chargen.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.examples.unix;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.InterruptedIOException;
import java.net.InetAddress;
import java.net.SocketException;
import java.nio.charset.Charset;
import java.time.Duration;

import org.apache.commons.net.chargen.CharGenTCPClient;
import org.apache.commons.net.chargen.CharGenUDPClient;

/**
 * This is an example program demonstrating how to use the CharGenTCPClient and CharGenUDPClient classes. This program connects to the default chargen service
 * port of a specified server, then reads 100 lines from of generated output, writing each line to standard output, and then closes the connection. The UDP
 * invocation of the program sends 50 datagrams, printing the reply to each. The default is to use the TCP port. Use the -udp flag to use the UDP port.
 * <p>
 * Usage: chargen [-udp] <hostname>
 */
public final class chargen {

    public static void chargenTCP(final String host) throws IOException {
        int lines = 100;
        String line;
        final CharGenTCPClient client = new CharGenTCPClient();

        // We want to timeout if a response takes longer than 60 seconds
        client.setDefaultTimeout(60000);
        client.connect(host);
        try (final BufferedReader chargenInput = new BufferedReader(new InputStreamReader(client.getInputStream(), Charset.defaultCharset()))) {

            // We assume the chargen service outputs lines, but it really doesn't
            // have to, so this code might actually not work if no newlines are
            // present.
            while (lines-- > 0) {
                if ((line = chargenInput.readLine()) == null) {
                    break;
                }
                System.out.println(line);
            }
        }
        client.disconnect();
    }

    public static void chargenUDP(final String host) throws IOException {
        int packets = 50;
        byte[] data;
        final InetAddress address;

        address = InetAddress.getByName(host);
        try (CharGenUDPClient client = new CharGenUDPClient()) {

            client.open();
            // If we don't receive a return packet within 5 seconds, assume
            // the packet is lost.
            client.setSoTimeout(Duration.ofSeconds(5));

            while (packets-- > 0) {
                client.send(address);

                try {
                    data = client.receive();
                }
                // Here we catch both SocketException and InterruptedIOException,
                // because even though the JDK 1.1 docs claim that
                // InterruptedIOException is thrown on a timeout, it seems
                // SocketException is also thrown.
                catch (final SocketException e) {
                    // We timed out and assume the packet is lost.
                    System.err.println("SocketException: Timed out and dropped packet");
                    continue;
                } catch (final InterruptedIOException e) {
                    // We timed out and assume the packet is lost.
                    System.err.println("InterruptedIOException: Timed out and dropped packet");
                    continue;
                }
                System.out.write(data);
                System.out.flush();
            }

        }
    }

    public static void main(final String[] args) {

        if (args.length == 1) {
            try {
                chargenTCP(args[0]);
            } catch (final IOException e) {
                e.printStackTrace();
                System.exit(1);
            }
        } else if (args.length == 2 && args[0].equals("-udp")) {
            try {
                chargenUDP(args[1]);
            } catch (final IOException e) {
                e.printStackTrace();
                System.exit(1);
            }
        } else {
            System.err.println("Usage: chargen [-udp] <hostname>");
            System.exit(1);
        }

    }

}