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我想使用NIO向/從遠程機器發送/接收數據。我可以在任何時候發送或接收數據，當我需要發送數據時，只需發送數據而不需要遠程機器的任何查詢，而遠程機器則會定期向我發送數據。我不明白NIO機制。什麼在Selector SelectionKey上生成並讀取或寫入事件？是否可以在我身邊只使用一個ServerSocketChannel，從遠程機器讀取數據並將數據寫入它？這是我的理解，但我不知道如何觸發寫作事件......感謝您的解釋。Java遠程機器上的NIO讀寫
我已經做了一些編碼，我可以讀取從遠端機器進來的數據，但不能寫入。我使用選擇器，我不知道如何寫數據。記錄的消息「句柄寫入」從不寫入，但在wireshark中，我可以看到我的數據包。
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;
}
}
}
}
協議
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);
}
我貼了一些代碼 – jerome
編輯我的回答 – alaster
這些方法都是阻塞的，除非你把通道設置爲非阻塞模式。沒有必要「通知選擇器你想發送什麼」。傳出消息的隊列沒有必要。太不準確。 -1。 – EJP