Nchan is a scalable, flexible pub/sub server for the modern web, built as a module for the Nginx web server. It can be configured as a standalone server, or as a shim between your application and hundreds, thousands, or millions of live subscribers. It can buffer messages in memory, on-disk, or via Redis. All connections are handled asynchronously and distributed among any number of worker processes. It can also scale to many Nginx servers with Redis. Messages are published to channels with HTTP POST requests or Websocket, and subscribed also through Websocket, long-polling, EventSource (SSE), old-fashioned interval polling, and more.