DatagramSocket
public
class
DatagramSocket
extends Object
implements
Closeable
java.lang.Object | |
↳ | java.net.DatagramSocket |
|
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.
See also:
Summary
Public constructors | |
---|---|
DatagramSocket()
Constructs a datagram socket and binds it to any available port on the local host machine. |
|
DatagramSocket(SocketAddress bindaddr)
Creates a datagram socket, bound to the specified local socket address. |
|
DatagramSocket(int port)
Constructs a datagram socket and binds it to the specified port on the local host machine. |
|
DatagramSocket(int port, InetAddress laddr)
Creates a datagram socket, bound to the specified local address. |
Protected constructors | |
---|---|
DatagramSocket(DatagramSocketImpl impl)
Creates an unbound datagram socket with the specified DatagramSocketImpl. |
Public methods | |
---|---|
void
|
bind(SocketAddress addr)
Binds this DatagramSocket to a specific address and port. |
void
|
close()
Closes this datagram socket. |
void
|
connect(InetAddress address, int port)
Connects the socket to a remote address for this socket. |
void
|
connect(SocketAddress addr)
Connects this socket to a remote socket address (IP address + port number). |
void
|
disconnect()
Disconnects the socket. |
boolean
|
getBroadcast()
Tests if SO_BROADCAST is enabled. |
DatagramChannel
|
getChannel()
Returns the unique |
InetAddress
|
getInetAddress()
Returns the address to which this socket is connected. |
InetAddress
|
getLocalAddress()
Gets the local address to which the socket is bound. |
int
|
getLocalPort()
Returns the port number on the local host to which this socket is bound. |
SocketAddress
|
getLocalSocketAddress()
Returns the address of the endpoint this socket is bound to. |
<T>
T
|
getOption(SocketOption<T> name)
Returns the value of a socket option. |
int
|
getPort()
Returns the port number to which this socket is connected. |
int
|
getReceiveBufferSize()
Get value of the SO_RCVBUF option for this |
SocketAddress
|
getRemoteSocketAddress()
Returns the address of the endpoint this socket is connected to, or
|
boolean
|
getReuseAddress()
Tests if SO_REUSEADDR is enabled. |
int
|
getSendBufferSize()
Get value of the SO_SNDBUF option for this |
int
|
getSoTimeout()
Retrieve setting for SO_TIMEOUT. |
int
|
getTrafficClass()
Gets traffic class or type-of-service in the IP datagram header for packets sent from this DatagramSocket. |
boolean
|
isBound()
Returns the binding state of the socket. |
boolean
|
isClosed()
Returns whether the socket is closed or not. |
boolean
|
isConnected()
Returns the connection state of the socket. |
void
|
receive(DatagramPacket p)
Receives a datagram packet from this socket. |
void
|
send(DatagramPacket p)
Sends a datagram packet from this socket. |
void
|
setBroadcast(boolean on)
Enable/disable SO_BROADCAST. |
static
void
|
setDatagramSocketImplFactory(DatagramSocketImplFactory fac)
Sets the datagram socket implementation factory for the application. |
<T>
DatagramSocket
|
setOption(SocketOption<T> name, T value)
Sets the value of a socket option. |
void
|
setReceiveBufferSize(int size)
Sets the SO_RCVBUF option to the specified value for this
|
void
|
setReuseAddress(boolean on)
Enable/disable the SO_REUSEADDR socket option. |
void
|
setSendBufferSize(int size)
Sets the SO_SNDBUF option to the specified value for this
|
void
|
setSoTimeout(int timeout)
Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. |
void
|
setTrafficClass(int tc)
Sets traffic class or type-of-service octet in the IP datagram header for datagrams sent from this DatagramSocket. |
Set<SocketOption<?>>
|
supportedOptions()
Returns a set of the socket options supported by this socket. |
Inherited methods | |||||||||||||||||||||||
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Public constructors
DatagramSocket
public DatagramSocket ()
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:
DatagramSocket
public DatagramSocket (SocketAddress bindaddr)
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.
Parameters | |
---|---|
bindaddr |
SocketAddress : 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:
DatagramSocket
public DatagramSocket (int port)
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.
Parameters | |
---|---|
port |
int : 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:
DatagramSocket
public DatagramSocket (int port, InetAddress laddr)
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.
Parameters | |
---|---|
port |
int : local port to use |
laddr |
InetAddress : 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:
Protected constructors
DatagramSocket
protected DatagramSocket (DatagramSocketImpl impl)
Creates an unbound datagram socket with the specified DatagramSocketImpl.
Parameters | |
---|---|
impl |
DatagramSocketImpl : an instance of a DatagramSocketImpl
the subclass wishes to use on the DatagramSocket. |
Public methods
bind
public void bind (SocketAddress addr)
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.
Parameters | |
---|---|
addr |
SocketAddress : 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. |
close
public void close ()
Closes this datagram socket.
Any thread currently blocked in receive(DatagramPacket)
upon this socket
will throw a SocketException
.
If this socket has an associated channel then the channel is closed as well.
connect
public void connect (InetAddress address, int port)
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.
Parameters | |
---|---|
address |
InetAddress : the remote address for the socket |
port |
int : the remote port for the socket. |
Throws | |
---|---|
IllegalArgumentException |
if the address is null, or the port is out of range. |
SecurityException |
if a security manager has been installed and it does not permit access to the given remote address |
See also:
connect
public void connect (SocketAddress addr)
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.
Parameters | |
---|---|
addr |
SocketAddress : The remote address. |
Throws | |
---|---|
SocketException |
if the connect fails |
IllegalArgumentException |
if addr is null , or addr is a SocketAddress
subclass not supported by this socket |
SecurityException |
if a security manager has been installed and it does not permit access to the given remote address |
disconnect
public void disconnect ()
Disconnects the socket. If the socket is closed or not connected, then this method has no effect.
See also:
getBroadcast
public boolean getBroadcast ()
Tests if SO_BROADCAST is enabled.
Returns | |
---|---|
boolean |
a boolean indicating whether or not SO_BROADCAST is enabled. |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
See also:
getChannel
public DatagramChannel getChannel ()
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 | |
---|---|
DatagramChannel |
the datagram channel associated with this datagram socket,
or null if this socket was not created for a channel |
getInetAddress
public InetAddress getInetAddress ()
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 | |
---|---|
InetAddress |
the address to which this socket is connected. |
getLocalAddress
public InetAddress getLocalAddress ()
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.
Returns | |
---|---|
InetAddress |
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 |
getLocalPort
public int getLocalPort ()
Returns the port number on the local host to which this socket is bound.
Returns | |
---|---|
int |
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. |
getLocalSocketAddress
public SocketAddress getLocalSocketAddress ()
Returns the address of the endpoint this socket is bound to.
Returns | |
---|---|
SocketAddress |
a SocketAddress representing the local endpoint of this
socket, or null if it is closed or not bound yet. |
getOption
public T getOption (SocketOption<T> name)
Returns the value of a socket option.
Parameters | |
---|---|
name |
SocketOption : The socket option |
Returns | |
---|---|
T |
The value of the socket option. |
Throws | |
---|---|
UnsupportedOperationException |
if the datagram socket does not support the option. |
IOException |
if an I/O error occurs, or if the socket is closed. |
NullPointerException |
if name is null |
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.
StandardSocketOptions
do not require any security permission. |
getPort
public int getPort ()
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 | |
---|---|
int |
the port number to which this socket is connected. |
getReceiveBufferSize
public int getReceiveBufferSize ()
Get value of the SO_RCVBUF option for this DatagramSocket
, that is the
buffer size used by the platform for input on this DatagramSocket
.
Returns | |
---|---|
int |
the value of the SO_RCVBUF option for this DatagramSocket |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
See also:
getRemoteSocketAddress
public SocketAddress getRemoteSocketAddress ()
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.
Returns | |
---|---|
SocketAddress |
a SocketAddress representing the remote
endpoint of this socket, or null if it is
not connected yet. |
getReuseAddress
public boolean getReuseAddress ()
Tests if SO_REUSEADDR is enabled.
Returns | |
---|---|
boolean |
a boolean indicating whether or not SO_REUSEADDR is enabled. |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
See also:
getSendBufferSize
public int getSendBufferSize ()
Get value of the SO_SNDBUF option for this DatagramSocket
, that is the
buffer size used by the platform for output on this DatagramSocket
.
Returns | |
---|---|
int |
the value of the SO_SNDBUF option for this DatagramSocket |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
See also:
getSoTimeout
public int getSoTimeout ()
Retrieve setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).
Returns | |
---|---|
int |
the setting for SO_TIMEOUT |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
See also:
getTrafficClass
public int getTrafficClass ()
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.
Returns | |
---|---|
int |
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. |
See also:
isBound
public boolean isBound ()
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 | |
---|---|
boolean |
true if the socket successfully bound to an address |
isClosed
public boolean isClosed ()
Returns whether the socket is closed or not.
Returns | |
---|---|
boolean |
true if the socket has been closed |
isConnected
public boolean isConnected ()
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 | |
---|---|
boolean |
true if the socket successfully connected to a server |
receive
public void receive (DatagramPacket 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.
Parameters | |
---|---|
p |
DatagramPacket : the DatagramPacket into which to place
the incoming data. |
Throws | |
---|---|
IOException |
if an I/O error occurs. |
SocketTimeoutException |
if setSoTimeout was previously called and the timeout has expired. |
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. |
See also:
send
public void send (DatagramPacket p)
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.
Parameters | |
---|---|
p |
DatagramPacket : 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. |
setBroadcast
public void setBroadcast (boolean on)
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.
Parameters | |
---|---|
on |
boolean : 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:
setDatagramSocketImplFactory
public static void setDatagramSocketImplFactory (DatagramSocketImplFactory fac)
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.
Parameters | |
---|---|
fac |
DatagramSocketImplFactory : 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. |
setOption
public DatagramSocket setOption (SocketOption<T> name, T value)
Sets the value of a socket option.
Parameters | |
---|---|
name |
SocketOption : The socket option |
value |
T : The value of the socket option. A value of null
may be valid for some options. |
Returns | |
---|---|
DatagramSocket |
this DatagramSocket |
Throws | |
---|---|
UnsupportedOperationException |
if the datagram socket does not support the option. |
IllegalArgumentException |
if the value is not valid for the option. |
IOException |
if an I/O error occurs, or if the socket is closed. |
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.
StandardSocketOptions
do not require any security permission. |
NullPointerException |
if name is null |
setReceiveBufferSize
public void setReceiveBufferSize (int size)
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(java.net.DatagramPacket)
.
Note: It is implementation specific if a packet larger than SO_RCVBUF can be received.
Parameters | |
---|---|
size |
int : the size to which to set the receive buffer
size. This value must be greater than 0. |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
IllegalArgumentException |
if the value is 0 or is negative. |
See also:
setReuseAddress
public void setReuseAddress (boolean on)
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(java.net.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.
Parameters | |
---|---|
on |
boolean : 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. |
setSendBufferSize
public void setSendBufferSize (int size)
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(java.net.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.
Parameters | |
---|---|
size |
int : the size to which to set the send buffer
size. This value must be greater than 0. |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
IllegalArgumentException |
if the value is 0 or is negative. |
See also:
setSoTimeout
public void setSoTimeout (int timeout)
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.
Parameters | |
---|---|
timeout |
int : the specified timeout in milliseconds. |
Throws | |
---|---|
SocketException |
if there is an error in the underlying protocol, such as an UDP error. |
See also:
setTrafficClass
public void setTrafficClass (int tc)
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)
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.
Parameters | |
---|---|
tc |
int : an int value for the bitset. |
Throws | |
---|---|
SocketException |
if there is an error setting the traffic class or type-of-service |
See also:
supportedOptions
public Set<SocketOption<?>> supportedOptions ()
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 | |
---|---|
Set<SocketOption<?>> |
A set of the socket options supported by this socket. This set may be empty if the socket's DatagramSocketImpl cannot be created. |