Java NIO and TCP Connections

Internal

• TCP
• Java Non-Blocking I/O Concepts

Overview

This article describes the programming model involved in establishing a simple TCP connection and interacting with it with non-blocking I/O, from Java. We use Java NIO APIs primitives introduced in Java 4.

Programming Model

Server

The server code uses a Selector to multiplex over selectable channels: selectable channels: a ServerSocketChannel that listens for incoming network connections and creates new SocketChannels for each new TCP connection, and subsequently registered SocketChannels.

//
// Main selector multiplexor. We use the main thread as selector thread.
//

Selector selector = Selector.open();

//
// The ServerSocketChannel used to accept new TCP connections
//

ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
InetSocketAddress address = new InetSocketAddress(PORT);
ServerSocket ss = serverSocketChannel.socket();
ss.bind(address);

//
// Register the ServerSocketChannel with the selector
//

serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

The main event loop handles two types of events: new connections and data availability on the existing connections. Once a new connection is detected, the selector thread retrieves the corresponding SocketChannel and registers it with the same selector. If data becomes available on any of the registered SocketChannels, we use a Buffer to read it.

        //
        // The main event loop
        //

Client

Example

Playground Java NIO and TCP Connections