NullModem Reader

English · Deutsch

A native, cross-platform QWK(E) offline reader with automatic packet exchange against NullModem BBS. ANSI art is rendered through the same grid the BBS itself uses.

Dependency

The reader builds on the kit, the foundation it shares with NullModem BBS: ansi (grid, CP437, SGR, layout, templates), qwk (the QWK/QWKE format layer) and zmodem. Server and reader have to agree on file format and screen rendering; two copies of the same code drift apart from the first bug fix on, and with QWK you only notice when someone's mail goes missing.

Packages in the reader

Package	Role
internal/app	The whole interface. Knows neither terminal nor window: keys in, ansi.Grid out
internal/tui	Terminal front end -- paints the grid into tcell cells
internal/gui	Window front end -- paints the same grid with a CP437 bitmap font
internal/exchange	One mail exchange: send, then fetch -- plus the lock that keeps two from running at once
internal/sched	Unattended polling: interval, jitter, backoff
internal/xfer, store, compose, ui, config	Transport, queue and read pointers, composing, grid preparation, configuration

The grid

ansi.Grid is the only representation of screen content; everything else is a blitter over it:

Blitter	Target
ansi.Grid.Encode (from the BBS)	a terminal that speaks CP437 natively (SyncTERM, PuTTY over Telnet)
ansi.ToHTML (from the BBS)	web preview
ui.GridToTerminal	a modern UTF-8 terminal, line by line
tui.present	tcell full screen, cell by cell
gui.paint	a window, CP437 bitmap font via Cell.Char
gui.Rasterize	PNG -- the same picture as the GUI, without a window

Not only the art takes this path but the whole interface: lists, headers, the status bar and the input form are drawn into a grid. A front end is thus a blitter and an input source, not a second copy of the interface -- which is why terminal and window can't drift apart.

The UTF-8 blitter is needed because raw CP437 bytes arrive as mojibake in a UTF-8 terminal. Going through the grid also resolves cursor-addressed art that isn't drawn in character order.

Status

Done and tested

• The QWK/QWKE format layer in both directions -- the BBS only needed to write, the reader needs the reading side too: ReadControlDAT, OpenPacket, ParseQWKEKludges, ReadToReaderEXT, BuildReplyPacket
• Transport against the BBS API: login, download (204 = no new mail), upload, area selection
• Rendering: ANSI art, CP437 prose, ASCII-art detection, header fields
• TUI (tcell): conference list → message list → message, welcome screen, scrolling, help overlay, resize. Tested against tcell's simulation screen, not just looked at by hand.
• Writing replies: r replies (recipient, subject and quote filled in), e writes a new message. You write the text in the built-in editor (see Writing); set $VISUAL/$EDITOR to get your own instead -- key bindings, undo, spell checking. Drafts go into a queue that survives a restart; nmr fetch builds a .REP from it and sends it.
• Read pointers: unread messages are marked •, the conference list shows 3/12 msg, a conference opens at the first unread message, m marks everything read. Kept across sessions and packets.
• GUI (Ebitengine): its own window with an embedded CP437 8×16 font, integer scaling, DOS palette. The same interface as in the terminal, pixel-exact -- block graphics tile seamlessly.
• Windows touches: a program icon (drawn by tools/mkicon from the CP437 font) and version details in nmr.exe, the same icon for the window; held arrow, page and delete keys repeat in the window
• Setup and exchange inside the reader: a setup dialog on first start, f exchanges mail in the background, the password in the system's keychain -- see First start without a command line
• Scheduler: nmr daemon exchanges on a schedule -- an interval per system, jitter against simultaneous access, exponential backoff on failures (capped at one hour), a file lock against double runs.
• The nmr command line: open, gui, init, fetch, daemon, outbox, areas, list, read, screen
• Builds for linux, darwin and windows, amd64 and arm64 each -- all without cgo, so from a single machine (see Releases)

Open

• The kit's zmodem is ready but unused, in case a serial link is ever needed.

Installing

Ready builds are under Releases: one archive per platform with nmr (or nmr.exe), this README, the license and the font license, plus SHA256SUMS to check them (sha256sum -c SHA256SUMS). nmr version shows which version runs.

• Linux: needs glibc (not Alpine/musl) -- Ebitengine loads X11 at run time, without cgo. nmr gui also needs X11 or XWayland and OpenGL; the terminal mode needs neither.

• macOS: the binaries aren't signed. After downloading, run xattr -d com.apple.quarantine nmr once, or Gatekeeper blocks it.

• Windows: double-clicking nmr.exe opens the window. On first start it asks for the BBS address, user name and password, checks the login and fetches the first mail right away. From a command prompt, all the commands below work as well.

  On first start Windows SmartScreen warns ("Windows protected your PC") because nmr.exe is unsigned and new. Either choose "More info" → "Run anyway", or before unpacking right-click the ZIP → Properties → tick "Unblock". Only needed once.

First start without a command line

nmr gui (on Windows also the double-click) and nmr open need no packet as argument: with nothing set up, the setup dialog appears; set up but nothing downloaded yet, the reader fetches mail at once; otherwise it shows all downloaded packets together as one view. What was unread before an exchange stays that way until it's read -- the BBS delivers a message only once.

Writing

Enter in the form opens the built-in editor in the same window: arrows, Home/End, Page Up/Down; paragraphs wrap at the window's edge and at 79 columns when saved. In a reply the quote is already there (without the original's tearline and origin), the cursor below it. Ctrl+Y deletes the whole line -- held down, one after the other, so a quote is trimmed quickly. Ctrl+S puts the message in the queue, Esc asks before discarding. The reader adds the tagline and tearline itself.

An echomail's SEEN-BY and PATH lines (NullModem BBS includes them from 0.26.2) are hidden; S in the message shows them. In a reply, Ctrl+R inserts them as a quote (BT> SEEN-BY: …) -- quoted, because a bare SEEN-BY: line in the text would be taken for real routing by any tosser.

Paste works everywhere with Ctrl+V (Cmd+V on a Mac), multi-line in the editor, the first line in fields. In the window the reader reads the clipboard itself -- directly on Windows, via pbpaste on a Mac, and via wl-paste, xclip or xsel on Linux, whichever is installed. In a terminal, the terminal's own paste works too.

With VISUAL or EDITOR set, the reader uses that editor instead of the built-in one, as before.

Netmail

N writes a new netmail from anywhere; the netmail conference "Personal" is in the list even without mail (NullModem BBS marks it in the packet since 0.26.0). The form asks for a name and an address: an empty address means someone on this BBS, otherwise an FTN address like 2:301/1.5 -- the reader then sends Name@2:301/1.5. Netmail from another system shows its sender in the same form, so a reply finds its way back.

If the BBS refuses a message (unknown recipient, no write access, …), it stays in the queue with the reason (o, marked !) and isn't sent again: e opens it for correction, after which it goes out with the next exchange; d discards it.

Taglines

New messages and replies get a tagline if you like, as ... text right above the tearline (--- NullModem Reader/nmr <version>). The "Tagline" row in the form chooses with ←/→: none, random (space draws another) or a specific one. The choice is the default for the next message.

About 20 taglines are built in. Your own go in taglines.txt next to the configuration file (%APPDATA%\nmr\ on Windows), one per line, # starts a comment; more than 75 characters don't fit on a line and are skipped.

Cleanup is set in the setup dialog under "Keep days" (keep_days in the configuration, per BBS): a packet in which everything is read is deleted after that many days, and so are sent reply packets; the newest packet always stays. 0 keeps everything -- as does a configuration without the entry. A new setup suggests 30 days. Cleanup runs at start and after every exchange, also with nmr fetch and nmr daemon. To change something in the dialog, the password field may stay empty when one is already saved.

Read pointers are tied to the message number. NullModem BBS uses the database ID for it from version 0.25.1, the same in every packet; before that every packet started at 1, so new mail could appear read. Read pointers from that time are dropped once on first start.

Inside the reader, f exchanges mail -- sends replies, fetches new mail, switches to the new packet -- without freezing the window. s opens the setup again, say after a password change. If the BBS refuses the login, the reader takes you there by itself.

The password goes into the system's password store (Windows Credential Manager, macOS Keychain, Secret Service on Linux). Where there is none, the dialog writes it into the configuration file and says so. NMR_PASSWORD_<ID> in the environment still takes precedence.

Or from source: go install github.com/midrei/nullmodem-reader/cmd/nmr@latest.

Releases

DRY_RUN=1 scripts/release.sh v0.2.0   # test and build into dist/, nothing else
GITHUB_TOKEN=… scripts/release.sh v0.2.0    # REMOTE=github if origin isn't GitHub

The script checks that main is clean and in sync with origin and that go.mod has no replace, runs go vet and the tests, builds all six targets with GOWORK=off -- that is, against the kit version in go.mod, not a local checkout -- and packs them with SHA256SUMS. Only then does it set the tag, push it and create the release with the archives on GitHub. GITHUB_TOKEN is a personal access token allowed to write the repository's contents (fine-grained: Contents read/write).

If the reader needs a new kit version, that comes first -- see Releases in the kit's README.

Trying it out

go run ./tools/mkfixture testdata/SAMPLE.QWK
go run ./cmd/nmr open testdata/SAMPLE.QWK     # in the terminal
go run ./cmd/nmr gui  testdata/SAMPLE.QWK     # in its own window

Keys: ↑↓/jk move, Enter opens, Esc/q back, w welcome screen, n/p next/previous message (after a conference's last one back to the list, on the next one with unread mail), space pages and at the end moves on to the next message, r reply, e new message, N new netmail, m mark conference read, o queue, f exchange mail, s setup, ? help, Q quit.

Without full screen:

go run ./cmd/nmr list   testdata/SAMPLE.QWK
go run ./cmd/nmr screen testdata/SAMPLE.QWK
go run ./cmd/nmr read   testdata/SAMPLE.QWK

Against a real BBS:

go run ./cmd/nmr gui           # setup dialog, then the first mail

or with no window at all:

go run ./cmd/nmr init          # writes an example configuration
export NMR_PASSWORD_NULLMDM=…  # the password not in the file
go run ./cmd/nmr fetch
go run ./cmd/nmr open            # all fetched packets together

Automatically in the background, with poll: per system in the configuration:

go run ./cmd/nmr daemon

The daemon exchanges right at start and then at its interval. Running nmr fetch by hand alongside is safe: both take the same lock, the second says so and does nothing.

Found along the way

withQWKEKludges in NullModem BBS wrote TO:/FROM:/SUBJ: into the message text. Those, however, are the labels of the header fields in the QWKE 1.02 specification's example; the kludges themselves are To:, From:, Subject:. No reader true to the specification (MultiMail, NoCarrierMail) would have recognised the old lines -- it would have shown the header fields cut to 25 bytes, and the kludge lines as text on top.

That's fixed in the kit. ParseQWKEKludges still accepts both spellings when reading, so packets from older NullModem versions stay readable.

Second, EncodeCP437 silently replaced everything unknown with ?. A Mac keyboard produces typographic quotes, dashes and ellipses by itself -- they became question marks without anyone noticing. Now the function transliterates them to ASCII, and EncodeCP437Report names what really couldn't be carried over.

Font

The GUI embeds a CP437 8×16 bitmap font made from Spleen (BSD-2-Clause, copyright Frederic Cambus -- license text in assets/font/LICENSE.spleen). tools/mkfont turns Spleen's CP437 BDF into the flat VGA ROM format, so it stays traceable where the 4096 bytes come from:

go run ./tools/mkfont spleen-8x16-ibm-437.bdf assets/font/cp437-8x16.bin

An outline font wouldn't do here: block graphics must tile seamlessly at every scale, and only a bitmap font with integer scaling can promise that.

License

MIT -- see LICENSE. The embedded Spleen font is under BSD-2-Clause (assets/font/LICENSE.spleen); both licenses are in every release archive.