84 lines
2.1 KiB
Java
84 lines
2.1 KiB
Java
TimeQuery
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import java.io.*;
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import java.net.*;
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import java.nio.*;
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import java.nio.channels.*;
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import java.nio.charset.*;
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import java.util.regex.*;
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public class TimeQuery {
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// The standard daytime port
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private static int DAYTIME_PORT = 13;
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// The port we'll actually use
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private static int port = DAYTIME_PORT;
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// Charset and decoder for US-ASCII
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private static Charset charset = Charset.forName("US-ASCII");
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private static CharsetDecoder decoder = charset.newDecoder();
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// Direct byte buffer for reading
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private static ByteBuffer dbuf = ByteBuffer.allocateDirect(1024);
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// Ask the given host what time it is
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//
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private static void query(String host) throws IOException {
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InetSocketAddress isa
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= new InetSocketAddress(InetAddress.getByName(host), port);
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SocketChannel sc = null;
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try {
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// Connect
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sc = SocketChannel.open();
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sc.connect(isa);
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// Read the time from the remote host. For simplicity we assume
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// that the time comes back to us in a single packet, so that we
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// only need to read once.
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dbuf.clear();
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sc.read(dbuf);
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// Print the remote address and the received time
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dbuf.flip();
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CharBuffer cb = decoder.decode(dbuf);
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System.out.print(isa + " : " + cb);
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} finally {
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// Make sure we close the channel (and hence the socket)
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if (sc != null)
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sc.close();
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}
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}
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public static void main(String[] args) {
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if (args.length < 1) {
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System.err.println("Usage: java TimeQuery [port] host...");
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return;
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}
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int firstArg = 0;
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// If the first argument is a string of digits then we take that
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// to be the port number
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if (Pattern.matches("[0-9]+", args[0])) {
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port = Integer.parseInt(args[0]);
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firstArg = 1;
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}
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for (int i = firstArg; i < args.length; i++) {
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String host = args[i];
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try {
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query(host);
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} catch (IOException x) {
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System.err.println(host + ": " + x);
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}
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}
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}
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}
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