如何使用套接字通道读取和写入数据并接受连接
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【中文标题】如何使用套接字通道读取和写入数据并接受连接【英文标题】：how to read and write data and accepting connection using socket channel 【发布时间】：2010-10-28 16:38:11 【问题描述】：我使用 java NIO 创建了一个简单的服务器客户端应用程序。 我在那里使用了一个选择器来接受连接、读取数据和写入。 但我想要一个应用程序，其中 1 个选择器将忙于接受连接，而第 2 个选择器将读取数据，而第 3 个选择器将写入数据。
意味着我不想将所有负载都放在单个选择器中。
如何做到这一点？ 有没有在线帮助
谢谢 迪帕克。
// 创建选择器 选择器选择器 = Selector.open();
// Create two non-blocking server sockets on 80 and 81
ServerSocketChannel ssChannel1 = ServerSocketChannel.open();
ssChannel1.configureBlocking(false);
ssChannel1.socket().bind(new InetSocketAddress(80));
// Register both channels with selector
ssChannel1.register(selector, SelectionKey.OP_ACCEPT);
while (true)
// Wait for an event
selector.select();
// Get list of selection keys with pending events
Iterator it = selector.selectedKeys().iterator();
// Process each key
while (it.hasNext())
// Get the selection key
SelectionKey selKey = (SelectionKey)it.next();
// Remove it from the list to indicate that it is being processed
it.remove();
// Check if it's a connection request
if (selKey.isAcceptable())
// Get channel with connection request
ServerSocketChannel ssChannel = (ServerSocketChannel)selKey.channel();
// Accepting a Connection on a ServerSocketChannel
SocketChannel sChannel = serverSocketChannel.accept();
// If serverSocketChannel is non-blocking, sChannel may be null
if (sChannel == null)
// There were no pending connection requests; try again later.
// To be notified of connection requests,
else
// Use the socket channel to communicate with the client
【问题讨论】：
我能问一下您为什么要尝试这种设计吗？您希望从中获得什么？ 实际上它使我的表现不佳。 【参考方案1】：可以使用register(Selector sel, int ops) 注册具有多个选择器的通道。然后在每个选择器上注册不同的兴趣操作：
// After the accepting a connection:
SelectionKey readKey = sChannel.register(readSelector, SelectionKey.OP_READ);
// When you have something to write:
SelectionKey writeKey = sChannel.register(writeSelector, SelectionKey.OP_WRITE);
【讨论】：
不，因为这通常不是你这样做的方式。我假设您已经查看了rox-xmlrpc.sourceforge.net/niotut 以了解基本的 NIO 处理。您还可以查看各种 NIO 实现。我在naga.googlecode.com 的代码可以免费复制或使用。【参考方案2】：通常，在非阻塞 tcp 服务器上，先接受，然后读取，然后写入，
您需要按此顺序注册选择器才有意义。
示例代码
这是一个非阻塞io的完整示例：
TcpChannelTest.java：（一个TestNG测试类）
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.Set;
import org.testng.annotations.Test;
/**
* tcp channel test
*
* @author eric
* @date Sep 2, 2012 9:17:40 PM
*/
public class TcpChannelTest
public String serverHost = "localhost";
public int serverPort = 12345;
private ServerSocketChannel server;
private int clientSerial = 0;
private int clientCount = 5;
// test tcp non-blocking channel,
@Test
public void testTcpNonBlockingChanne() throws IOException, InterruptedException
// start server
startServerNonBlocking();
Thread.sleep(500); // wait server to be ready, before start client,
// start clients
for (int i = 0; i < clientCount; i++)
startClientOnce();
// shutdown server,
Thread.sleep(500); // wait client to be handled,
shutdownServer();
// start non-blocking server,
private void startServerNonBlocking() throws IOException
new Thread(new Runnable()
@Override
public void run()
try
server = ServerSocketChannel.open();
server.socket().bind(new InetSocketAddress(serverHost, serverPort)); // bind,
server.configureBlocking(false); // non-blocking mode,
Selector selector = Selector.open();
server.register(selector, SelectionKey.OP_ACCEPT);
while (true)
selector.select();
Set<SelectionKey> readyKeys = selector.selectedKeys();
// process each ready key...
Iterator<SelectionKey> iterator = readyKeys.iterator();
while (iterator.hasNext())
SelectionKey key = (SelectionKey) iterator.next();
iterator.remove();
if (key.isAcceptable())
SocketChannel client = server.accept();
System.out.printf("[%s]:\t%s\n", Thread.currentThread().getName(), "accept connection");
client.configureBlocking(false);
// prepare for read,
client.register(selector, SelectionKey.OP_READ);
else if (key.isReadable())
// read
SocketChannel client = (SocketChannel) key.channel();
ByteBuffer inBuf = ByteBuffer.allocate(1024);
while (client.read(inBuf) > 0)
System.out.printf("[%s]:\t%s\n", Thread.currentThread().getName(), new String(inBuf.array(), StandardCharsets.UTF_8));
// prepare for write,
client.register(selector, SelectionKey.OP_WRITE);
else if (key.isWritable())
SocketChannel client = (SocketChannel) key.channel();
String response = "hi - from non-blocking server";
byte[] bs = response.getBytes(StandardCharsets.UTF_8);
ByteBuffer buffer = ByteBuffer.wrap(bs);
client.write(buffer);
// switch to read, and disable write,
client.register(selector, SelectionKey.OP_READ);
catch (IOException e)
e.printStackTrace();
, "t-server-threads").start();
// close server,
private void shutdownServer()
try
if (server != null)
server.close();
catch (IOException e)
e.printStackTrace();
/**
* <p>
* tcp client - via channel,
* </p>
* <p>
* It send once request.
* </p>
*
* @throws IOException
*/
private void startClientOnce() throws IOException
// start client in a new thread
new Thread(new Runnable()
@Override
public void run()
try
SocketChannel client = SocketChannel.open(new InetSocketAddress(serverHost, serverPort));
// write
String request = "hello - from client [" + Thread.currentThread().getName() + "";
byte[] bs = request.getBytes(StandardCharsets.UTF_8);
ByteBuffer buffer = ByteBuffer.wrap(bs);
while (buffer.hasRemaining())
client.write(buffer);
// read
ByteBuffer inBuf = ByteBuffer.allocate(1024);
while (client.read(inBuf) > 0)
System.out.printf("[%s]:\t%s\n", Thread.currentThread().getName(), new String(inBuf.array(), StandardCharsets.UTF_8));
client.close();
catch (IOException e)
e.printStackTrace();
, "t-channelClient-" + clientSerial++).start();
【讨论】：
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