Java Socket编程实例（四）- NIO TCP实践

一、回传协议接口和TCP方式实现：

1.接口：

import java.nio.channels.SelectionKey;
import java.io.IOException;

public interface EchoProtocol {
 void handleAccept(SelectionKey key) throws IOException;
 void handleRead(SelectionKey key) throws IOException;
 void handleWrite(SelectionKey key) throws IOException;
}

2.实现：

import java.nio.channels.*;
import java.nio.ByteBuffer;
import java.io.IOException;

public class TCPEchoSelectorProtocol implements EchoProtocol{
  private int bufSize; // Size of I/O buffer

  public EchoSelectorProtocol(int bufSize) {
    this.bufSize = bufSize;
  }

  public void handleAccept(SelectionKey key) throws IOException {
    SocketChannel clntChan = ((ServerSocketChannel) key.channel()).accept();
    clntChan.configureBlocking(false); // Must be nonblocking to register
    // Register the selector with new channel for read and attach byte buffer
    clntChan.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(bufSize));

  }

  public void handleRead(SelectionKey key) throws IOException {
    // Client socket channel has pending data
    SocketChannel clntChan = (SocketChannel) key.channel();
    ByteBuffer buf = (ByteBuffer) key.attachment();
    long bytesRead = clntChan.read(buf);
    if (bytesRead == -1) { // Did the other end close?
      clntChan.close();
    } else if (bytesRead > 0) {
      // Indicate via key that reading/writing are both of interest now.
      key.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);
    }
  }

  public void handleWrite(SelectionKey key) throws IOException {
    /*
     * Channel is available for writing, and key is valid (i.e., client channel
     * not closed).
     */
    // Retrieve data read earlier
    ByteBuffer buf = (ByteBuffer) key.attachment();
    buf.flip(); // Prepare buffer for writing
    SocketChannel clntChan = (SocketChannel) key.channel();
    clntChan.write(buf);
    if (!buf.hasRemaining()) { // Buffer completely written?
      //Nothing left, so no longer interested in writes
      key.interestOps(SelectionKey.OP_READ);
    }
    buf.compact(); // Make room for more data to be read in
  }

}

二、NIO TCP客户端：

import java.net.InetSocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

public class TCPEchoClientNonblocking {

  public static void main(String args[]) throws Exception {
    String server = "127.0.0.1"; // Server name or IP address
    // Convert input String to bytes using the default charset
    byte[] argument = "0123456789abcdefghijklmnopqrstuvwxyz".getBytes();

    int servPort = 5500;

    // Create channel and set to nonblocking
    SocketChannel clntChan = SocketChannel.open();
    clntChan.configureBlocking(false);

    // Initiate connection to server and repeatedly poll until complete
    if (!clntChan.connect(new InetSocketAddress(server, servPort))) {
      while (!clntChan.finishConnect()) {
        System.out.print("."); // Do something else
      }
    }
    ByteBuffer writeBuf = ByteBuffer.wrap(argument);
    ByteBuffer readBuf = ByteBuffer.allocate(argument.length);
    int totalBytesRcvd = 0; // Total bytes received so far
    int bytesRcvd; // Bytes received in last read
    while (totalBytesRcvd < argument.length) {
      if (writeBuf.hasRemaining()) {
        clntChan.write(writeBuf);
      }
      if ((bytesRcvd = clntChan.read(readBuf)) == -1) {
        throw new SocketException("Connection closed prematurely");
      }
      totalBytesRcvd += bytesRcvd;
      System.out.print("."); // Do something else
    }

    System.out.println("Received: " + // convert to String per default charset
        new String(readBuf.array(), 0, totalBytesRcvd).length());
    clntChan.close();
  }
}

三、NIO TCP服务端：

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.*;
import java.util.Iterator;

public class TCPServerSelector {
  private static final int BUFSIZE = 256; // Buffer size (bytes)
  private static final int TIMEOUT = 3000; // Wait timeout (milliseconds)

  public static void main(String[] args) throws IOException {
    int[] ports = {5500};
    // Create a selector to multiplex listening sockets and connections
    Selector selector = Selector.open();

    // Create listening socket channel for each port and register selector
    for (int port : ports) {
      ServerSocketChannel listnChannel = ServerSocketChannel.open();
      listnChannel.socket().bind(new InetSocketAddress(port));
      listnChannel.configureBlocking(false); // must be nonblocking to register
      // Register selector with channel. The returned key is ignored
      listnChannel.register(selector, SelectionKey.OP_ACCEPT);
    }

    // Create a handler that will implement the protocol
    TCPProtocol protocol = new TCPEchoSelectorProtocol(BUFSIZE);

    while (true) { // Run forever, processing available I/O operations
      // Wait for some channel to be ready (or timeout)
      if (selector.select(TIMEOUT) == 0) { // returns # of ready chans
        System.out.print(".");
        continue;
      }

      // Get iterator on set of keys with I/O to process
      Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
      while (keyIter.hasNext()) {
        SelectionKey key = keyIter.next(); // Key is bit mask
        // Server socket channel has pending connection requests?
        if (key.isAcceptable()) {
          System.out.println("----accept-----");
          protocol.handleAccept(key);
        }
        // Client socket channel has pending data?
        if (key.isReadable()) {
          System.out.println("----read-----");
          protocol.handleRead(key);
        }
        // Client socket channel is available for writing and
        // key is valid (i.e., channel not closed)?
        if (key.isValid() && key.isWritable()) {
          System.out.println("----write-----");
          protocol.handleWrite(key);
        }
        keyIter.remove(); // remove from set of selected keys
      }
    }
  }

}

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