Nchan Pub/Sub Message Server

This is a repackaged open source software product wherein additional charges apply for cloudimg support services.

## Nchan - Production-Ready Publish and Subscribe Message Server AMI

Nchan is an open source publish and subscribe server built as a module for nginx. Your application publishes a message to a named channel with an ordinary HTTP POST, and Nchan delivers it immediately to every connected client over WebSocket, EventSource (Server-Sent Events), or long polling - whichever the client requests. Because the delivery layer is nginx itself, a single instance holds a very large number of idle connections while your application never maintains a persistent real-time socket.

This AMI delivers a complete, working message server within minutes of launch - not a module you still have to compile and configure.

## Who This Is For

• Teams building live dashboards, notifications, activity feeds, or chat
• Developers adding collaborative editing or job-progress updates to existing apps
• Anyone who needs to push data to browsers or mobile clients without polling
• Organizations that want pub/sub without managing Redis clusters or external brokers

## Why This AMI Over a Manual Install

Instant time-to-value: A wired-up, hardened pub/sub server the moment the instance boots. No source build, no module/ABI juggling, no per-location configuration required.

Secure where the software is not: Nchan endpoints are unauthenticated by default, meaning an open publisher lets anyone inject messages into any channel and an open subscriber leaks every message. This image puts both endpoints behind a credential generated uniquely on each instance's first boot - never baked into the image - so no two instances share one. The statistics endpoint is restricted to loopback only.

Proven, not merely listening: A bundled self-test command publishes a message and confirms delivery across all three transports, so you can verify end-to-end function at any time.

## Application Stack

• nginx (BSD-2-Clause) as the front door on port 80
• Nchan dynamic module (libnginx-mod-nchan 1.3.6, MIT) loaded into nginx and pinned to the distribution nginx ABI
• In-memory memstore for channel storage (no external Redis required for single-instance use)
• Dependency-free WebSocket subscriber and shipped self-test proving publish/receive across all three transports
• First-boot systemd oneshot that mints a per-instance credential, resolves the public IP, and writes a root-only instance info file

## Preconfigured Defaults

• One hundred messages retained per channel for up to one hour
• Late-connecting subscribers receive the full buffered backlog
• Publisher endpoint, subscriber endpoint (all three transports), loopback statistics endpoint, and health endpoint ready immediately

## Security Posture

• No baked credential: htpasswd generated per instance on first boot; both endpoints fail closed until it exists
• Both endpoints authenticated: publisher and subscriber sit behind nginx basic-auth by default
• Statistics restricted: nchan_stub_status bound to loopback only - channel names and subscriber counts never exposed externally
• Nothing pinned or held back: nginx and Nchan are standard distribution packages; ordinary security updates keep them current

## Deployment Quickstart

1. Launch the AMI on an m5.large or larger EC2 instance

2. Open port 80 in your security group (and port 22 for SSH)

3. SSH in and read /root/nchan-info.txt for this instance's publisher credential and endpoints

4. Publish a message: POST http://your-instance-ip/pub/channel-name with basic auth

5. Subscribe over WebSocket, EventSource, or long polling: GET http://your-instance-ip/sub/channel-name with basic auth

6. Run sudo /usr/local/sbin/nchan-selftest to confirm end-to-end delivery

## Get Started Quickly

Need help integrating TLS termination, replacing basic-auth with your application's authorization layer, or tuning retention for your workload? cloudimg support is available 24/7 to help you go from launch to production as quickly as possible.

## About Nchan Upstream

Nchan is a mature, actively maintained project. The most recent upstream release is version 1.3.8 (February 2026), following version 1.3.7 (September 2024). This AMI ships version 1.3.6 as packaged and security-maintained by the underlying Linux distribution.

## About cloudimg

cloudimg publishes and maintains production-ready images across AWS and Azure Marketplace, built from a hardened, fully patched base and backed by 24/7 engineering support.

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