- java.lang.Object
-
- java.net.DatagramSocket
-
- All Implemented Interfaces:
- Closeable, AutoCloseable
- Direct Known Subclasses:
- MulticastSocket
public class DatagramSocket extends Object implements Closeable
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 theSO_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.- Since:
- JDK1.0
- See Also:
DatagramPacket
,DatagramChannel
-
-
Constructor Summary
Constructors 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.
-
Method Summary
Methods Modifier and Type Method and Description void
bind(SocketAddress addr)
Binds this DatagramSocket to a specific address & 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 uniqueDatagramChannel
object 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 this DatagramSocket.SocketAddress
getRemoteSocketAddress()
Returns the address of the endpoint this socket is connected to, ornull
if 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 this DatagramSocket.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.
-
-
-
Constructor Detail
-
DatagramSocket
public DatagramSocket() throws SocketException
Constructs a datagram socket and binds it to any available port on the local host machine. The socket will be bound to thewildcard
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 itscheckListen
method doesn't allow the operation.- See Also:
SecurityManager.checkListen(int)
-
DatagramSocket
protected DatagramSocket(DatagramSocketImpl impl)
Creates an unbound datagram socket with the specified DatagramSocketImpl.- Parameters:
impl
- an instance of a DatagramSocketImpl the subclass wishes to use on the DatagramSocket.- Since:
- 1.4
-
DatagramSocket
public DatagramSocket(SocketAddress bindaddr) throws SocketException
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
- local socket address to bind, ornull
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 itscheckListen
method doesn't allow the operation.- Since:
- 1.4
- See Also:
SecurityManager.checkListen(int)
-
DatagramSocket
public DatagramSocket(int port) throws SocketException
Constructs a datagram socket and binds it to the specified port on the local host machine. The socket will be bound to thewildcard
address, an IP address chosen by the kernel.If there is a security manager, its
checkListen
method is first called with theport
argument as its argument to ensure the operation is allowed. This could result in a SecurityException.- Parameters:
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 itscheckListen
method doesn't allow the operation.- See Also:
SecurityManager.checkListen(int)
-
DatagramSocket
public DatagramSocket(int port, InetAddress laddr) throws SocketException
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 thewildcard
address, an IP address chosen by the kernel.If there is a security manager, its
checkListen
method is first called with theport
argument as its argument to ensure the operation is allowed. This could result in a SecurityException.- Parameters:
port
- local port to useladdr
- 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 itscheckListen
method doesn't allow the operation.- Since:
- JDK1.1
- See Also:
SecurityManager.checkListen(int)
-
-
Method Detail
-
bind
public void bind(SocketAddress addr) throws SocketException
Binds this DatagramSocket to a specific address & 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
- The address & 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 itscheckListen
method doesn't allow the operation.IllegalArgumentException
- if addr is a SocketAddress subclass not supported by this socket.- Since:
- 1.4
-
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 amulticast address
, the security manager'scheckMulticast
method is invoked with the givenaddress
. Otherwise, the security manager'scheckConnect
andcheckAccept
methods are invoked, with the givenaddress
andport
, to verify that datagrams are permitted to be sent and received respectively.When a socket is connected,
receive
andsend
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, anIllegalArgumentException
will be thrown. A socket connected to a multicast address may only be used to send packets.- Parameters:
address
- the remote address for the socketport
- 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:
disconnect()
-
connect
public void connect(SocketAddress addr) throws SocketException
Connects this socket to a remote socket address (IP address + port number).If given an
InetSocketAddress
, this method behaves as if invokingconnect(InetAddress,int)
with the the given socket addresses IP address and port number.- Parameters:
addr
- The remote address.- Throws:
SocketException
- if the connect failsIllegalArgumentException
- ifaddr
isnull
, oraddr
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 address- Since:
- 1.4
-
disconnect
public void disconnect()
Disconnects the socket. If the socket is closed or not connected, then this method has no effect.- See Also:
connect(java.net.InetAddress, int)
-
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 returntrue
after the socket is closed.- Returns:
- true if the socket successfully bound to an address
- Since:
- 1.4
-
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 returntrue
after the socket is closed.- Returns:
- true if the socket successfully connected to a server
- Since:
- 1.4
-
getInetAddress
public InetAddress getInetAddress()
Returns the address to which this socket is connected. Returnsnull
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.
-
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:
- the port number to which this socket is connected.
-
getRemoteSocketAddress
public SocketAddress getRemoteSocketAddress()
Returns the address of the endpoint this socket is connected to, ornull
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:
- a
SocketAddress
representing the remote endpoint of this socket, ornull
if it is not connected yet. - Since:
- 1.4
- See Also:
getInetAddress()
,getPort()
,connect(SocketAddress)
-
getLocalSocketAddress
public SocketAddress getLocalSocketAddress()
Returns the address of the endpoint this socket is bound to.- Returns:
- a
SocketAddress
representing the local endpoint of this socket, ornull
if it is closed or not bound yet. - Since:
- 1.4
- See Also:
getLocalAddress()
,getLocalPort()
,bind(SocketAddress)
-
send
public void send(DatagramPacket p) throws IOException
Sends a datagram packet from this socket. TheDatagramPacket
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'scheckMulticast
method withp.getAddress()
as its argument. If the evaluation of that expression is false, this method instead calls the security manager'scheckConnect
method with argumentsp.getAddress().getHostAddress()
andp.getPort()
. Each call to a security manager method could result in a SecurityException if the operation is not allowed.- Parameters:
p
- theDatagramPacket
to be sent.- Throws:
IOException
- if an I/O error occurs.SecurityException
- if a security manager exists and itscheckMulticast
orcheckConnect
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:
DatagramPacket
,SecurityManager.checkMulticast(InetAddress)
,SecurityManager.checkConnect(java.lang.String, int)
-
receive
public void receive(DatagramPacket p) throws IOException
Receives a datagram packet from this socket. When this method returns, theDatagramPacket
'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
- theDatagramPacket
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:
DatagramPacket
,DatagramSocket
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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:
- the local address to which the socket is bound,
null
if the socket is closed, or anInetAddress
representingwildcard
address if either the socket is not bound, or the security managercheckConnect
method does not allow the operation - Since:
- 1.1
- See Also:
SecurityManager.checkConnect(java.lang.String, int)
-
getLocalPort
public int getLocalPort()
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, or0
if it is not bound yet.
-
setSoTimeout
public void setSoTimeout(int timeout) throws SocketException
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
- 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 Also:
getSoTimeout()
-
getSoTimeout
public int getSoTimeout() throws SocketException
Retrieve setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).- Returns:
- 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 Also:
setSoTimeout(int)
-
setSendBufferSize
public void setSendBufferSize(int size) throws SocketException
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 aDatagramPacket
that is larger than the setting of SO_SNDBUF then it is implementation specific if the packet is sent or discarded.- Parameters:
size
- 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:
getSendBufferSize()
-
getSendBufferSize
public int getSendBufferSize() throws SocketException
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:
- 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:
setSendBufferSize(int)
-
setReceiveBufferSize
public void setReceiveBufferSize(int size) throws SocketException
Sets the SO_RCVBUF option to the specified value for this 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.
- Parameters:
size
- 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:
getReceiveBufferSize()
-
getReceiveBufferSize
public int getReceiveBufferSize() throws SocketException
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:
- 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:
setReceiveBufferSize(int)
-
setReuseAddress
public void setReuseAddress(boolean on) throws SocketException
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 usingbind(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 returnfalse
.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
- 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.- Since:
- 1.4
- See Also:
getReuseAddress()
,bind(SocketAddress)
,isBound()
,isClosed()
-
getReuseAddress
public boolean getReuseAddress() throws SocketException
Tests if SO_REUSEADDR is enabled.- Returns:
- 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.- Since:
- 1.4
- See Also:
setReuseAddress(boolean)
-
setBroadcast
public void setBroadcast(boolean on) throws SocketException
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
- 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 Also:
getBroadcast()
-
getBroadcast
public boolean getBroadcast() throws SocketException
Tests if SO_BROADCAST is enabled.- Returns:
- 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.- Since:
- 1.4
- See Also:
setBroadcast(boolean)
-
setTrafficClass
public void setTrafficClass(int tc) throws SocketException
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
- anint
value for the bitset.- Throws:
SocketException
- if there is an error setting the traffic class or type-of-service- Since:
- 1.4
- See Also:
getTrafficClass()
-
getTrafficClass
public int getTrafficClass() throws SocketException
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 thesetTrafficClass(int)
method on this DatagramSocket.- Returns:
- 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 Also:
setTrafficClass(int)
-
close
public void close()
Closes this datagram socket.Any thread currently blocked in
receive(java.net.DatagramPacket)
upon this socket will throw aSocketException
.If this socket has an associated channel then the channel is closed as well.
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in interfaceAutoCloseable
-
isClosed
public boolean isClosed()
Returns whether the socket is closed or not.- Returns:
- true if the socket has been closed
- Since:
- 1.4
-
getChannel
public DatagramChannel getChannel()
Returns the uniqueDatagramChannel
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
-
setDatagramSocketImplFactory
public static void setDatagramSocketImplFactory(DatagramSocketImplFactory fac) throws IOException
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
- 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 itscheckSetFactory
method doesn't allow the operation.- Since:
- 1.3
- See Also:
DatagramSocketImplFactory.createDatagramSocketImpl()
,SecurityManager.checkSetFactory()
-
-
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