3.1 Comparison of the Three I/O Models

1. Relationship Between Java I/O and System Calls

1.1. I/O Types of System Calls

I/O Models

2. Java I/O Classification

2.1. BIO

Synchronous blocking I/O: a connection to a thread.

On the server side, multiple threads are needed to process multiple client connections and read/write requests. Generally, ServerSocket uses one thread (accepting new connections), and each client Socket uses one thread (read or write).

It belongs to synchronous blocking in the I/O model.

2.2. NIO

Synchronous non-blocking I/O: a request a thread.

On the server side, one thread can process multiple client connections and read/write requests. Generally, a Selector monitors client connections (accepting new connections). Each incoming connection creates a Channel. The Selector polls these Channels, and when an event occurs it is handed to the application for processing (read or write).

It belongs to I/O multiplexing in the I/O model and is implemented using epoll on Linux.

2.3. AIO

Asynchronous non-blocking I/O: a valid request a thread.

On the server side, one thread can process multiple client connections and read/write requests. Compared with NIO, I do not need to poll synchronously. The work is handed to the operating system asynchronously, and I am notified through a callback when processing is complete.

This is an interface standard. An operating system may implement it or may not. Linux does not implement it.

It belongs to asynchronous I/O in the I/O model. It uses epoll on Linux and IOCP on Windows.

3. I/O Comparison

3.1. NIO vs. BIO

	BIO	NIO
	Stream-oriented	Buffer-oriented
	Blocking	Non-blocking (can handle other things)
	None	Selector (one thread can serve multiple Channels)

4. References

• Differences Among BIO, NIO, and AIO (Easy to Understand) - CSDN
• Java BIO, NIO, AIO Understanding