Java example source code file (DatagramSocket.java)
The DatagramSocket.java Java example source code/*
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*
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*
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package java.net;
import java.io.IOException;
import java.nio.channels.DatagramChannel;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
/**
* 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 JDK1.0
*/
public
class DatagramSocket implements java.io.Closeable {
/**
* 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?
*/
boolean oldImpl = false;
/*
* 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.
* <p>
* @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;
} 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
* {@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.
*
* @param impl an instance of a <B>DatagramSocketImpl
* 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.
* <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
* {@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
* {@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 JDK1.1
*/
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<Void>() {
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();
created = true;
}
/**
* 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.
* <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.
*<p>
* @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.
*
* <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
* 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).
*
* <p> If given an {@link InetSocketAddress InetSocketAddress}, this method
* behaves as if invoking {@link #connect(InetAddress,int) connect(InetAddress,int)}
* with the 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 #connect
*/
public void disconnect() {
synchronized (this) {
if (isClosed())
return;
if (connectState == ST_CONNECTED) {
impl.disconnect ();
}
connectedAddress = null;
connectedPort = -1;
connectState = ST_NOT_CONNECTED;
}
}
/**
* 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.
* <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
* {@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 {@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
* {@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.
*
* @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
* {@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 {@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
}
}
if (connectState == ST_CONNECTED_NO_IMPL) {
// 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.
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
DatagramPacket tmp = new DatagramPacket(new byte[1], 1);
getImpl().receive(tmp);
} else {
stop = true;
}
}
}
// If the security check succeeds, or the datagram is
// connected then receive the packet
getImpl().receive(p);
}
}
/**
* 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.
*
* @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 <B>java.net.SocketTimeoutException is raised, though the
* DatagramSocket is still valid. The option <B>must 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 JDK1.1
* @see #getSoTimeout()
*/
public synchronized void setSoTimeout(int timeout) throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
}
/**
* 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 JDK1.1
* @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
* {@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, new Integer(size));
}
/**
* 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
* {@code DatagramSocket}. The SO_RCVBUF option is used by the
* 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, new Integer(size));
}
/**
* 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.
* <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, new Integer(on?-1:0));
else
getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
}
/**
* 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.
*
* <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.
* @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.
*
* <P> The tc must 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>
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