ThinkerQAQ

NOTE

Selector-Based NIO Server

Designing a Java non-blocking server with Selector, per-connection state, partial I/O, and backpressure.

JavaCreated Updated 1 min readhistorical

This is a historical learning note and may contain outdated or incomplete understanding.

A selector-based server typically:

  1. opens a non-blocking ServerSocketChannel;
  2. registers it for accept readiness;
  3. waits in Selector.select();
  4. accepts connections and registers socket channels;
  5. handles read/write readiness using connection-specific state.

Never assume one readable event equals one message. TCP is a byte stream, so decode frames across arbitrary read boundaries.

Write readiness also needs care: keep unsent bytes in a bounded output buffer and register for write interest only while data remains. Otherwise a slow client can turn unbounded application output into a memory problem.