Terminal software

What you call a board with. Any telnet client works, but some are built for this and look a great deal better doing it.

Just tell me what to install

SyncTERM, on Windows, macOS or Linux. It is made for calling boards: it speaks ANSI and CP437 properly, handles file transfers, keeps a dialling directory, and understands telnet:// links so clicking an address on this site actually works. If you install one thing, install this.

On a phone, NetRunner on Android and MuffinTerm on iOS and macOS both do the job and render ANSI art correctly.

The rest of the modern options

ClientPlatformWorth knowing
SyncTERMWindows, macOS, LinuxThe default recommendation. ANSI, CP437, transfers, dialling directory.
NetRunnerWindows, AndroidFrom the Mystic BBS author. Good ANSI.
mTelnetWindowsSmall, fast, built for BBSes.
MuffinTermiOS, macOSHandles PETSCII as well as ANSI.
PuTTYWindowsEverywhere already, but set the character set to CP437 or the art will be wrong. Not built for this.
telnetLinux, macOS, BSDtelnet unleashed.local 6400. Fine and plain. On Debian or Ubuntu: sudo apt -y install inetutils-telnet.
ncanywherenc host 6400. Works, negotiates nothing, and looks it.

macOS removed its telnet command in High Sierra. Install SyncTERM or MuffinTerm rather than fighting it.

Windows has a Telnet Client too, but it is an optional feature that is off by default and it renders ANSI poorly. Use something else.

Whatever you use, remember what you are using it for. Telnet carries every

keystroke in the clear, including your password. Never reuse a password on a

telnet board.

Clicking an address instead of typing it

Every board on the list has its address as a link. Whether that link does anything depends on which program your computer has registered for telnet://, and the default is often wrong or missing. How to fix that.

The address is also plain selectable text on every listing, on purpose, so copy and paste always works no matter what your machine does.

Calling from something older

This is the more interesting half. A board answers anything that can open a telnet session, and with a bridge that includes machines built before the protocol was common.

Commodore

MachineSoftwareOnto the wire
C64, C128CCGMS, Novaterm, DesTerm 128TeensyROM, WiModem232, Comet64, Zimodem, or an RS-232 cartridge
VIC-20, PET, Plus/4period terminal softwarea user-port RS-232 interface to a bridge

The board speaks PETSCII natively, at 40 or 80 columns, and works out which on connect. A C64 gets a C64 screen, not an approximation of one.

Atari

MachineSoftwareOnto the wire
Atari 8-bitBobTerm, Ice-TFujiNet, or an 850 interface to a bridge
Atari ST, FalconUniTerm, CoNnectthe built-in serial port to a bridge

Apple and Amiga

MachineSoftwareOnto the wire
Apple II, IIgsProTERM, ASCII Express, SpectrumUthernet II, or a Super Serial Card to a bridge
Classic MacZTerm, White Knightthe modem or printer port to a bridge
AmigaNComm, term, JR-Commthe serial port to a bridge, or a TCP/IP stack

Everything else

MachineSoftwareOnto the wire
TRS-80 Model 100the built-in TELCOMthe RS-232 port to a bridge
MSXTELNET for UNAPIan ethernet or Wi-Fi UNAPI cartridge
ZX SpectrumVTX 5000, Spectranet clientsa Prism VTX 5000 or a Spectranet card
Amstrad CPCEwenTerma serial interface to a bridge
CP/M, S-100Kermit, MEXthe machine's serial port to a bridge
DOSTelix, Procomm Plus, Qmodem, Terminatea packet driver and a TCP/IP stack, or a serial bridge

Actual terminals

TerminalOnto the wire
DEC VT100, VT220, VT320a terminal server, a USB serial adapter, or the board's own serial bridge
Wyse WY-60, Televideo 925, ADM-3A, Heathkit H19the same
Teletype Model 33 ASRa current loop converter, at 110 baud, if that is the sort of thing you enjoy

What a bridge is

Most of the machines above have a serial port and no idea what TCP is. A bridge sits between the two: it takes the serial line on one side and speaks telnet on the other, so the old machine thinks it is talking to a modem.

Hardware ones for Commodore and Atari are listed above. On anything with a serial port, a Raspberry Pi running tcpser, or an ESP32 running Zimodem, does the same job for a few pounds. A real modem and a real phone line also still work, if you have both.

What the board does with all this

It works out what it is talking to when you connect: ANSI with CP437 or UTF-8, PETSCII at 40 or 80 columns, or plain ASCII, and draws itself accordingly. You do not configure anything. A C64 and a modern laptop can be in the same chat room and both see something that looks right to them.