RetroModem BridgeDial back in Download v3.6
New in v3.6: IRC, ANSI Art Library, plugins & a new look

Put your vintage computer back online.

RetroModem Bridge turns a Windows PC into the modem your old computer always wanted. Type ATDT on your CoCo, Commodore, Apple II, Atari or any serial terminal and connect to real Telnet BBSes, a built-in local BBS, door games, ANSI art and IRC chat. No phone line or modem needed.

Download free for Windows Tour the local BBS
Free & open source (MIT) 66 MB ZIP · no installer Windows 10/11 x64 Real hardware, not just emulators

🔌 No serial port on your PC? Grab the USB serial adapter we recommend or find the cable for your computer →

RetroModem Bridge v3.6 main window: modem lights, serial port and network listener settings, BBS directory with Dark Realms and CoCoNet, and the live log.
Works with serial-capable machines
Tandy CoCo 1/2/3TRS-80Commodore 64/128 Apple IIAtari 8-bit & STAmiga DOS PCsCP/MFujiNet devices
How it works

Your old computer thinks it's dialing a modem.

Nothing changes on the vintage side. Use the terminal program you already know. RetroModem Bridge handles the internet on the Windows side.

01 / VINTAGE COMPUTER

Type a dial command

Your terminal program sends Hayes-style AT commands over the serial port, just like it did in 1989.

ATDT COCO
02 / RETROMODEM BRIDGE

The bridge answers

RMB listens on your COM port (or over Wi-Fi for FujiNet), looks up the alias and opens the connection.

SERIAL ⇄ TELNET
03 / DESTINATION

You're online

Land on a Telnet BBS, the built-in local BBS, a door game, the ANSI art library or IRC.

CONNECT 19200
What you need

One adapter and the right cable.

Modern PCs don't have serial ports. A USB serial adapter gives RetroModem Bridge a COM port, and a null-modem cable connects it to your vintage computer.

Our pick
Step 1 · on the Windows PC

USB to RS-232 serial adapter

The one part every serial setup needs. Plug it into your PC, choose its COM port in RetroModem Bridge, and you're ready to dial.

Check price on Amazon
Step 2 · most machines

Null-modem cable

Connects two "computers" by crossing the send and receive lines. DB-9 female-to-female fits most adapters.

Find on Amazon
Step 3 · if needed

DB-25 adapter & gender changers

Many vintage machines have 25-pin ports. A small adapter kit covers almost any combination.

Find on Amazon

Not sure what fits? Pick your computer.

Our hardware guide lists the exact port, cable, speed and terminal software for each machine.

Tandy CoCoBit-banger or RS-232 Pak TRS-80 / Model 100DB-25 RS-232 Commodore 64/128User-port interface Apple IISuper Serial Card, IIc, IIgs Atari 8-bit850 Interface or FujiNet Atari STDB-25 modem port AmigaDB-25 serial port IBM PC & DOSDB-9 / DB-25 COM port Classic MacMini-DIN-8 modem port CP/M, TI-99, MSX…Everything else

As an Amazon Associate I earn from qualifying purchases. Buying through these links supports RetroModem Bridge at no extra cost to you.

New in v3.6

The biggest RetroModem Bridge release yet.

A plugin system, two new plugins you can dial from your vintage computer, and a completely redesigned Windows app.

RetroModem IRC Client connection screen on an 80x24 terminal, showing Libera.Chat with TLS on.
Plugin · ATDT IRC

IRC from your vintage computer

A full-screen 80×24 IRC client with TLS, channels, private queries, /ME, /WHOIS and unread markers. Libera.Chat is set up out of the box.

The ANSI artwork City of Chaos by ACiD displayed in the RetroModem Bridge ANSI Art Library.
Plugin · ATDT ANSI

ANSI Art Library

Browse decades of scene artpacks from the textfiles.com archive, plus your own local collection. Pause, replay and page through the art on real hardware.

RMB Plugins window listing the ANSI Art Library and IRC Client plugins with their settings.
Plugin API 1

Plugin system

New services drop into a Plugins folder and show up in the local BBS menu with their own dial aliases. Enable, disable and configure them in the Plugin Manager.

Session Mirror showing the local BBS menu followed by NO CARRIER after pressing Hang up.
Windows app

New dark UI & Hang up

Live modem lights, a call status, a Favorites tab and a one-click Hang up that drops the call and sends NO CARRIER, just like a real modem.

The local BBS · ATDT MENU

A whole BBS lives inside the bridge.

Dial ATDT MENU and your vintage computer gets its own ANSI home base. Find boards, dial them, play doors, look at art and chat, all without touching the Windows keyboard.

RetroModem Bridge local BBS main menu with 13 options including BBS directory, door games, ANSI Art Library and IRC Client.
ATDT MENU

These are real, unedited screens from RetroModem Bridge v3.6. The frame is only decoration.

Dial real boards

Hundreds of BBSes are still online. Go call one.

Save a board with a short alias and dial it like it's 1992. RetroModem Bridge handles Telnet negotiation, keeps the connection clean for your terminal, and tracks which boards are up.

RMB> ATDT COCO
CONNECT 19200
… CoCoNet login screen …
RMB> ATH
NO CARRIER
  • Dial by alias (ATDT DARK) or by host and port (ATDT bbs.example.com:23)
  • Test boards with one click and see status, response time and last check
  • Import the Telnet BBS Guide, with monthly and daily updates
CoCoNet BBS login screen with the colorful CoCo logo, dialed through RetroModem Bridge.
ATDT COCO · CoCoNet
Real hardware

Built and tested on a real Tandy Color Computer 3.

RetroModem Bridge is developed against real vintage machines on a real serial cable, not just emulators. The 80-column local BBS, the ANSI renderer and the door game paging are all tuned for actual CRTs.

  • Retro Computer Profiles store each machine's port, baud, DTR/RTS and Telnet settings
  • First-time setup checklist catches the usual COM port and baud rate mistakes
  • Session Mirror shows exactly what your vintage screen is receiving
Tandy CoCo 3 and monitor displaying colorful ANSI art received through RetroModem Bridge.
CoCo 3 CRT showing the Usurper Reborn title screen launched as a local door game.
Usurper Reborn, launched with ATDT USURPER.
Everything it does

Much more than a serial bridge.

RetroModem Bridge started as a TCPSer-style bridge. Today it's a whole connection center for your vintage computer.

AT

Hayes-style modem bridge

The core job, done properly.

  • Pick any COM port and baud rate. A rescan button picks up newly plugged-in USB adapters.
  • AT, ATI, AT&V, ATDT, ATDL redial and ATH hang-up
  • Dial aliases, numbered entries or any host:port
  • DTR, RTS, Echo and Telnet filter controls
  • Live modem lights (DTR, RTS, CTS, DSR, DCD, RX, TX, ONLINE)
  • Per-connection traffic counters and a live, saveable log
N:

FujiNet network listener

No serial cable? Connect over your network.

  • Built-in TCP listener (Telnet or raw TCP), default port 2323
  • UDP auto-discovery on port 2324, so FujiNet clients can find the bridge
  • One-click copy of the ready-made N:TELNET://your-pc:2323/ URL
  • Shows client status and traffic in the Network Listener card
  • Runs alongside the serial bridge, or on its own
≡

Local ANSI BBS

Use everything from the vintage keyboard.

  • ATDT MENU opens a 13-option, 80-column ANSI menu
  • My BBS Directory, Browse BBS Directory, Favorites and Dial History
  • Featured, Random and Online-tested lists
  • News, Time and Help services
  • Page, search and dial numbered entries without retyping hostnames
  • Update the BBS guide from the retro side with ATDT UPDATE
★

BBS directory & guide

Find boards, keep the good ones.

  • Bundled Telnet BBS Guide with 1,000+ boards; monthly, daily or ZIP/CSV updates
  • Import without duplicates; filter by software and "new only"
  • BBS Directory, Favorites and Door Games tabs with live counts
  • One-click Test and Test All Favorites with status and ping times
  • Copy a ready-to-type ATDT command for any entry
  • Import, export and edit entries with notes, category and system type
#

IRC Client plugin

ATDT IRC or ATDT CHAT

  • Classic full-screen 80×24 interface with channels, queries and unread markers
  • TLS on by default, IPv4 and IPv6, with normal certificate checks
  • /JOIN, /MSG, /ME, /WHOIS, /NAMES, /TOPIC, /1–/9 window switching
  • Incoming chat is cleaned so nobody can inject ANSI codes into your terminal
  • Server, nick and channel defaults are saved in the Plugin Manager
▓

ANSI Art Library plugin

ATDT ANSI, ART or ANSILIB

  • Browse artscene.textfiles.com artpacks by year, pack and file
  • Add your own .ANS files or artpack ZIPs to a local folder
  • Downloads only what you open, and caches it for offline viewing
  • Streams art in chunks: P pauses, S stops, R replays, I shows SAUCE info
⚔

Local door games

Dial a game like it's on a BBS.

  • Give any compatible Windows door an alias, such as ATDT USURPER
  • DOOR32.SYS written automatically, with configurable launch arguments
  • Single-key input assist for Y/N and "press any key" prompts
  • Optional "More" paging for long text, with B to page back
Door Game Mode is experimental. How well it works depends on the door program.
▣

Windows app & tools

A control panel you'll actually like.

  • New dark UI with a call status, Start/Stop and one-click Hang up
  • Session Mirror: watch the 80-column session, and optionally type into it
  • Built-in ANSI terminal for testing a board from Windows
  • Retro Computer Profiles and a first-time setup checklist
  • Plugin Manager to enable, disable and configure plugins
  • Support bundle export for easy troubleshooting
Screenshots

The Windows side, redesigned.

Every screenshot is from the v3.6 build. Click any one to see it full size.

Main windowSerial port, network listener and session on the left. Your directory, favorites and doors in the middle, with the live log underneath.
Session MirrorSee exactly what your vintage screen sees, and type into the session from Windows when you need to.
BBS Guide importPick boards from 1,000+ Telnet BBS Guide entries, filtered by software or new boards only.
Door Games tabLocal doors live in their own tab.
Door editorAlias, launch arguments, input assist and paging.
Plugin ManagerTurn plugins on or off and set them up.
Retro Computer ProfilesSave the right serial settings for each machine and switch with one click.
Hang upDrop any call from Windows. Your vintage computer gets a proper NO CARRIER.
Command reference

Everything you can type on the vintage side.

You only really need ATDT MENU. The direct commands are shortcuts for when you know where you're going.

Modem
ATIs the modem there? Replies OK.
ATIBridge identification and features.
AT&VCurrent settings and directory counts.
ATDT ALIASDial a saved BBS or door by alias.
ATDT HOST:PORTDial any Telnet host directly.
ATDL · ATHRedial the last number · hang up.
Local services
ATDT MENUThe local BBS main menu.
ATDT BBSLISTYour saved BBS directory.
ATDT FAVORITESYour favorite boards.
ATDT GUIDE · IMPORTBrowse the Telnet BBS Guide.
ATDT UPDATEDownload the latest guide.
ATDT DOORSLocal door games.
ATDT FEATURED · RANDOMFeatured boards or a random pick.
ATDT ONLINEBoards that passed a connection test.
ATDT NEWS · TIME · HELPBulletin, clock and command help.
Plugins
ATDT ANSI · ART · ANSILIBANSI Art Library.
ATDT IRC · CHATIRC client.
/SERVER /NICK /CONNECTSet up IRC, then connect.
Inside lists: 01–15 dial or view N next pageP previous S searchC clear search M main menuQ disconnect
Get started

From serial cable to BBS in four steps.

Connect the cable, choose a port, start the bridge, dial.

Your vintage computer

  • A serial port or RS-232 interface (or a FujiNet)
  • Terminal software that can send AT commands
  • Any baud rate your hardware supports

Your Windows PC

  • Windows 10 or 11, 64-bit
  • A COM port or a USB serial adapter
  • An internet connection for BBSes and IRC

Example: CoCo 3

  • Deluxe RS-232 Pak or compatible serial interface
  • NetMate or a similar terminal program
  • Null-modem cable to a USB serial adapter at 19200 baud

Download & unzip

Extract RetroModem Bridge to any writable folder and run it. There's no installer.

Pick your port

Choose the COM port and the baud rate your vintage terminal uses, or load a saved profile.

Start the bridge

Click Start Bridge. The modem lights come on when your computer talks to it.

Dial

On the vintage computer, type ATDT MENU. Welcome home.

Need a USB serial adapter or the right cable?

Grab the adapter we recommend, or look up your computer in the hardware guide.

Check price on Amazon
FAQ

Questions people ask first.

Do I need a modem or a phone line?

No. RetroModem Bridge is the modem. Your vintage computer talks to it over a serial cable (or the network, for FujiNet), and the Windows PC uses its normal internet connection.

What cable do I need?

Usually a USB serial adapter for the PC plus a null-modem cable for your vintage computer. Some machines, like the Commodore 64, also need an interface. The hardware guide lists the parts for each computer.

Is it really free?

Yes. RetroModem Bridge is open source under the MIT license, and the full source code is on GitHub.

Which computers work?

Anything with a serial port and a terminal program that can send AT commands: Tandy CoCo and TRS-80, Commodore, Apple II, Atari, Amiga, DOS and CP/M machines, vintage laptops and more. FujiNet-equipped machines can connect over the network listener.

Does the local BBS need the internet?

No. The menu, your directory, favorites, help, time, news, door games and local ANSI art all work offline. Telnet BBSes, IRC, online artpacks and guide updates need an internet connection.

Do I need to install .NET?

The release build is a self-contained Windows x64 app, so you don't need to install anything else.

Why does Windows Firewall ask for permission?

Only if you turn on the network listener, which accepts connections from FujiNet devices on your local network. The serial bridge on its own doesn't need any incoming connections.

Can I add my own ANSI art?

Yes. Put .ANS files or artpack ZIPs in the local ANSI art folder (it defaults to Documents\RetroModemBridge\ANSI Art) and they show up under LOCAL in the ANSI Art Library. You can change the folder in the Plugin Manager.

How do I hang up?

Log off the BBS as usual, press Q in the local menus, or click Hang up in the Windows app at any time. Your computer gets a proper NO CARRIER.

READY.

Your vintage computer has been offline long enough.

Download RetroModem Bridge, plug in the serial cable and type ATDT MENU. The BBS scene is still out there.

Download RetroModem Bridge v3.6 View source on GitHub