我是NIO和NIO2的新手。我一直在玩一个Echo服务器示例代码，它可以完美运行。我开始写一个类似的客户端。我的目标是让多个客户端套接字连接在一个主线程上运行。
我确实得到了OP_CONNECT，然后选择器没有返回并超时： while（Selector.select（10000）＆gt; 0）{ .... }
如果我忽略选择器并开始用socketChannel.read（...）读取数据，我可以读取数据。因此，数据已准备好被读取，但我只是没有让Selector.select（10000）返回一些键。
以下是完整的源代码，我真的很感激任何帮助：
package com.maker.webscraping.nio;
import java.io.IOException;
import java.net.StandardSocketOptions;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.Iterator;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.ConcurrentHashMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class EchoClient2 {
private static final Logger logger = LoggerFactory.getLogger(EchoClient2.class);
private static final Map<SocketChannel, EchoClient2> mapClients = new ConcurrentHashMap<>();
private static final int DEFAULT_PORT = 5555;
private static final String IP = "127.0.0.1";
private final int clientID;
private final ByteBuffer buffer;
private final SocketChannel socketChannel;
private final CharsetDecoder decoder;
public int getClientID() {
return clientID;
}
public ByteBuffer getBuffer() {
return buffer;
}
public CharsetDecoder getDecoder() {
return decoder;
}
//private static Selector selector = null;
public static void main(String[] args) {
Selector selector = null;
try {
selector = Selector.open();
if (!selector.isOpen())
throw new RuntimeException("Selector closed!");
EchoClient2[] clients = new EchoClient2[2];
clients[0] = new EchoClient2(0, selector);
// wait for incomming events
while (selector.select(10000)>0) {
Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
while (keys.hasNext()) {
SelectionKey key = (SelectionKey) keys.next();
try (SocketChannel socketChannel = (SocketChannel) key.channel()) {
if (key.isConnectable()) {
// connected
logger.info("Client:{} connected!", clients[0].getClientID());
key.interestOps(SelectionKey.OP_READ); // <-- desprete tries
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE); // <-- desprete tries
logger.info("R:{}, W:{}, C:{}, validOps:{}", SelectionKey.OP_READ, SelectionKey.OP_WRITE, SelectionKey.OP_CONNECT, socketChannel.validOps());
// close pending connections
if (socketChannel.isConnectionPending()) {
socketChannel.finishConnect();
}
read(key,selector); // <-- desprete tries
if (key.isReadable()) {
read(key,selector);
}// else if (key.isWritable()) {
// this.writeOP(key);
//}
}
} catch (IOException e) {
logger.error("SocketChannel Exception!", e);
}
}
}
} catch (IOException e) {
logger.error("Selector IOException!", e);
} finally {
try {
selector.close();
} catch (IOException e) {}
}
}
public EchoClient2(int clientID, Selector selector) throws IOException {
this.clientID = clientID;
buffer = ByteBuffer.allocateDirect(2 * 1024);
Charset charset = Charset.defaultCharset();
decoder = charset.newDecoder();
// if (selector==null)
// selector = Selector.open();
socketChannel = SocketChannel.open();
if ((socketChannel.isOpen()) && (selector.isOpen())) {
// configure non-blocking mode
socketChannel.configureBlocking(false);
// set some options
socketChannel.setOption(StandardSocketOptions.SO_RCVBUF,
128 * 1024);
socketChannel.setOption(StandardSocketOptions.SO_SNDBUF,
128 * 1024);
socketChannel.setOption(StandardSocketOptions.SO_KEEPALIVE,
true);
socketChannel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ | SelectionKey.OP_WRITE);
//socketChannel.register(selector, SelectionKey.OP_CONNECT);
// connect to remote host
socketChannel.connect(new java.net.InetSocketAddress(IP, DEFAULT_PORT));
// add it to the map
mapClients.put(socketChannel, this);
} else
throw new RuntimeException("Channel or Selector closed!");
}
// isReadable returned true
private static int read(SelectionKey key, Selector selector) {
try {
SocketChannel socketChannel = (SocketChannel) key.channel();
EchoClient2 client = mapClients.get(socketChannel);
ByteBuffer buffer = client.getBuffer();
buffer.clear();
int numRead = -1;
try {
numRead = socketChannel.read(buffer);
} catch (IOException e) {
System.err.println("Cannot read error!");
}
if (numRead == -1) {
mapClients.remove(socketChannel);
System.out.println("Connection closed by: " + socketChannel.getRemoteAddress());
socketChannel.close();
key.cancel();
return 1;
}
if (numRead == 0)
throw new RuntimeException("numRead is 0!!!");
buffer.flip();
CharBuffer charBuffer = client.getDecoder().decode(buffer);
System.out.println("server says:" + charBuffer.toString());
if (buffer.hasRemaining()) {
buffer.compact();
} else {
buffer.clear();
}
int r = new Random().nextInt(100);
//if (r == 50) {
// System.out.println("50 was generated! Close the socket channel!");
// return 1;
//}
ByteBuffer randomBuffer = ByteBuffer.wrap("Random number:".concat(String.valueOf(r))
.getBytes("UTF-8"));
socketChannel.write(randomBuffer);
key.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE); // <-- desprete tries
} catch (IOException e) {
logger.error("IOException inside read!", e);
}
return 0;
}
}
谢谢，
答案 0 :(得分：0)
while (selector.select(10000)>0)
此代码已经错误。它将在第一次发生选择超时时停止选择。它应该是：
while (selector.isOpen())
{
if (selector.select(10000) > 0)
{
// ...
}
}
还有其他问题。
finishConnect()返回true. key.isReadable()为真时阅读。你需要一个单独的测试，而不是一个捎带到isConnectable()案例。isWritable(). OP_WRITE，或者在你尝试写东西时获得零长度回报后更好。 OP_WRITE表示套接字发送缓冲区未满。几乎总是如此。keys.remove()之后致电keys.next(),，否则您将一遍又一遍地获得相同的选定密钥。选择器不会清除所选键集。// close pending connections完全不正确。isConnectionPending()电话是多余的。当然它正在等待，这就是你得到OP_CONNECT.