我想使用NIO向/从远程机器发送/接收数据。我可以随时发送或接收数据，当我需要发送数据时我只是发送它而不需要远程机器的任何查询，而远程机器定期向我发送数据。我不了解NIO机制。什么在Selector SelectionKey上生成，读取或写入事件？是否可以在我这边只使用一个ServerSocketChannel，从远程机器读取数据并向其写入数据？这就是我的理解，但我不知道如何触发写作事件......谢谢你的解释。
我已经做了一些编码，我可以读取来自远程机器的数据，但无法写入。我使用Selector，我不知道如何写数据。记录的消息“句柄写入”永远不会被写入，但在wireshark中，我可以看到我的数据包。
public class ServerSelector {
private static final Logger logger = Logger.getLogger(ServerSelector.class.getName());
private static final int TIMEOUT = 3000; // Wait timeout (milliseconds)
private static final int MAXTRIES = 3;
private final Selector selector;
public ServerSelector(Controller controller, int... servPorts) throws IOException {
if (servPorts.length <= 0) {
throw new IllegalArgumentException("Parameter(s) : <Port>...");
}
Handler consolehHandler = new ConsoleHandler();
consolehHandler.setLevel(Level.INFO);
logger.addHandler(consolehHandler);
// Create a selector to multiplex listening sockets and connections
selector = Selector.open();
// Create listening socket channel for each port and register selector
for (int servPort : servPorts) {
ServerSocketChannel listnChannel = ServerSocketChannel.open();
listnChannel.socket().bind(new InetSocketAddress(servPort));
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
IOProtocol protocol = new IOProtocol();
int tries = 0;
// Run forever, processing available I/O operations
while (tries < MAXTRIES) {
// Wait for some channel to be ready (or timeout)
if (selector.select(TIMEOUT) == 0) { // returns # of ready chans
System.out.println(".");
tries += 1;
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 a bit mask
// Server socket channel has pending connection requests?
if (key.isAcceptable()) {
logger.log(Level.INFO, "handle accept");
protocol.handleAccept(key, controller);
}
// Client socket channel has pending data?
if (key.isReadable()) {
logger.log(Level.INFO, "handle 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()) {
logger.log(Level.INFO, "handle write");
protocol.handleWrite(key);
}
keyIter.remove(); // remove from set of selected keys
tries = 0;
}
}
}
}
协议
public class IOProtocol implements Protocol {
private static final Logger logger = Logger.getLogger(IOProtocol.class.getName());
IOProtocol() {
Handler consolehHandler = new ConsoleHandler();
consolehHandler.setLevel(Level.INFO);
logger.addHandler(consolehHandler);
}
/**
*
* @param key
* @throws IOException
*/
@Override
public void handleAccept(SelectionKey key, Controller controller) throws IOException {
SocketChannel clntChan = ((ServerSocketChannel) key.channel()).accept();
clntChan.configureBlocking(false); // Must be nonblocking to register
controller.setCommChannel(clntChan);
// Register the selector with new channel for read and attach byte buffer
SelectionKey socketKey = clntChan.register(key.selector(), SelectionKey.OP_READ | SelectionKey.OP_WRITE, controller);
}
/**
* Client socket channel has pending data
*
* @param key
* @throws IOException
*/
@Override
public void handleRead(SelectionKey key) throws IOException {
Controller ctrller = (Controller)key.attachment();
try {
ctrller.readData();
} catch (CommandUnknownException ex) {
logger.log(Level.SEVERE, null, ex);
}
key.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);
}
/**
* Channel is available for writing, and key is valid (i.e., client channel
* not closed).
*
* @param key
* @throws IOException
*/
@Override
public void handleWrite(SelectionKey key) throws IOException {
Controller ctrl = (Controller)key.attachment();
ctrl.writePendingData();
if (!buf.hasRemaining()) { // Buffer completely written ?
// Nothing left, so no longer interested in writes
key.interestOps(SelectionKey.OP_READ);
}
buf.compact();
}
}
控制器
/**
* Fill buffer with data.
* @param msg The data to be sent
* @throws IOException
*/
private void writeData(AbstractMsg msg) throws IOException {
//
writeBuffer = ByteBuffer.allocate(msg.getSize() + 4);
writeBuffer.putInt(msg.getSize());
msg.writeHeader(writeBuffer);
msg.writeData(writeBuffer);
logger.log(Level.INFO, "Write data - message size : {0}", new Object[]{msg.getSize()});
logger.log(Level.INFO, "Write data - message : {0}", new Object[]{msg});
}
/**
* Write to the SocketChannel
* @throws IOException
*/
public void writePendingData() throws IOException {
commChannel.write(writeBuffer);
}
答案 0 :(得分：1)
ServerSocketChannel用于建立连接，但不发送数据。每个连接需要一个ServerSocketChannel和一个SocketChannel。
使用SocketChannel进行阅读和写作的示例：
ByteBuffer buf = ByteBuffer.allocate(48);
int bytesRead = socketChannel.read(buf);
您的程序将在第二行睡眠，直到数据到来。您需要将此代码置于无限循环中并在后台Thread中运行它。当数据出现时，你可以从这个线程处理它，然后等待另一个数据来。
ByteBuffer buf = ByteBuffer.allocate(48);
buf.clear();
buf.put("Hello!".getBytes());
buf.flip();
while(buf.hasRemaining()) {
channel.write(buf);
}
没有阻止方法，因此如果你发送小字节缓冲区，你可以从主Thread调用它。
添加：
不要在新连接上设置OP_WRITE键。只有1个}}。当您想要写一些数据时，您需要通知选择器您要发送内容并在事件循环中发送它。好的解决方案是发出OP_READ个消息。然后按照以下步骤操作：
Queue Queue设置为频道的密钥OP_WRITE循环中，您将拥有while (keyIter.hasNext())，从队列中写入所有数据并移除writable key密钥。我很难理解你的代码，但我想你会发现问题是什么。此外，如果您只想拥有一个连接，则无需使用OP_WRITE。你绑定一些Selector时很奇怪。
答案 1 :(得分：0)
我建议你使用阻塞NIO（这是SocketChannel的默认行为）你不需要使用Selector但是你可以使用一个线程进行读取而另一个线程用于写入。
根据你的例子。
private final ByteBuffer writeBuffer = ByteBuffer.allocateDirect(1024*1024);
private void writeData(AbstractMsg msg) {
writeBuffer.clear();
writeBuffer.putInt(0); // set later
msg.writeHeader(writeBuffer);
msg.writeData(writeBuffer);
writeBuffer.putInt(0, writeBuffer.position());
writeBuffer.flip();
while(writeBuffer.hasRemaining())
commChannel.write(writeBuffer);
}
答案 2 :(得分：0)
Selector SelectionKey上生成，读取或写入事件的内容是什么？
OP_READ：套接字接收缓冲区中存在数据或EOS。
OP_WRITE：套接字发送缓冲区中的空间。