prm.ini to reset everything to defaults.

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Documentation

Additional documentation is in the doc/ directory:

• Displaying-on-VT340-BESM4.md — guide to displaying BESM-4 output on a VT-340 terminal (also available as PDF)
• vt340-linux.png — screenshot of the emulator running on Linux

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Project Structure

vt340.dpr               — Program entry point; creates all forms
MainCV.pas              — Global state (connection params, display settings)
WinUnix.pas             — Platform abstraction (TMemo scroll operations)
UFormMain.pas           — Main terminal window
UFormSettingsServer.pas — Server list dialog
UFormSettingSSH.pas     — SSH tunnel configuration
UFormSettingsScreen.pas — Font, colour, keyboard settings
UFormEntry.pas          — Startup password dialog
UFormSetPassword.pas    — Change password dialog
UFormSearch.pas         — Text search in terminal buffer
UFormDebug.pas          — Debug output window
UFormHelp.pas           — Help viewer (also handles email via Indy SMTP/IMAP)
UFormMessage.pas        — Generic message dialog
UFormLanguage.pas       — Language / charset selection
plink.exe               — PuTTY plink for SSH tunneling (Windows)
Prm.ini                 — Runtime settings (created on first run)

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Dependencies

Dependency	How supplied
FreePascal ≥ 3.2	System package (apt install fpc)
Lazarus LCL	Checked out from Github
Indy 10	Checked out from Github
plink.exe	Bundled (Windows SSH tunneling only)