https://openjdk.java.net/ 
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 * Copyright (c) 1995, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package java.net;

import java.io.IOException;
import java.nio.channels.DatagramChannel;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import java.util.Set;
import java.util.Collections;


This class represents a socket for sending and receiving datagram packets.

A datagram socket is the sending or receiving point for a packet
delivery service. Each packet sent or received on a datagram socket
is individually addressed and routed. Multiple packets sent from
one machine to another may be routed differently, and may arrive in
any order.

 Where possible, a newly constructed DatagramSocket has the SO_BROADCAST socket option enabled so as to allow the transmission of broadcast datagrams. In order to receive broadcast packets a DatagramSocket should be bound to the wildcard address. In some implementations, broadcast packets may also be received when a DatagramSocket is bound to a more specific address. 
 Example: 
             DatagramSocket s = new DatagramSocket(null);
             s.bind(new InetSocketAddress(8888));
 Which is equivalent to: 
             DatagramSocket s = new DatagramSocket(8888);
 Both cases will create a DatagramSocket able to receive broadcasts on UDP port 8888. 
Author: Pavani Diwanji
See Also:
Since:1.0
/**
 * This class represents a socket for sending and receiving datagram packets.
 *
 * <p>A datagram socket is the sending or receiving point for a packet
 * delivery service. Each packet sent or received on a datagram socket
 * is individually addressed and routed. Multiple packets sent from
 * one machine to another may be routed differently, and may arrive in
 * any order.
 *
 * <p> Where possible, a newly constructed {@code DatagramSocket} has the
 * {@link SocketOptions#SO_BROADCAST SO_BROADCAST} socket option enabled so as
 * to allow the transmission of broadcast datagrams. In order to receive
 * broadcast packets a DatagramSocket should be bound to the wildcard address.
 * In some implementations, broadcast packets may also be received when
 * a DatagramSocket is bound to a more specific address.
 * <p>
 * Example:
 * {@code
 *              DatagramSocket s = new DatagramSocket(null);
 *              s.bind(new InetSocketAddress(8888));
 * }
 * Which is equivalent to:
 * {@code
 *              DatagramSocket s = new DatagramSocket(8888);
 * }
 * Both cases will create a DatagramSocket able to receive broadcasts on
 * UDP port 8888.
 *
 * @author  Pavani Diwanji
 * @see     java.net.DatagramPacket
 * @see     java.nio.channels.DatagramChannel
 * @since 1.0
 */
public
class DatagramSocket implements java.io.Closeable {
    
Various states of this socket.

/**
     * Various states of this socket.
     */
    private boolean created = false;
    private boolean bound = false;
    private boolean closed = false;
    private Object closeLock = new Object();

    /*
     * The implementation of this DatagramSocket.
     */
    DatagramSocketImpl impl;

    
Are we using an older DatagramSocketImpl?

/**
     * Are we using an older DatagramSocketImpl?
     */
    boolean oldImpl = false;

    
Set when a socket is ST_CONNECTED until we are certain
that any packets which might have been received prior
to calling connect() but not read by the application
have been read. During this time we check the source
address of all packets received to be sure they are from
the connected destination. Other packets are read but
silently dropped.

/**
     * Set when a socket is ST_CONNECTED until we are certain
     * that any packets which might have been received prior
     * to calling connect() but not read by the application
     * have been read. During this time we check the source
     * address of all packets received to be sure they are from
     * the connected destination. Other packets are read but
     * silently dropped.
     */
    private boolean explicitFilter = false;
    private int bytesLeftToFilter;
    /*
     * Connection state:
     * ST_NOT_CONNECTED = socket not connected
     * ST_CONNECTED = socket connected
     * ST_CONNECTED_NO_IMPL = socket connected but not at impl level
     */
    static final int ST_NOT_CONNECTED = 0;
    static final int ST_CONNECTED = 1;
    static final int ST_CONNECTED_NO_IMPL = 2;

    int connectState = ST_NOT_CONNECTED;

    /*
     * Connected address & port
     */
    InetAddress connectedAddress = null;
    int connectedPort = -1;

    
Connects this socket to a remote socket address (IP address + port number).
Binds socket if not already bound.

Params:
  • address – The remote address.
  • port –    The remote port
Throws:
/**
     * Connects this socket to a remote socket address (IP address + port number).
     * Binds socket if not already bound.
     *
     * @param   address The remote address.
     * @param   port    The remote port
     * @throws  SocketException if binding the socket fails.
     */
    private synchronized void connectInternal(InetAddress address, int port) throws SocketException {
        if (port < 0 || port > 0xFFFF) {
            throw new IllegalArgumentException("connect: " + port);
        }
        if (address == null) {
            throw new IllegalArgumentException("connect: null address");
        }
        checkAddress (address, "connect");
        if (isClosed())
            return;
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            if (address.isMulticastAddress()) {
                security.checkMulticast(address);
            } else {
                security.checkConnect(address.getHostAddress(), port);
                security.checkAccept(address.getHostAddress(), port);
            }
        }

        if (!isBound())
          bind(new InetSocketAddress(0));

        // old impls do not support connect/disconnect
        if (oldImpl || (impl instanceof AbstractPlainDatagramSocketImpl &&
             ((AbstractPlainDatagramSocketImpl)impl).nativeConnectDisabled())) {
            connectState = ST_CONNECTED_NO_IMPL;
        } else {
            try {
                getImpl().connect(address, port);

                // socket is now connected by the impl
                connectState = ST_CONNECTED;
                // Do we need to filter some packets?
                int avail = getImpl().dataAvailable();
                if (avail == -1) {
                    throw new SocketException();
                }
                explicitFilter = avail > 0;
                if (explicitFilter) {
                    bytesLeftToFilter = getReceiveBufferSize();
                }
            } catch (SocketException se) {

                // connection will be emulated by DatagramSocket
                connectState = ST_CONNECTED_NO_IMPL;
            }
        }

        connectedAddress = address;
        connectedPort = port;
    }


    
Constructs a datagram socket and binds it to any available port on the local host machine. The socket will be bound to the wildcard address, an IP address chosen by the kernel. 
If there is a security manager, its checkListen method is first called with 0 as its argument to ensure the operation is allowed. This could result in a SecurityException. 
Throws:
  • SocketException –  if the socket could not be opened,
              or the socket could not bind to the specified local port.
  • SecurityException –  if a security manager exists and its checkListen method doesn't allow the operation.
See Also:
/**
     * Constructs a datagram socket and binds it to any available port
     * on the local host machine.  The socket will be bound to the
     * {@link InetAddress#isAnyLocalAddress wildcard} address,
     * an IP address chosen by the kernel.
     *
     * <p>If there is a security manager,
     * its {@code checkListen} method is first called
     * with 0 as its argument to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @exception  SocketException  if the socket could not be opened,
     *               or the socket could not bind to the specified local port.
     * @exception  SecurityException  if a security manager exists and its
     *             {@code checkListen} method doesn't allow the operation.
     *
     * @see SecurityManager#checkListen
     */
    public DatagramSocket() throws SocketException {
        this(new InetSocketAddress(0));
    }

    
Creates an unbound datagram socket with the specified
DatagramSocketImpl.

Params:
  • impl – an instance of a DatagramSocketImpl
       the subclass wishes to use on the DatagramSocket.
Since:  1.4
/**
     * Creates an unbound datagram socket with the specified
     * DatagramSocketImpl.
     *
     * @param impl an instance of a <B>DatagramSocketImpl</B>
     *        the subclass wishes to use on the DatagramSocket.
     * @since   1.4
     */
    protected DatagramSocket(DatagramSocketImpl impl) {
        if (impl == null)
            throw new NullPointerException();
        this.impl = impl;
        checkOldImpl();
    }

    
Creates a datagram socket, bound to the specified local
socket address.

 If, if the address is null, creates an unbound socket. 
If there is a security manager, its checkListen method is first called with the port from the socket address as its argument to ensure the operation is allowed. This could result in a SecurityException. 
Params:
  • bindaddr – local socket address to bind, or null for an unbound socket.
Throws:
  • SocketException –  if the socket could not be opened,
              or the socket could not bind to the specified local port.
  • SecurityException –  if a security manager exists and its checkListen method doesn't allow the operation.
See Also:
Since:  1.4
/**
     * Creates a datagram socket, bound to the specified local
     * socket address.
     * <p>
     * If, if the address is {@code null}, creates an unbound socket.
     *
     * <p>If there is a security manager,
     * its {@code checkListen} method is first called
     * with the port from the socket address
     * as its argument to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param bindaddr local socket address to bind, or {@code null}
     *                 for an unbound socket.
     *
     * @exception  SocketException  if the socket could not be opened,
     *               or the socket could not bind to the specified local port.
     * @exception  SecurityException  if a security manager exists and its
     *             {@code checkListen} method doesn't allow the operation.
     *
     * @see SecurityManager#checkListen
     * @since   1.4
     */
    public DatagramSocket(SocketAddress bindaddr) throws SocketException {
        // create a datagram socket.
        createImpl();
        if (bindaddr != null) {
            try {
                bind(bindaddr);
            } finally {
                if (!isBound())
                    close();
            }
        }
    }

    
Constructs a datagram socket and binds it to the specified port on the local host machine. The socket will be bound to the wildcard address, an IP address chosen by the kernel. 
If there is a security manager, its checkListen method is first called with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException. 
Params:
  • port – port to use.
Throws:
  • SocketException –  if the socket could not be opened,
              or the socket could not bind to the specified local port.
  • SecurityException –  if a security manager exists and its checkListen method doesn't allow the operation.
See Also:
/**
     * Constructs a datagram socket and binds it to the specified port
     * on the local host machine.  The socket will be bound to the
     * {@link InetAddress#isAnyLocalAddress wildcard} address,
     * an IP address chosen by the kernel.
     *
     * <p>If there is a security manager,
     * its {@code checkListen} method is first called
     * with the {@code port} argument
     * as its argument to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param      port port to use.
     * @exception  SocketException  if the socket could not be opened,
     *               or the socket could not bind to the specified local port.
     * @exception  SecurityException  if a security manager exists and its
     *             {@code checkListen} method doesn't allow the operation.
     *
     * @see SecurityManager#checkListen
     */
    public DatagramSocket(int port) throws SocketException {
        this(port, null);
    }

    
Creates a datagram socket, bound to the specified local address. The local port must be between 0 and 65535 inclusive. If the IP address is 0.0.0.0, the socket will be bound to the wildcard address, an IP address chosen by the kernel. 
If there is a security manager, its checkListen method is first called with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException. 
Params:
  • port – local port to use
  • laddr – local address to bind
Throws:
  • SocketException –  if the socket could not be opened,
              or the socket could not bind to the specified local port.
  • SecurityException –  if a security manager exists and its checkListen method doesn't allow the operation.
See Also:
Since:  1.1
/**
     * Creates a datagram socket, bound to the specified local
     * address.  The local port must be between 0 and 65535 inclusive.
     * If the IP address is 0.0.0.0, the socket will be bound to the
     * {@link InetAddress#isAnyLocalAddress wildcard} address,
     * an IP address chosen by the kernel.
     *
     * <p>If there is a security manager,
     * its {@code checkListen} method is first called
     * with the {@code port} argument
     * as its argument to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param port local port to use
     * @param laddr local address to bind
     *
     * @exception  SocketException  if the socket could not be opened,
     *               or the socket could not bind to the specified local port.
     * @exception  SecurityException  if a security manager exists and its
     *             {@code checkListen} method doesn't allow the operation.
     *
     * @see SecurityManager#checkListen
     * @since   1.1
     */
    public DatagramSocket(int port, InetAddress laddr) throws SocketException {
        this(new InetSocketAddress(laddr, port));
    }

    private void checkOldImpl() {
        if (impl == null)
            return;
        // DatagramSocketImpl.peekdata() is a protected method, therefore we need to use
        // getDeclaredMethod, therefore we need permission to access the member
        try {
            AccessController.doPrivileged(
                new PrivilegedExceptionAction<>() {
                    public Void run() throws NoSuchMethodException {
                        Class<?>[] cl = new Class<?>[1];
                        cl[0] = DatagramPacket.class;
                        impl.getClass().getDeclaredMethod("peekData", cl);
                        return null;
                    }
                });
        } catch (java.security.PrivilegedActionException e) {
            oldImpl = true;
        }
    }

    static Class<?> implClass = null;

    void createImpl() throws SocketException {
        if (impl == null) {
            if (factory != null) {
                impl = factory.createDatagramSocketImpl();
                checkOldImpl();
            } else {
                boolean isMulticast = (this instanceof MulticastSocket) ? true : false;
                impl = DefaultDatagramSocketImplFactory.createDatagramSocketImpl(isMulticast);

                checkOldImpl();
            }
        }
        // creates a udp socket
        impl.create();
        impl.setDatagramSocket(this);
        created = true;
    }

    
Get the DatagramSocketImpl attached to this socket, creating it if necessary. 
Throws:
Returns: the DatagramSocketImpl attached to that DatagramSocket
Since:1.4
/**
     * Get the {@code DatagramSocketImpl} attached to this socket,
     * creating it if necessary.
     *
     * @return  the {@code DatagramSocketImpl} attached to that
     *          DatagramSocket
     * @throws SocketException if creation fails.
     * @since 1.4
     */
    DatagramSocketImpl getImpl() throws SocketException {
        if (!created)
            createImpl();
        return impl;
    }

    
Binds this DatagramSocket to a specific address and port.

 If the address is null, then the system will pick up an ephemeral port and a valid local address to bind the socket. 
Params:
  • addr – The address and port to bind to.
Throws:
  • SocketException – if any error happens during the bind, or if the
         socket is already bound.
  • SecurityException –  if a security manager exists and its checkListen method doesn't allow the operation.
  • IllegalArgumentException – if addr is a SocketAddress subclass
        not supported by this socket.
Since:1.4
/**
     * Binds this DatagramSocket to a specific address and port.
     * <p>
     * If the address is {@code null}, then the system will pick up
     * an ephemeral port and a valid local address to bind the socket.
     *
     * @param   addr The address and port to bind to.
     * @throws  SocketException if any error happens during the bind, or if the
     *          socket is already bound.
     * @throws  SecurityException  if a security manager exists and its
     *             {@code checkListen} method doesn't allow the operation.
     * @throws IllegalArgumentException if addr is a SocketAddress subclass
     *         not supported by this socket.
     * @since 1.4
     */
    public synchronized void bind(SocketAddress addr) throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        if (isBound())
            throw new SocketException("already bound");
        if (addr == null)
            addr = new InetSocketAddress(0);
        if (!(addr instanceof InetSocketAddress))
            throw new IllegalArgumentException("Unsupported address type!");
        InetSocketAddress epoint = (InetSocketAddress) addr;
        if (epoint.isUnresolved())
            throw new SocketException("Unresolved address");
        InetAddress iaddr = epoint.getAddress();
        int port = epoint.getPort();
        checkAddress(iaddr, "bind");
        SecurityManager sec = System.getSecurityManager();
        if (sec != null) {
            sec.checkListen(port);
        }
        try {
            getImpl().bind(port, iaddr);
        } catch (SocketException e) {
            getImpl().close();
            throw e;
        }
        bound = true;
    }

    void checkAddress (InetAddress addr, String op) {
        if (addr == null) {
            return;
        }
        if (!(addr instanceof Inet4Address || addr instanceof Inet6Address)) {
            throw new IllegalArgumentException(op + ": invalid address type");
        }
    }

    
Connects the socket to a remote address for this socket. When a
socket is connected to a remote address, packets may only be
sent to or received from that address. By default a datagram
socket is not connected.

If the remote destination to which the socket is connected does not
exist, or is otherwise unreachable, and if an ICMP destination unreachable
packet has been received for that address, then a subsequent call to
send or receive may throw a PortUnreachableException. Note, there is no
guarantee that the exception will be thrown.

 If a security manager has been installed then it is invoked to check access to the remote address. Specifically, if the given address is a multicast address, the security manager's 
checkMulticast method is invoked with the given address. Otherwise, the security manager's checkConnect and checkAccept methods are invoked, with the given address and port, to verify that datagrams are permitted to be sent and received respectively. 
 When a socket is connected, receive and send will not perform any security checks on incoming and outgoing packets, other than matching the packet's and the socket's address and port. On a send operation, if the packet's address is set and the packet's address and the socket's address do not match, an IllegalArgumentException will be thrown. A socket connected to a multicast address may only be used to send packets. 
Params:
  • address – the remote address for the socket
  • port – the remote port for the socket.
Throws:
See Also:
/**
     * Connects the socket to a remote address for this socket. When a
     * socket is connected to a remote address, packets may only be
     * sent to or received from that address. By default a datagram
     * socket is not connected.
     *
     * <p>If the remote destination to which the socket is connected does not
     * exist, or is otherwise unreachable, and if an ICMP destination unreachable
     * packet has been received for that address, then a subsequent call to
     * send or receive may throw a PortUnreachableException. Note, there is no
     * guarantee that the exception will be thrown.
     *
     * <p> If a security manager has been installed then it is invoked to check
     * access to the remote address. Specifically, if the given {@code address}
     * is a {@link InetAddress#isMulticastAddress multicast address},
     * the security manager's {@link
     * java.lang.SecurityManager#checkMulticast(InetAddress)
     * checkMulticast} method is invoked with the given {@code address}.
     * Otherwise, the security manager's {@link
     * java.lang.SecurityManager#checkConnect(String,int) checkConnect}
     * and {@link java.lang.SecurityManager#checkAccept checkAccept} methods
     * are invoked, with the given {@code address} and {@code port}, to
     * verify that datagrams are permitted to be sent and received
     * respectively.
     *
     * <p> When a socket is connected, {@link #receive receive} and
     * {@link #send send} <b>will not perform any security checks</b>
     * on incoming and outgoing packets, other than matching the packet's
     * and the socket's address and port. On a send operation, if the
     * packet's address is set and the packet's address and the socket's
     * address do not match, an {@code IllegalArgumentException} will be
     * thrown. A socket connected to a multicast address may only be used
     * to send packets.
     *
     * @param address the remote address for the socket
     *
     * @param port the remote port for the socket.
     *
     * @throws IllegalArgumentException
     *         if the address is null, or the port is out of range.
     *
     * @throws SecurityException
     *         if a security manager has been installed and it does
     *         not permit access to the given remote address
     *
     * @see #disconnect
     */
    public void connect(InetAddress address, int port) {
        try {
            connectInternal(address, port);
        } catch (SocketException se) {
            throw new Error("connect failed", se);
        }
    }

    
Connects this socket to a remote socket address (IP address + port number).

 If given an InetSocketAddress, this method behaves as if invoking connect(InetAddress,int) with the given socket addresses IP address and port number. 
Params:
  • addr –    The remote address.
Throws:
Since:1.4
/**
     * Connects this socket to a remote socket address (IP address + port number).
     *
     * <p> If given an {@link InetSocketAddress InetSocketAddress}, this method
     * behaves as if invoking {@link #connect(InetAddress,int) connect(InetAddress,int)}
     * with the given socket addresses IP address and port number.
     *
     * @param   addr    The remote address.
     *
     * @throws  SocketException
     *          if the connect fails
     *
     * @throws IllegalArgumentException
     *         if {@code addr} is {@code null}, or {@code addr} is a SocketAddress
     *         subclass not supported by this socket
     *
     * @throws SecurityException
     *         if a security manager has been installed and it does
     *         not permit access to the given remote address
     *
     * @since 1.4
     */
    public void connect(SocketAddress addr) throws SocketException {
        if (addr == null)
            throw new IllegalArgumentException("Address can't be null");
        if (!(addr instanceof InetSocketAddress))
            throw new IllegalArgumentException("Unsupported address type");
        InetSocketAddress epoint = (InetSocketAddress) addr;
        if (epoint.isUnresolved())
            throw new SocketException("Unresolved address");
        connectInternal(epoint.getAddress(), epoint.getPort());
    }

    
Disconnects the socket. If the socket is closed or not connected,
then this method has no effect.

See Also:
  • connect
/**
     * Disconnects the socket. If the socket is closed or not connected,
     * then this method has no effect.
     *
     * @see #connect
     */
    public void disconnect() {
        synchronized (this) {
            if (isClosed())
                return;
            if (connectState == ST_CONNECTED) {
                impl.disconnect ();
            }
            connectedAddress = null;
            connectedPort = -1;
            connectState = ST_NOT_CONNECTED;
            explicitFilter = false;
        }
    }

    
Returns the binding state of the socket.

 If the socket was bound prior to being closed, then this method will continue to return true after the socket is closed. 
Returns:true if the socket successfully bound to an address
Since:1.4
/**
     * Returns the binding state of the socket.
     * <p>
     * If the socket was bound prior to being {@link #close closed},
     * then this method will continue to return {@code true}
     * after the socket is closed.
     *
     * @return true if the socket successfully bound to an address
     * @since 1.4
     */
    public boolean isBound() {
        return bound;
    }

    
Returns the connection state of the socket.

 If the socket was connected prior to being closed, then this method will continue to return true after the socket is closed. 
Returns:true if the socket successfully connected to a server
Since:1.4
/**
     * Returns the connection state of the socket.
     * <p>
     * If the socket was connected prior to being {@link #close closed},
     * then this method will continue to return {@code true}
     * after the socket is closed.
     *
     * @return true if the socket successfully connected to a server
     * @since 1.4
     */
    public boolean isConnected() {
        return connectState != ST_NOT_CONNECTED;
    }

    
Returns the address to which this socket is connected. Returns null if the socket is not connected. 
 If the socket was connected prior to being closed, then this method will continue to return the connected address after the socket is closed. 
Returns:the address to which this socket is connected.
/**
     * Returns the address to which this socket is connected. Returns
     * {@code null} if the socket is not connected.
     * <p>
     * If the socket was connected prior to being {@link #close closed},
     * then this method will continue to return the connected address
     * after the socket is closed.
     *
     * @return the address to which this socket is connected.
     */
    public InetAddress getInetAddress() {
        return connectedAddress;
    }

    
Returns the port number to which this socket is connected. Returns -1 if the socket is not connected. 
 If the socket was connected prior to being closed, then this method will continue to return the connected port number after the socket is closed. 
Returns:the port number to which this socket is connected.
/**
     * Returns the port number to which this socket is connected.
     * Returns {@code -1} if the socket is not connected.
     * <p>
     * If the socket was connected prior to being {@link #close closed},
     * then this method will continue to return the connected port number
     * after the socket is closed.
     *
     * @return the port number to which this socket is connected.
     */
    public int getPort() {
        return connectedPort;
    }

    
Returns the address of the endpoint this socket is connected to, or null if it is unconnected. 
 If the socket was connected prior to being closed, then this method will continue to return the connected address after the socket is closed. 
See Also:
Returns:a SocketAddress representing the remote endpoint of this socket, or null if it is not connected yet.
Since:1.4
/**
     * Returns the address of the endpoint this socket is connected to, or
     * {@code null} if it is unconnected.
     * <p>
     * If the socket was connected prior to being {@link #close closed},
     * then this method will continue to return the connected address
     * after the socket is closed.
     *
     * @return a {@code SocketAddress} representing the remote
     *         endpoint of this socket, or {@code null} if it is
     *         not connected yet.
     * @see #getInetAddress()
     * @see #getPort()
     * @see #connect(SocketAddress)
     * @since 1.4
     */
    public SocketAddress getRemoteSocketAddress() {
        if (!isConnected())
            return null;
        return new InetSocketAddress(getInetAddress(), getPort());
    }

    
Returns the address of the endpoint this socket is bound to.

See Also:
Returns:a SocketAddress representing the local endpoint of this socket, or null if it is closed or not bound yet.
Since:1.4
/**
     * Returns the address of the endpoint this socket is bound to.
     *
     * @return a {@code SocketAddress} representing the local endpoint of this
     *         socket, or {@code null} if it is closed or not bound yet.
     * @see #getLocalAddress()
     * @see #getLocalPort()
     * @see #bind(SocketAddress)
     * @since 1.4
     */

    public SocketAddress getLocalSocketAddress() {
        if (isClosed())
            return null;
        if (!isBound())
            return null;
        return new InetSocketAddress(getLocalAddress(), getLocalPort());
    }

    
Sends a datagram packet from this socket. The DatagramPacket includes information indicating the data to be sent, its length, the IP address of the remote host, and the port number on the remote host. 
If there is a security manager, and the socket is not currently connected to a remote address, this method first performs some security checks. First, if p.getAddress().isMulticastAddress() is true, this method calls the security manager's checkMulticast method with p.getAddress() as its argument. If the evaluation of that expression is false, this method instead calls the security manager's checkConnect method with arguments p.getAddress().getHostAddress() and p.getPort(). Each call to a security manager method could result in a SecurityException if the operation is not allowed. 
Params:
  • p –  the DatagramPacket to be sent.
Throws:
  • IOException –  if an I/O error occurs.
  • SecurityException –  if a security manager exists and its checkMulticast or checkConnect method doesn't allow the send.
  • PortUnreachableException – may be thrown if the socket is connected
            to a currently unreachable destination. Note, there is no
            guarantee that the exception will be thrown.
  • IllegalBlockingModeException – 
            if this socket has an associated channel,
            and the channel is in non-blocking mode.
  • IllegalArgumentException – if the socket is connected,
            and connected address and packet address differ.
See Also:
@revised1.4
@specJSR-51
/**
     * Sends a datagram packet from this socket. The
     * {@code DatagramPacket} includes information indicating the
     * data to be sent, its length, the IP address of the remote host,
     * and the port number on the remote host.
     *
     * <p>If there is a security manager, and the socket is not currently
     * connected to a remote address, this method first performs some
     * security checks. First, if {@code p.getAddress().isMulticastAddress()}
     * is true, this method calls the
     * security manager's {@code checkMulticast} method
     * with {@code p.getAddress()} as its argument.
     * If the evaluation of that expression is false,
     * this method instead calls the security manager's
     * {@code checkConnect} method with arguments
     * {@code p.getAddress().getHostAddress()} and
     * {@code p.getPort()}. Each call to a security manager method
     * could result in a SecurityException if the operation is not allowed.
     *
     * @param      p   the {@code DatagramPacket} to be sent.
     *
     * @exception  IOException  if an I/O error occurs.
     * @exception  SecurityException  if a security manager exists and its
     *             {@code checkMulticast} or {@code checkConnect}
     *             method doesn't allow the send.
     * @exception  PortUnreachableException may be thrown if the socket is connected
     *             to a currently unreachable destination. Note, there is no
     *             guarantee that the exception will be thrown.
     * @exception  java.nio.channels.IllegalBlockingModeException
     *             if this socket has an associated channel,
     *             and the channel is in non-blocking mode.
     * @exception  IllegalArgumentException if the socket is connected,
     *             and connected address and packet address differ.
     *
     * @see        java.net.DatagramPacket
     * @see        SecurityManager#checkMulticast(InetAddress)
     * @see        SecurityManager#checkConnect
     * @revised 1.4
     * @spec JSR-51
     */
    public void send(DatagramPacket p) throws IOException  {
        InetAddress packetAddress = null;
        synchronized (p) {
            if (isClosed())
                throw new SocketException("Socket is closed");
            checkAddress (p.getAddress(), "send");
            if (connectState == ST_NOT_CONNECTED) {
                // check the address is ok wiht the security manager on every send.
                SecurityManager security = System.getSecurityManager();

                // The reason you want to synchronize on datagram packet
                // is because you don't want an applet to change the address
                // while you are trying to send the packet for example
                // after the security check but before the send.
                if (security != null) {
                    if (p.getAddress().isMulticastAddress()) {
                        security.checkMulticast(p.getAddress());
                    } else {
                        security.checkConnect(p.getAddress().getHostAddress(),
                                              p.getPort());
                    }
                }
            } else {
                // we're connected
                packetAddress = p.getAddress();
                if (packetAddress == null) {
                    p.setAddress(connectedAddress);
                    p.setPort(connectedPort);
                } else if ((!packetAddress.equals(connectedAddress)) ||
                           p.getPort() != connectedPort) {
                    throw new IllegalArgumentException("connected address " +
                                                       "and packet address" +
                                                       " differ");
                }
            }
            // Check whether the socket is bound
            if (!isBound())
                bind(new InetSocketAddress(0));
            // call the  method to send
            getImpl().send(p);
        }
    }

    
Receives a datagram packet from this socket. When this method returns, the DatagramPacket's buffer is filled with the data received. The datagram packet also contains the sender's IP address, and the port number on the sender's machine. 
 This method blocks until a datagram is received. The length field of the datagram packet object contains the length of the received message. If the message is longer than the packet's length, the message is truncated. 
 If there is a security manager, a packet cannot be received if the security manager's checkAccept method does not allow it. 
Params:
  • p –  the DatagramPacket into which to place the incoming data.
Throws:
See Also:
@revised1.4
@specJSR-51
/**
     * Receives a datagram packet from this socket. When this method
     * returns, the {@code DatagramPacket}'s buffer is filled with
     * the data received. The datagram packet also contains the sender's
     * IP address, and the port number on the sender's machine.
     * <p>
     * This method blocks until a datagram is received. The
     * {@code length} field of the datagram packet object contains
     * the length of the received message. If the message is longer than
     * the packet's length, the message is truncated.
     * <p>
     * If there is a security manager, a packet cannot be received if the
     * security manager's {@code checkAccept} method
     * does not allow it.
     *
     * @param      p   the {@code DatagramPacket} into which to place
     *                 the incoming data.
     * @exception  IOException  if an I/O error occurs.
     * @exception  SocketTimeoutException  if setSoTimeout was previously called
     *                 and the timeout has expired.
     * @exception  PortUnreachableException may be thrown if the socket is connected
     *             to a currently unreachable destination. Note, there is no guarantee that the
     *             exception will be thrown.
     * @exception  java.nio.channels.IllegalBlockingModeException
     *             if this socket has an associated channel,
     *             and the channel is in non-blocking mode.
     * @see        java.net.DatagramPacket
     * @see        java.net.DatagramSocket
     * @revised 1.4
     * @spec JSR-51
     */
    public synchronized void receive(DatagramPacket p) throws IOException {
        synchronized (p) {
            if (!isBound())
                bind(new InetSocketAddress(0));
            if (connectState == ST_NOT_CONNECTED) {
                // check the address is ok with the security manager before every recv.
                SecurityManager security = System.getSecurityManager();
                if (security != null) {
                    while(true) {
                        String peekAd = null;
                        int peekPort = 0;
                        // peek at the packet to see who it is from.
                        if (!oldImpl) {
                            // We can use the new peekData() API
                            DatagramPacket peekPacket = new DatagramPacket(new byte[1], 1);
                            peekPort = getImpl().peekData(peekPacket);
                            peekAd = peekPacket.getAddress().getHostAddress();
                        } else {
                            InetAddress adr = new InetAddress();
                            peekPort = getImpl().peek(adr);
                            peekAd = adr.getHostAddress();
                        }
                        try {
                            security.checkAccept(peekAd, peekPort);
                            // security check succeeded - so now break
                            // and recv the packet.
                            break;
                        } catch (SecurityException se) {
                            // Throw away the offending packet by consuming
                            // it in a tmp buffer.
                            DatagramPacket tmp = new DatagramPacket(new byte[1], 1);
                            getImpl().receive(tmp);

                            // silently discard the offending packet
                            // and continue: unknown/malicious
                            // entities on nets should not make
                            // runtime throw security exception and
                            // disrupt the applet by sending random
                            // datagram packets.
                            continue;
                        }
                    } // end of while
                }
            }
            DatagramPacket tmp = null;
            if ((connectState == ST_CONNECTED_NO_IMPL) || explicitFilter) {
                // We have to do the filtering the old fashioned way since
                // the native impl doesn't support connect or the connect
                // via the impl failed, or .. "explicitFilter" may be set when
                // a socket is connected via the impl, for a period of time
                // when packets from other sources might be queued on socket.
                boolean stop = false;
                while (!stop) {
                    InetAddress peekAddress = null;
                    int peekPort = -1;
                    // peek at the packet to see who it is from.
                    if (!oldImpl) {
                        // We can use the new peekData() API
                        DatagramPacket peekPacket = new DatagramPacket(new byte[1], 1);
                        peekPort = getImpl().peekData(peekPacket);
                        peekAddress = peekPacket.getAddress();
                    } else {
                        // this api only works for IPv4
                        peekAddress = new InetAddress();
                        peekPort = getImpl().peek(peekAddress);
                    }
                    if ((!connectedAddress.equals(peekAddress)) ||
                        (connectedPort != peekPort)) {
                        // throw the packet away and silently continue
                        tmp = new DatagramPacket(
                                                new byte[1024], 1024);
                        getImpl().receive(tmp);
                        if (explicitFilter) {
                            if (checkFiltering(tmp)) {
                                stop = true;
                            }
                        }
                    } else {
                        stop = true;
                    }
                }
            }
            // If the security check succeeds, or the datagram is
            // connected then receive the packet
            getImpl().receive(p);
            if (explicitFilter && tmp == null) {
                // packet was not filtered, account for it here
                checkFiltering(p);
            }
        }
    }

    private boolean checkFiltering(DatagramPacket p) throws SocketException {
        bytesLeftToFilter -= p.getLength();
        if (bytesLeftToFilter <= 0 || getImpl().dataAvailable() <= 0) {
            explicitFilter = false;
            return true;
        }
        return false;
    }

    
Gets the local address to which the socket is bound.

If there is a security manager, its checkConnect method is first called with the host address and -1 as its arguments to see if the operation is allowed. 
See Also:
Returns: the local address to which the socket is bound, null if the socket is closed, or an InetAddress representing wildcard address if either the socket is not bound, or the security manager checkConnect method does not allow the operation
Since:  1.1
/**
     * Gets the local address to which the socket is bound.
     *
     * <p>If there is a security manager, its
     * {@code checkConnect} method is first called
     * with the host address and {@code -1}
     * as its arguments to see if the operation is allowed.
     *
     * @see SecurityManager#checkConnect
     * @return  the local address to which the socket is bound,
     *          {@code null} if the socket is closed, or
     *          an {@code InetAddress} representing
     *          {@link InetAddress#isAnyLocalAddress wildcard}
     *          address if either the socket is not bound, or
     *          the security manager {@code checkConnect}
     *          method does not allow the operation
     * @since   1.1
     */
    public InetAddress getLocalAddress() {
        if (isClosed())
            return null;
        InetAddress in = null;
        try {
            in = (InetAddress) getImpl().getOption(SocketOptions.SO_BINDADDR);
            if (in.isAnyLocalAddress()) {
                in = InetAddress.anyLocalAddress();
            }
            SecurityManager s = System.getSecurityManager();
            if (s != null) {
                s.checkConnect(in.getHostAddress(), -1);
            }
        } catch (Exception e) {
            in = InetAddress.anyLocalAddress(); // "0.0.0.0"
        }
        return in;
    }

    
Returns the port number on the local host to which this socket
is bound.

Returns: the port number on the local host to which this socket is bound, -1 if the socket is closed, or 0 if it is not bound yet.
/**
     * Returns the port number on the local host to which this socket
     * is bound.
     *
     * @return  the port number on the local host to which this socket is bound,
                {@code -1} if the socket is closed, or
                {@code 0} if it is not bound yet.
     */
    public int getLocalPort() {
        if (isClosed())
            return -1;
        try {
            return getImpl().getLocalPort();
        } catch (Exception e) {
            return 0;
        }
    }

    
Enable/disable SO_TIMEOUT with the specified timeout, in
 milliseconds. With this option set to a non-zero timeout,
 a call to receive() for this DatagramSocket
 will block for only this amount of time.  If the timeout expires,
 a java.net.SocketTimeoutException is raised, though the
 DatagramSocket is still valid.  The option must be enabled prior to entering the blocking operation to have effect. The timeout must be > 0. A timeout of zero is interpreted as an infinite timeout. 
Params:
  • timeout – the specified timeout in milliseconds.
Throws:
  • SocketException – if there is an error in the underlying protocol, such as an UDP error.
See Also:
Since:  1.1
/** Enable/disable SO_TIMEOUT with the specified timeout, in
     *  milliseconds. With this option set to a non-zero timeout,
     *  a call to receive() for this DatagramSocket
     *  will block for only this amount of time.  If the timeout expires,
     *  a <B>java.net.SocketTimeoutException</B> is raised, though the
     *  DatagramSocket is still valid.  The option <B>must</B> be enabled
     *  prior to entering the blocking operation to have effect.  The
     *  timeout must be {@code > 0}.
     *  A timeout of zero is interpreted as an infinite timeout.
     *
     * @param timeout the specified timeout in milliseconds.
     * @throws SocketException if there is an error in the underlying protocol, such as an UDP error.
     * @since   1.1
     * @see #getSoTimeout()
     */
    public synchronized void setSoTimeout(int timeout) throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_TIMEOUT, timeout);
    }

    
Retrieve setting for SO_TIMEOUT.  0 returns implies that the
option is disabled (i.e., timeout of infinity).

Throws:
  • SocketException – if there is an error in the underlying protocol, such as an UDP error.
See Also:
Returns:the setting for SO_TIMEOUT
Since:  1.1
/**
     * Retrieve setting for SO_TIMEOUT.  0 returns implies that the
     * option is disabled (i.e., timeout of infinity).
     *
     * @return the setting for SO_TIMEOUT
     * @throws SocketException if there is an error in the underlying protocol, such as an UDP error.
     * @since   1.1
     * @see #setSoTimeout(int)
     */
    public synchronized int getSoTimeout() throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        if (getImpl() == null)
            return 0;
        Object o = getImpl().getOption(SocketOptions.SO_TIMEOUT);
        /* extra type safety */
        if (o instanceof Integer) {
            return ((Integer) o).intValue();
        } else {
            return 0;
        }
    }

    
Sets the SO_SNDBUF option to the specified value for this DatagramSocket. The SO_SNDBUF option is used by the network implementation as a hint to size the underlying network I/O buffers. The SO_SNDBUF setting may also be used by the network implementation to determine the maximum size of the packet that can be sent on this socket. 
 As SO_SNDBUF is a hint, applications that want to verify what size the buffer is should call getSendBufferSize(). 

Increasing the buffer size may allow multiple outgoing packets
to be queued by the network implementation when the send rate
is high.

 Note: If send(DatagramPacket) is used to send a DatagramPacket that is larger than the setting of SO_SNDBUF then it is implementation specific if the packet is sent or discarded. 
Params:
  • size – the size to which to set the send buffer
size. This value must be greater than 0.
Throws:
See Also:
/**
     * Sets the SO_SNDBUF option to the specified value for this
     * {@code DatagramSocket}. The SO_SNDBUF option is used by the
     * network implementation as a hint to size the underlying
     * network I/O buffers. The SO_SNDBUF setting may also be used
     * by the network implementation to determine the maximum size
     * of the packet that can be sent on this socket.
     * <p>
     * As SO_SNDBUF is a hint, applications that want to verify
     * what size the buffer is should call {@link #getSendBufferSize()}.
     * <p>
     * Increasing the buffer size may allow multiple outgoing packets
     * to be queued by the network implementation when the send rate
     * is high.
     * <p>
     * Note: If {@link #send(DatagramPacket)} is used to send a
     * {@code DatagramPacket} that is larger than the setting
     * of SO_SNDBUF then it is implementation specific if the
     * packet is sent or discarded.
     *
     * @param size the size to which to set the send buffer
     * size. This value must be greater than 0.
     *
     * @exception SocketException if there is an error
     * in the underlying protocol, such as an UDP error.
     * @exception IllegalArgumentException if the value is 0 or is
     * negative.
     * @see #getSendBufferSize()
     */
    public synchronized void setSendBufferSize(int size)
    throws SocketException{
        if (!(size > 0)) {
            throw new IllegalArgumentException("negative send size");
        }
        if (isClosed())
            throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_SNDBUF, size);
    }

    
Get value of the SO_SNDBUF option for this DatagramSocket, that is the buffer size used by the platform for output on this DatagramSocket. 
Throws:
  • SocketException – if there is an error in
the underlying protocol, such as an UDP error.
See Also:
Returns:the value of the SO_SNDBUF option for this DatagramSocket
/**
     * Get value of the SO_SNDBUF option for this {@code DatagramSocket}, that is the
     * buffer size used by the platform for output on this {@code DatagramSocket}.
     *
     * @return the value of the SO_SNDBUF option for this {@code DatagramSocket}
     * @exception SocketException if there is an error in
     * the underlying protocol, such as an UDP error.
     * @see #setSendBufferSize
     */
    public synchronized int getSendBufferSize() throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        int result = 0;
        Object o = getImpl().getOption(SocketOptions.SO_SNDBUF);
        if (o instanceof Integer) {
            result = ((Integer)o).intValue();
        }
        return result;
    }

    
Sets the SO_RCVBUF option to the specified value for this DatagramSocket. The SO_RCVBUF option is used by the network implementation as a hint to size the underlying network I/O buffers. The SO_RCVBUF setting may also be used by the network implementation to determine the maximum size of the packet that can be received on this socket. 
 Because SO_RCVBUF is a hint, applications that want to verify what size the buffers were set to should call getReceiveBufferSize(). 
 Increasing SO_RCVBUF may allow the network implementation to buffer multiple packets when packets arrive faster than are being received using receive(DatagramPacket). 

Note: It is implementation specific if a packet larger
than SO_RCVBUF can be received.

Params:
  • size – the size to which to set the receive buffer
size. This value must be greater than 0.
Throws:
See Also:
/**
     * Sets the SO_RCVBUF option to the specified value for this
     * {@code DatagramSocket}. The SO_RCVBUF option is used by
     * the network implementation as a hint to size the underlying
     * network I/O buffers. The SO_RCVBUF setting may also be used
     * by the network implementation to determine the maximum size
     * of the packet that can be received on this socket.
     * <p>
     * Because SO_RCVBUF is a hint, applications that want to
     * verify what size the buffers were set to should call
     * {@link #getReceiveBufferSize()}.
     * <p>
     * Increasing SO_RCVBUF may allow the network implementation
     * to buffer multiple packets when packets arrive faster than
     * are being received using {@link #receive(DatagramPacket)}.
     * <p>
     * Note: It is implementation specific if a packet larger
     * than SO_RCVBUF can be received.
     *
     * @param size the size to which to set the receive buffer
     * size. This value must be greater than 0.
     *
     * @exception SocketException if there is an error in
     * the underlying protocol, such as an UDP error.
     * @exception IllegalArgumentException if the value is 0 or is
     * negative.
     * @see #getReceiveBufferSize()
     */
    public synchronized void setReceiveBufferSize(int size)
    throws SocketException{
        if (size <= 0) {
            throw new IllegalArgumentException("invalid receive size");
        }
        if (isClosed())
            throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_RCVBUF, size);
    }

    
Get value of the SO_RCVBUF option for this DatagramSocket, that is the buffer size used by the platform for input on this DatagramSocket. 
Throws:
  • SocketException – if there is an error in the underlying protocol, such as an UDP error.
See Also:
Returns:the value of the SO_RCVBUF option for this DatagramSocket
/**
     * Get value of the SO_RCVBUF option for this {@code DatagramSocket}, that is the
     * buffer size used by the platform for input on this {@code DatagramSocket}.
     *
     * @return the value of the SO_RCVBUF option for this {@code DatagramSocket}
     * @exception SocketException if there is an error in the underlying protocol, such as an UDP error.
     * @see #setReceiveBufferSize(int)
     */
    public synchronized int getReceiveBufferSize()
    throws SocketException{
        if (isClosed())
            throw new SocketException("Socket is closed");
        int result = 0;
        Object o = getImpl().getOption(SocketOptions.SO_RCVBUF);
        if (o instanceof Integer) {
            result = ((Integer)o).intValue();
        }
        return result;
    }

    
Enable/disable the SO_REUSEADDR socket option.

 For UDP sockets it may be necessary to bind more than one socket to the same socket address. This is typically for the purpose of receiving multicast packets (See MulticastSocket). The SO_REUSEADDR socket option allows multiple sockets to be bound to the same socket address if the SO_REUSEADDR socket option is enabled prior to binding the socket using bind(SocketAddress). 
 Note: This functionality is not supported by all existing platforms, so it is implementation specific whether this option will be ignored or not. However, if it is not supported then getReuseAddress() will always return false. 
 When a DatagramSocket is created the initial setting of SO_REUSEADDR is disabled. 
 The behaviour when SO_REUSEADDR is enabled or disabled after a socket is bound (See isBound()) is not defined. 
Params:
  • on –  whether to enable or disable the
Throws:
  • SocketException – if an error occurs enabling or disabling the SO_RESUEADDR socket option, or the socket is closed.
See Also:
Since:1.4
/**
     * Enable/disable the SO_REUSEADDR socket option.
     * <p>
     * For UDP sockets it may be necessary to bind more than one
     * socket to the same socket address. This is typically for the
     * purpose of receiving multicast packets
     * (See {@link java.net.MulticastSocket}). The
     * {@code SO_REUSEADDR} socket option allows multiple
     * sockets to be bound to the same socket address if the
     * {@code SO_REUSEADDR} socket option is enabled prior
     * to binding the socket using {@link #bind(SocketAddress)}.
     * <p>
     * Note: This functionality is not supported by all existing platforms,
     * so it is implementation specific whether this option will be ignored
     * or not. However, if it is not supported then
     * {@link #getReuseAddress()} will always return {@code false}.
     * <p>
     * When a {@code DatagramSocket} is created the initial setting
     * of {@code SO_REUSEADDR} is disabled.
     * <p>
     * The behaviour when {@code SO_REUSEADDR} is enabled or
     * disabled after a socket is bound (See {@link #isBound()})
     * is not defined.
     *
     * @param on  whether to enable or disable the
     * @exception SocketException if an error occurs enabling or
     *            disabling the {@code SO_RESUEADDR} socket option,
     *            or the socket is closed.
     * @since 1.4
     * @see #getReuseAddress()
     * @see #bind(SocketAddress)
     * @see #isBound()
     * @see #isClosed()
     */
    public synchronized void setReuseAddress(boolean on) throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        // Integer instead of Boolean for compatibility with older DatagramSocketImpl
        if (oldImpl)
            getImpl().setOption(SocketOptions.SO_REUSEADDR, on?-1:0);
        else
            getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
    }

    
Tests if SO_REUSEADDR is enabled.

Throws:
  • SocketException – if there is an error
in the underlying protocol, such as an UDP error.
See Also:
Returns:a boolean indicating whether or not SO_REUSEADDR is enabled.
Since:  1.4
/**
     * Tests if SO_REUSEADDR is enabled.
     *
     * @return a {@code boolean} indicating whether or not SO_REUSEADDR is enabled.
     * @exception SocketException if there is an error
     * in the underlying protocol, such as an UDP error.
     * @since   1.4
     * @see #setReuseAddress(boolean)
     */
    public synchronized boolean getReuseAddress() throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        Object o = getImpl().getOption(SocketOptions.SO_REUSEADDR);
        return ((Boolean)o).booleanValue();
    }

    
Enable/disable SO_BROADCAST.

 Some operating systems may require that the Java virtual machine be
started with implementation specific privileges to enable this option or
send broadcast datagrams.

Params:
  • on – 
        whether or not to have broadcast turned on.
Throws:
  • SocketException – 
         if there is an error in the underlying protocol, such as an UDP
         error.
See Also:
Since:1.4
/**
     * Enable/disable SO_BROADCAST.
     *
     * <p> Some operating systems may require that the Java virtual machine be
     * started with implementation specific privileges to enable this option or
     * send broadcast datagrams.
     *
     * @param  on
     *         whether or not to have broadcast turned on.
     *
     * @throws  SocketException
     *          if there is an error in the underlying protocol, such as an UDP
     *          error.
     *
     * @since 1.4
     * @see #getBroadcast()
     */
    public synchronized void setBroadcast(boolean on) throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_BROADCAST, Boolean.valueOf(on));
    }

    
Tests if SO_BROADCAST is enabled.

Throws:
  • SocketException – if there is an error
in the underlying protocol, such as an UDP error.
See Also:
Returns:a boolean indicating whether or not SO_BROADCAST is enabled.
Since:1.4
/**
     * Tests if SO_BROADCAST is enabled.
     * @return a {@code boolean} indicating whether or not SO_BROADCAST is enabled.
     * @exception SocketException if there is an error
     * in the underlying protocol, such as an UDP error.
     * @since 1.4
     * @see #setBroadcast(boolean)
     */
    public synchronized boolean getBroadcast() throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        return ((Boolean)(getImpl().getOption(SocketOptions.SO_BROADCAST))).booleanValue();
    }

    
Sets traffic class or type-of-service octet in the IP
datagram header for datagrams sent from this DatagramSocket.
As the underlying network implementation may ignore this
value applications should consider it a hint.

 The tc must be in the range 0 <= tc <=
255 or an IllegalArgumentException will be thrown. 
Notes:

For Internet Protocol v4 the value consists of an integer, the least significant 8 bits of which represent the value of the TOS octet in IP packets sent by the socket. RFC 1349 defines the TOS values as follows: 
    

  • IPTOS_LOWCOST (0x02)
    • 

  • IPTOS_RELIABILITY (0x04)
    • 

  • IPTOS_THROUGHPUT (0x08)
    • 

  • IPTOS_LOWDELAY (0x10)
    • 


The last low order bit is always ignored as this
corresponds to the MBZ (must be zero) bit.


Setting bits in the precedence field may result in a
SocketException indicating that the operation is not
permitted.

 for Internet Protocol v6 tc is the value that would be placed into the sin6_flowinfo field of the IP header. 
Params:
  • tc –  an int value for the bitset.
Throws:
  • SocketException – if there is an error setting the
traffic class or type-of-service
See Also:
Since:1.4
/**
     * Sets traffic class or type-of-service octet in the IP
     * datagram header for datagrams sent from this DatagramSocket.
     * As the underlying network implementation may ignore this
     * value applications should consider it a hint.
     *
     * <P> The tc <B>must</B> be in the range {@code 0 <= tc <=
     * 255} or an IllegalArgumentException will be thrown.
     * <p>Notes:
     * <p>For Internet Protocol v4 the value consists of an
     * {@code integer}, the least significant 8 bits of which
     * represent the value of the TOS octet in IP packets sent by
     * the socket.
     * RFC 1349 defines the TOS values as follows:
     *
     * <UL>
     * <LI><CODE>IPTOS_LOWCOST (0x02)</CODE></LI>
     * <LI><CODE>IPTOS_RELIABILITY (0x04)</CODE></LI>
     * <LI><CODE>IPTOS_THROUGHPUT (0x08)</CODE></LI>
     * <LI><CODE>IPTOS_LOWDELAY (0x10)</CODE></LI>
     * </UL>
     * The last low order bit is always ignored as this
     * corresponds to the MBZ (must be zero) bit.
     * <p>
     * Setting bits in the precedence field may result in a
     * SocketException indicating that the operation is not
     * permitted.
     * <p>
     * for Internet Protocol v6 {@code tc} is the value that
     * would be placed into the sin6_flowinfo field of the IP header.
     *
     * @param tc        an {@code int} value for the bitset.
     * @throws SocketException if there is an error setting the
     * traffic class or type-of-service
     * @since 1.4
     * @see #getTrafficClass
     */
    public synchronized void setTrafficClass(int tc) throws SocketException {
        if (tc < 0 || tc > 255)
            throw new IllegalArgumentException("tc is not in range 0 -- 255");

        if (isClosed())
            throw new SocketException("Socket is closed");
        try {
            getImpl().setOption(SocketOptions.IP_TOS, tc);
        } catch (SocketException se) {
            // not supported if socket already connected
            // Solaris returns error in such cases
            if(!isConnected())
                throw se;
        }
    }

    
Gets traffic class or type-of-service in the IP datagram
header for packets sent from this DatagramSocket.

 As the underlying network implementation may ignore the traffic class or type-of-service set using setTrafficClass(int) this method may return a different value than was previously set using the setTrafficClass(int) method on this DatagramSocket. 
Throws:
  • SocketException – if there is an error obtaining the
traffic class or type-of-service value.
See Also:
Returns:the traffic class or type-of-service already set
Since:1.4
/**
     * Gets traffic class or type-of-service in the IP datagram
     * header for packets sent from this DatagramSocket.
     * <p>
     * As the underlying network implementation may ignore the
     * traffic class or type-of-service set using {@link #setTrafficClass(int)}
     * this method may return a different value than was previously
     * set using the {@link #setTrafficClass(int)} method on this
     * DatagramSocket.
     *
     * @return the traffic class or type-of-service already set
     * @throws SocketException if there is an error obtaining the
     * traffic class or type-of-service value.
     * @since 1.4
     * @see #setTrafficClass(int)
     */
    public synchronized int getTrafficClass() throws SocketException {
        if (isClosed())
            throw new SocketException("Socket is closed");
        return ((Integer)(getImpl().getOption(SocketOptions.IP_TOS))).intValue();
    }

    
Closes this datagram socket.

 Any thread currently blocked in receive upon this socket will throw a SocketException. 
 If this socket has an associated channel then the channel is closed
as well.

@revised1.4
@specJSR-51
/**
     * Closes this datagram socket.
     * <p>
     * Any thread currently blocked in {@link #receive} upon this socket
     * will throw a {@link SocketException}.
     *
     * <p> If this socket has an associated channel then the channel is closed
     * as well.
     *
     * @revised 1.4
     * @spec JSR-51
     */
    public void close() {
        synchronized(closeLock) {
            if (isClosed())
                return;
            impl.close();
            closed = true;
        }
    }

    
Returns whether the socket is closed or not.

Returns:true if the socket has been closed
Since:1.4
/**
     * Returns whether the socket is closed or not.
     *
     * @return true if the socket has been closed
     * @since 1.4
     */
    public boolean isClosed() {
        synchronized(closeLock) {
            return closed;
        }
    }

    
Returns the unique DatagramChannel object associated with this datagram socket, if any. 
 A datagram socket will have a channel if, and only if, the channel itself was created via the 
DatagramChannel.open method. 
Returns: the datagram channel associated with this datagram socket, or null if this socket was not created for a channel
Since:1.4
@specJSR-51
/**
     * Returns the unique {@link java.nio.channels.DatagramChannel} object
     * associated with this datagram socket, if any.
     *
     * <p> A datagram socket will have a channel if, and only if, the channel
     * itself was created via the {@link java.nio.channels.DatagramChannel#open
     * DatagramChannel.open} method.
     *
     * @return  the datagram channel associated with this datagram socket,
     *          or {@code null} if this socket was not created for a channel
     *
     * @since 1.4
     * @spec JSR-51
     */
    public DatagramChannel getChannel() {
        return null;
    }

    
User defined factory for all datagram sockets.

/**
     * User defined factory for all datagram sockets.
     */
    static DatagramSocketImplFactory factory;

    
Sets the datagram socket implementation factory for the
application. The factory can be specified only once.

 When an application creates a new datagram socket, the socket implementation factory's createDatagramSocketImpl method is called to create the actual datagram socket implementation. 
 Passing null to the method is a no-op unless the factory was already set. 
If there is a security manager, this method first calls the security manager's checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException. 
Params:
  • fac –   the desired factory.
Throws:
  • IOException –  if an I/O error occurs when setting the
             datagram socket factory.
  • SocketException –  if the factory is already defined.
  • SecurityException –  if a security manager exists and its checkSetFactory method doesn't allow the operation.
See Also:
Since:1.3
/**
     * Sets the datagram socket implementation factory for the
     * application. The factory can be specified only once.
     * <p>
     * When an application creates a new datagram socket, the socket
     * implementation factory's {@code createDatagramSocketImpl} method is
     * called to create the actual datagram socket implementation.
     * <p>
     * Passing {@code null} to the method is a no-op unless the factory
     * was already set.
     *
     * <p>If there is a security manager, this method first calls
     * the security manager's {@code checkSetFactory} method
     * to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param      fac   the desired factory.
     * @exception  IOException  if an I/O error occurs when setting the
     *              datagram socket factory.
     * @exception  SocketException  if the factory is already defined.
     * @exception  SecurityException  if a security manager exists and its
     *             {@code checkSetFactory} method doesn't allow the operation.
     * @see       java.net.DatagramSocketImplFactory#createDatagramSocketImpl()
     * @see       SecurityManager#checkSetFactory
     * @since 1.3
     */
    public static synchronized void
    setDatagramSocketImplFactory(DatagramSocketImplFactory fac)
       throws IOException
    {
        if (factory != null) {
            throw new SocketException("factory already defined");
        }
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkSetFactory();
        }
        factory = fac;
    }

    
Sets the value of a socket option.

Params:
  • name – The socket option
  • value – The value of the socket option. A value of null may be valid for some options.
Type parameters:
  • <T> – The type of the socket option value
Throws:
Returns:this DatagramSocket
Since:9
/**
     * Sets the value of a socket option.
     *
     * @param <T> The type of the socket option value
     * @param name The socket option
     * @param value The value of the socket option. A value of {@code null}
     *              may be valid for some options.
     *
     * @return this DatagramSocket
     *
     * @throws UnsupportedOperationException if the datagram socket
     *         does not support the option.
     *
     * @throws IllegalArgumentException if the value is not valid for
     *         the option.
     *
     * @throws IOException if an I/O error occurs, or if the socket is closed.
     *
     * @throws SecurityException if a security manager is set and if the socket
     *         option requires a security permission and if the caller does
     *         not have the required permission.
     *         {@link java.net.StandardSocketOptions StandardSocketOptions}
     *         do not require any security permission.
     *
     * @throws NullPointerException if name is {@code null}
     *
     * @since 9
     */
    public <T> DatagramSocket setOption(SocketOption<T> name, T value)
        throws IOException
    {
        getImpl().setOption(name, value);
        return this;
    }

    
Returns the value of a socket option.

Params:
  • name – The socket option
Type parameters:
  • <T> – The type of the socket option value
Throws:
Returns:The value of the socket option.
Since:9
/**
     * Returns the value of a socket option.
     *
     * @param <T> The type of the socket option value
     * @param name The socket option
     *
     * @return The value of the socket option.
     *
     * @throws UnsupportedOperationException if the datagram socket
     *         does not support the option.
     *
     * @throws IOException if an I/O error occurs, or if the socket is closed.
     *
     * @throws NullPointerException if name is {@code null}
     *
     * @throws SecurityException if a security manager is set and if the socket
     *         option requires a security permission and if the caller does
     *         not have the required permission.
     *         {@link java.net.StandardSocketOptions StandardSocketOptions}
     *         do not require any security permission.
     *
     * @since 9
     */
    public <T> T getOption(SocketOption<T> name) throws IOException {
        return getImpl().getOption(name);
    }

    private static Set<SocketOption<?>> options;
    private static boolean optionsSet = false;

    
Returns a set of the socket options supported by this socket.
This method will continue to return the set of options even after
the socket has been closed.

Returns:A set of the socket options supported by this socket. This set
       may be empty if the socket's DatagramSocketImpl cannot be created.
Since:9
/**
     * Returns a set of the socket options supported by this socket.
     *
     * This method will continue to return the set of options even after
     * the socket has been closed.
     *
     * @return A set of the socket options supported by this socket. This set
     *        may be empty if the socket's DatagramSocketImpl cannot be created.
     *
     * @since 9
     */
    public Set<SocketOption<?>> supportedOptions() {
        synchronized(DatagramSocket.class) {
            if (optionsSet) {
                return options;
            }
            try {
                DatagramSocketImpl impl = getImpl();
                options = Collections.unmodifiableSet(impl.supportedOptions());
            } catch (IOException e) {
                options = Collections.emptySet();
            }
            optionsSet = true;
            return options;
        }
    }
}