jdk-24/test/jdk/java/net/Socket/UdpSocket.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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/**
 * @test
 * @run testng/othervm -Djava.security.manager=allow -Dsun.net.maxDatagramSockets=32 UdpSocket
 * @summary Basic test for a Socket to a UDP socket
 */

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.security.Permission;
import java.util.Arrays;
import java.util.ArrayDeque;
import java.util.Deque;
import java.net.BindException;

import org.testng.annotations.Test;
import static org.testng.Assert.*;

@Test
public class UdpSocket {

    /**
     * Test using the Socket API to send/receive datagrams
     */
    public void testSendReceive() throws IOException {
        final String MESSAGE = "hello";

        try (DatagramChannel dc = DatagramChannel.open()) {
            var loopback = InetAddress.getLoopbackAddress();
            dc.bind(new InetSocketAddress(loopback, 0));

            int port = ((InetSocketAddress) dc.getLocalAddress()).getPort();
            try (Socket s = new Socket(loopback, port, false)) {
                // send datagram with socket output stream
                byte[] array1 = MESSAGE.getBytes("UTF-8");
                s.getOutputStream().write(array1);

                // receive the datagram
                var buf = ByteBuffer.allocate(100);
                SocketAddress remote = dc.receive(buf);
                buf.flip();
                assertTrue(buf.remaining() == MESSAGE.length(), "Unexpected size");

                // echo the datagram
                dc.send(buf, remote);

                // receive datagram with the socket input stream
                byte[] array2 = new byte[100];
                int n = s.getInputStream().read(array2);
                assertTrue(n == MESSAGE.length(), "Unexpected size");
                assertEquals(Arrays.copyOf(array1, n), Arrays.copyOf(array2, n),
                            "Unexpected contents");
            }
        }
    }

    /**
     * Test that the number of UDP sockets is limited when running with a
     * security manager.
     */
    public void testMaxSockets() throws Exception {
        int limit = Integer.getInteger("sun.net.maxDatagramSockets");

        // security manager grants all permissions
        var securityManager = new SecurityManager() {
            @Override public void checkPermission(Permission perm) { }
        };

        System.setSecurityManager(securityManager);
        Deque<Socket> sockets = new ArrayDeque<>();
        try {
            // create the maximum number of sockets
            for (int i=0; i<limit; i++) {
                sockets.offer(newUdpSocket());
            }

            // try to create another socket - should fail
            try {
                Socket s = newUdpSocket();
                s.close();
                assertTrue(false);
            } catch (IOException expected) { }

            // close one socket
            sockets.pop().close();

            // try to create another socket - should succeed
            Socket s = newUdpSocket();

            // unreference the socket and wait for it to be closed by the cleaner
            var ref = new WeakReference<>(s);
            s = null;
            while (ref.get() != null) {
                System.gc();
                Thread.sleep(100);
            }

            // try to create another socket - should succeed
            s = newUdpSocket();
            s.close();
        } finally {
            closeAll(sockets);
            System.setSecurityManager(null);
        }
    }


    private Socket newUdpSocket() throws IOException {
        Socket s = null;

        try {
            s = new Socket(InetAddress.getLoopbackAddress(), 8000, false);
        } catch (BindException unexpected) {
            System.out.println("BindException caught retry Socket creation");
            s = new Socket(InetAddress.getLoopbackAddress(), 8000, false);
        }
        return s;
    }

    private void closeAll(Deque<Socket> sockets) throws IOException {
        Socket s;
        while ((s = sockets.poll()) != null) {
            s.close();
        }
    }
}