Installation

Status: published on npm and public, so the npm install @cosyte/mllp command below is live. Where the package sits on the release ladder, and what that means for the stability of its public surface, is stated in one place: API stability. Read it before you pin.

Prerequisites

• Node.js 22 or later. CI runs every pull request on Node.js 22, 24 and 26. The public surface uses Symbol.asyncDispose and AbortSignal, both available on every supported line.
• A package manager: npm, pnpm or yarn.

Install

npm install @cosyte/mllp

The package has no runtime dependencies. The client, the server and the framing codec use Node.js built-ins only (net, tls, events and crypto).

The optional @cosyte/hl7 peer

@cosyte/hl7 is an optional peer dependency, needed only for the @cosyte/mllp/ack-from-hl7 subpath, which builds acknowledgments by parsing the inbound message with it. Everything else (framing, the client, the server, TLS and the in-memory transport) works without it.

npm install @cosyte/hl7

Calling into ack-from-hl7 without the peer installed throws a typed MllpPeerMissingError, not a bare module-not-found error. The peer is loaded on first use, so importing the subpath alone does not need it.

The optional fast-check peer

fast-check is an optional peer dependency too, needed only for the @cosyte/mllp/arbitraries subpath, the generators for property-testing your own code. Install it where your tests run:

npm install --save-dev fast-check

Smoke test

Confirm the package resolves and its version marker is present:

import { VERSION } from "@cosyte/mllp";

typeof VERSION; // => "string"

If that runs, the install is good. Continue with the Quickstart.

Module systems

@cosyte/mllp is an ES module package that also ships a CommonJS build, and each condition carries its own type declarations (.d.ts for import, .d.cts for require), on all four entry points: the root, /testing, /ack-from-hl7 and /arbitraries.

// ES modules and TypeScript
import { MllpClient, MllpServer } from "@cosyte/mllp";

typeof MllpClient; // => "function"
typeof MllpServer; // => "function"

// CommonJS
const { MllpClient, MllpServer } = require("@cosyte/mllp");

Every release is checked with attw (Are the Types Wrong) across the four entry points, so the types an editor shows match the build that loads.