Java TCP/IP Socket编程·源代码

import java.io.IOException; import java.net.InetSocketAddress; import java.net.SocketAddress; import java.nio.ByteBuffer; import java.nio.channels.DatagramChannel; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.util.Iterator; public class UDPEchoServerSelector { private static final int TIMEOUT = 3000; // Wait timeout (milliseconds) private static final int ECHOMAX = 255; // Maximum size of echo datagram public static void main(String[] args) throws IOException { if (args.length != 1) // Test for correct argument list throw new IllegalArgumentException("Parameter(s): <Port>"); int servPort = Integer.parseInt(args[0]); // Create a selector to multiplex client connections. Selector selector = Selector.open(); DatagramChannel channel = DatagramChannel.open(); channel.configureBlocking(false); channel.socket().bind(new InetSocketAddress(servPort)); channel.register(selector, SelectionKey.OP_READ, new ClientRecord()); while (true) { // Run forever, receiving and echoing datagrams // Wait for task or until timeout expires if (selector.select(TIMEOUT) == 0) { 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 // Client socket channel has pending data? if (key.isReadable()) handleRead(key); // Client socket channel is available for writing and // key is valid (i.e., channel not closed). if (key.isValid() && key.isWritable()) handleWrite(key); keyIter.remove(); } } } public static void handleRead(SelectionKey key) throws IOException { DatagramChannel channel = (DatagramChannel) key.channel(); ClientRecord clntRec = (ClientRecord) key.attachment(); clntRec.buffer.clear(); // Prepare buffer for receiving clntRec.clientAddress = channel.receive(clntRec.buffer); if (clntRec.clientAddress != null) { // Did we receive something? // Register write with the selector key.interestOps(SelectionKey.OP_WRITE); } } public static void handleWrite(SelectionKey key) throws IOException { DatagramChannel channel = (DatagramChannel) key.channel(); ClientRecord clntRec = (ClientRecord) key.attachment(); clntRec.buffer.flip(); // Prepare buffer for sending int bytesSent = channel.send(clntRec.buffer, clntRec.clientAddress); if (bytesSent != 0) { // Buffer completely written? // No longer interested in writes key.interestOps(SelectionKey.OP_READ); } } static class ClientRecord { public SocketAddress clientAddress; public ByteBuffer buffer = ByteBuffer.allocate(ECHOMAX); } }