public class DatagramSocket extends Object implements Closeable
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.
DatagramPacket, 
DatagramChannel| Modifier | Constructor and Description | 
|---|---|
|   | DatagramSocket()Constructs a datagram socket and binds it to any available port
 on the local host machine. | 
| protected  | DatagramSocket(DatagramSocketImpl impl)Creates an unbound datagram socket with the specified
 DatagramSocketImpl. | 
|   | 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. | 
|   | DatagramSocket(SocketAddress bindaddr)Creates a datagram socket, bound to the specified local
 socket address. | 
| Modifier and Type | Method and Description | 
|---|---|
| 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  DatagramChannelobject
 associated with this datagram socket, if any. | 
| 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. | 
| int | getPort()Returns the port number to which this socket is connected. | 
| int | getReceiveBufferSize()Get value of the SO_RCVBUF option for this  DatagramSocket, that is the
 buffer size used by the platform for input on thisDatagramSocket. | 
| SocketAddress | getRemoteSocketAddress()Returns the address of the endpoint this socket is connected to, or
  nullif it is unconnected. | 
| boolean | getReuseAddress()Tests if SO_REUSEADDR is enabled. | 
| int | getSendBufferSize()Get value of the SO_SNDBUF option for this  DatagramSocket, that is the
 buffer size used by the platform for output on thisDatagramSocket. | 
| 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. | 
| void | setReceiveBufferSize(int size)Sets the SO_RCVBUF option to the specified value for this
  DatagramSocket. | 
| 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
  DatagramSocket. | 
| 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. | 
public DatagramSocket()
               throws SocketException
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.
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.SecurityManager.checkListen(int)protected DatagramSocket(DatagramSocketImpl impl)
impl - an instance of a DatagramSocketImpl
        the subclass wishes to use on the DatagramSocket.public DatagramSocket(SocketAddress bindaddr) throws SocketException
 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.
bindaddr - local socket address to bind, or null
                 for an unbound socket.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.SecurityManager.checkListen(int)public DatagramSocket(int port)
               throws SocketException
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.
port - port to use.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.SecurityManager.checkListen(int)public DatagramSocket(int port,
                      InetAddress laddr)
               throws SocketException
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.
port - local port to useladdr - local address to bindSocketException - 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.SecurityManager.checkListen(int)public void bind(SocketAddress addr) throws SocketException
 If the address is null, then the system will pick up
 an ephemeral port and a valid local address to bind the socket.
addr - The address and port to bind to.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.public void connect(InetAddress address, int port)
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.
address - the remote address for the socketport - the remote port for the socket.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 addressdisconnect()public void connect(SocketAddress addr) throws SocketException
 If given an InetSocketAddress, this method
 behaves as if invoking connect(InetAddress,int)
 with the the given socket addresses IP address and port number.
addr - The remote address.SocketException - if the connect failsIllegalArgumentException - if addr is null, or addr is a SocketAddress
         subclass not supported by this socketSecurityException - if a security manager has been installed and it does
         not permit access to the given remote addresspublic void disconnect()
connect(java.net.InetAddress, int)public boolean isBound()
 If the socket was bound prior to being closed,
 then this method will continue to return true
 after the socket is closed.
public boolean isConnected()
 If the socket was connected prior to being closed,
 then this method will continue to return true
 after the socket is closed.
public InetAddress getInetAddress()
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.
public int getPort()
-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.
public SocketAddress getRemoteSocketAddress()
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.
SocketAddress representing the remote
         endpoint of this socket, or null if it is
         not connected yet.getInetAddress(), 
getPort(), 
connect(SocketAddress)public SocketAddress getLocalSocketAddress()
SocketAddress representing the local endpoint of this
         socket, or null if it is closed or not bound yet.getLocalAddress(), 
getLocalPort(), 
bind(SocketAddress)public void send(DatagramPacket p) throws IOException
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.
p - the DatagramPacket to be sent.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.DatagramPacket, 
SecurityManager.checkMulticast(InetAddress), 
SecurityManager.checkConnect(java.lang.String, int)public void receive(DatagramPacket p) throws IOException
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.
p - the DatagramPacket into which to place
                 the incoming data.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.DatagramPacket, 
DatagramSocketpublic InetAddress getLocalAddress()
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.
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 operationSecurityManager.checkConnect(java.lang.String, int)public int getLocalPort()
-1 if the socket is closed, or
                0 if it is not bound yet.public void setSoTimeout(int timeout)
                  throws SocketException
> 0.
  A timeout of zero is interpreted as an infinite timeout.timeout - the specified timeout in milliseconds.SocketException - if there is an error in the underlying protocol, such as an UDP error.getSoTimeout()public int getSoTimeout()
                 throws SocketException
SocketException - if there is an error in the underlying protocol, such as an UDP error.setSoTimeout(int)public void setSendBufferSize(int size)
                       throws SocketException
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.
size - the size to which to set the send buffer
 size. This value must be greater than 0.SocketException - if there is an error
 in the underlying protocol, such as an UDP error.IllegalArgumentException - if the value is 0 or is
 negative.getSendBufferSize()public int getSendBufferSize()
                      throws SocketException
DatagramSocket, that is the
 buffer size used by the platform for output on this DatagramSocket.DatagramSocketSocketException - if there is an error in
 the underlying protocol, such as an UDP error.setSendBufferSize(int)public void setReceiveBufferSize(int size)
                          throws SocketException
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.
 
 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.
size - the size to which to set the receive buffer
 size. This value must be greater than 0.SocketException - if there is an error in
 the underlying protocol, such as an UDP error.IllegalArgumentException - if the value is 0 or is
 negative.getReceiveBufferSize()public int getReceiveBufferSize()
                         throws SocketException
DatagramSocket, that is the
 buffer size used by the platform for input on this DatagramSocket.DatagramSocketSocketException - if there is an error in the underlying protocol, such as an UDP error.setReceiveBufferSize(int)public void setReuseAddress(boolean on)
                     throws SocketException
 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.
on - whether to enable or disable theSocketException - if an error occurs enabling or
            disabling the SO_RESUEADDR socket option,
            or the socket is closed.getReuseAddress(), 
bind(SocketAddress), 
isBound(), 
isClosed()public boolean getReuseAddress()
                        throws SocketException
boolean indicating whether or not SO_REUSEADDR is enabled.SocketException - if there is an error
 in the underlying protocol, such as an UDP error.setReuseAddress(boolean)public void setBroadcast(boolean on)
                  throws SocketException
Some operating systems may require that the Java virtual machine be started with implementation specific privileges to enable this option or send broadcast datagrams.
on - whether or not to have broadcast turned on.SocketException - if there is an error in the underlying protocol, such as an UDP
          error.getBroadcast()public boolean getBroadcast()
                     throws SocketException
boolean indicating whether or not SO_BROADCAST is enabled.SocketException - if there is an error
 in the underlying protocol, such as an UDP error.setBroadcast(boolean)public void setTrafficClass(int tc)
                     throws SocketException
 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.
tc - an int value for the bitset.SocketException - if there is an error setting the
 traffic class or type-of-servicegetTrafficClass()public int getTrafficClass()
                    throws SocketException
 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.
SocketException - if there is an error obtaining the
 traffic class or type-of-service value.setTrafficClass(int)public void close()
 Any thread currently blocked in receive(java.net.DatagramPacket) upon this socket
 will throw a SocketException.
 
If this socket has an associated channel then the channel is closed as well.
close in interface Closeableclose in interface AutoCloseablepublic boolean isClosed()
public DatagramChannel getChannel()
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.
null if this socket was not created for a channelpublic static void setDatagramSocketImplFactory(DatagramSocketImplFactory fac) throws IOException
 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.
fac - the desired factory.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.DatagramSocketImplFactory.createDatagramSocketImpl(), 
SecurityManager.checkSetFactory() Submit a bug or feature 
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