Closeable
, AutoCloseable
MulticastSocket
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. The DatagramSocket
class defines convenience methods to set and get several socket options. This class also defines the setOption
and getOption
methods to set and query socket options. A DatagramSocket
supports the following socket options:
Option Name Description SO_SNDBUF
The size of the socket send buffer in bytes SO_RCVBUF
The size of the socket receive buffer in bytes SO_REUSEADDR
Re-use address SO_BROADCAST
Allow transmission of broadcast datagrams IP_TOS
The Type of Service (ToS) octet in the Internet Protocol (IP) header
In addition, the DatagramSocket
class defines methods to join and leave a multicast group, and supports multicast options which are useful when joining, leaving, or sending datagrams to a multicast group. The following multicast options are supported:
An implementation may also support additional options.
Option Name Description IP_MULTICAST_IF
The network interface for Internet Protocol (IP) multicast datagrams IP_MULTICAST_TTL
The time-to-live for Internet Protocol (IP) multicast datagrams IP_MULTICAST_LOOP
Loopback for Internet Protocol (IP) multicast datagrams
DatagramChannel
implements the MulticastChannel
interface and provides an alternative API for sending and receiving multicast datagrams. The MulticastChannel
API supports both any-source and source-specific multicast. Consider using DatagramChannel
for multicasting.
DatagramSocket
can be used directly for multicasting. However, contrarily to MulticastSocket
, DatagramSocket
doesn't call the setReuseAddress(boolean)
method to enable the SO_REUSEADDR socket option by default. If creating a DatagramSocket
intended to later join a multicast group, the caller should consider explicitly enabling the SO_REUSEADDR option.
An instance of DatagramSocket
can be used to send or receive multicast datagram packets. It is not necessary to join a multicast group in order to send multicast datagrams. Before sending out multicast datagram packets however, the default outgoing interface for sending multicast datagram should first be configured using setOption
and StandardSocketOptions.IP_MULTICAST_IF
:
DatagramSocket sender = new DatagramSocket(new InetSocketAddress(0));
NetworkInterface outgoingIf = NetworkInterface.getByName("en0");
sender.setOption(StandardSocketOptions.IP_MULTICAST_IF, outgoingIf);
// optionally configure multicast TTL; the TTL defines the scope of a
// multicast datagram, for example, confining it to host local (0) or
// link local (1) etc...
int ttl = ...; // a number between 0 and 255
sender.setOption(StandardSocketOptions.IP_MULTICAST_TTL, ttl);
// send a packet to a multicast group
byte[] msgBytes = ...;
InetAddress mcastaddr = InetAddress.getByName("228.5.6.7");
int port = 6789;
InetSocketAddress dest = new InetSocketAddress(mcastaddr, port);
DatagramPacket hi = new DatagramPacket(msgBytes, msgBytes.length, dest);
sender.send(hi);
An instance of DatagramSocket
can also be used to receive multicast datagram packets. A DatagramSocket
that is created with the intent of receiving multicast datagrams should be created unbound. Before binding the socket, setReuseAddress(true)
should be configured:
DatagramSocket socket = new DatagramSocket(null); // unbound
socket.setReuseAddress(true); // set reuse address before binding
socket.bind(new InetSocketAddress(6789)); // bind
// joinGroup 228.5.6.7
InetAddress mcastaddr = InetAddress.getByName("228.5.6.7");
InetSocketAddress group = new InetSocketAddress(mcastaddr, 0);
NetworkInterface netIf = NetworkInterface.getByName("en0");
socket.joinGroup(group, netIf);
byte[] msgBytes = new byte[1024]; // up to 1024 bytes
DatagramPacket packet = new DatagramPacket(msgBytes, msgBytes.length);
socket.receive(packet);
....
// eventually leave group
socket.leaveGroup(group, netIf);
Platform dependencies
The multicast implementation is intended to map directly to the native multicasting facility. Consequently, the following items should be considered when developing an application that receives IP multicast datagrams:
DatagramChannel
, the constructors of DatagramSocket
do not allow to specify the ProtocolFamily
of the underlying socket. Consequently, the protocol family of the underlying socket may not correspond to the protocol family of the multicast groups that the DatagramSocket
will attempt to join. DatagramSocket
with an underlying socket created in one protocol family can join and receive multicast datagrams when the address of the multicast group corresponds to another protocol family. For example, it is implementation specific if a DatagramSocket
to an IPv6 socket can join an IPv4 multicast group and receive multicast datagrams sent to the group. DatagramSocket
should be bound to the wildcard address. If the socket is bound to a specific address, rather than the wildcard address then it is implementation specific if multicast datagrams are received by the socket. Modifier | Constructor | Description |
---|---|---|
Constructs a datagram socket and binds it to any available port on the local host machine. |
||
Constructs a datagram socket and binds it to the specified port on the local host machine. |
||
Creates a datagram socket, bound to the specified local address. |
||
protected |
Creates an unbound datagram socket with the specified DatagramSocketImpl. |
|
Creates a datagram socket, bound to the specified local socket address. |
Modifier and Type | Method | Description |
---|---|---|
void |
bind |
Binds this DatagramSocket to a specific address and port. |
void |
close() |
Closes this datagram socket. |
void |
connect |
Connects the socket to a remote address for this socket. |
void |
connect |
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 DatagramChannel 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. |
<T> T |
getOption |
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 DatagramSocket , that is the buffer size, in bytes, used by the platform for input on this DatagramSocket . |
SocketAddress |
getRemoteSocketAddress() |
Returns the address of the endpoint this socket is connected to, or null 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, in bytes, used by the platform for output on this DatagramSocket . |
int |
getSoTimeout() |
Retrieve setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity). |
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 |
joinGroup |
Joins a multicast group. |
void |
leaveGroup |
Leave a multicast group on a specified local interface. |
void |
receive |
Receives a datagram packet from this socket. |
void |
send |
Sends a datagram packet from this socket. |
void |
setBroadcast |
Enable/disable SO_BROADCAST. |
static void |
setDatagramSocketImplFactory |
Deprecated. |
<T> DatagramSocket |
setOption |
Sets the value of a socket option. |
void |
setReceiveBufferSize |
Sets the SO_RCVBUF option to the specified value for this DatagramSocket . |
void |
setReuseAddress |
Enable/disable the SO_REUSEADDR socket option. |
void |
setSendBufferSize |
Sets the SO_SNDBUF option to the specified value for this DatagramSocket . |
void |
setSoTimeout |
Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. |
void |
setTrafficClass |
Sets traffic class or type-of-service octet in the IP datagram header for datagrams sent from this DatagramSocket. |
Set |
supportedOptions() |
Returns a set of the socket options supported by this socket. |
public DatagramSocket() throws SocketException
wildcard
address. 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 be bound.SecurityException
- if a security manager exists and its checkListen
method doesn't allow the operation.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 the address is null
an unbound socket will be created.
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.IllegalArgumentException
- if bindaddr is a SocketAddress subclass not supported by this socket.public DatagramSocket(int port) throws SocketException
wildcard
address. 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 use in the bind operation.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.IllegalArgumentException
- if port is out of range.
public DatagramSocket(int port, InetAddress laddr) throws SocketException
The local port must be between 0 and 65535 inclusive. A port number of zero
will let the system pick up an ephemeral port in a bind
operation.
If the IP address is a wildcard
address, or is null
, the socket will be bound to the wildcard address.
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 use in the bind operation.laddr
- local address to bind (can be null
)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.IllegalArgumentException
- if port is out of range.
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 this socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if invoking the bind
method with a parameter of null
. 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.
Care should be taken to ensure that a connected datagram socket is not shared with untrusted code. 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. Datagrams in the socket's socket receive buffer, which have not been received before invoking this method, may be discarded.
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 addressUncheckedIOException
- may be thrown if connect fails, for example, if the destination address is non-routablepublic void connect(SocketAddress addr) throws SocketException
If given an InetSocketAddress
, this method behaves as if invoking connect(InetAddress,int)
with the given socket addresses IP address and port number, except that the SocketException
that may be raised is not wrapped in an UncheckedIOException
. Datagrams in the socket's socket receive buffer, which have not been received before invoking this method, may be discarded.
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()
UncheckedIOException
- may be thrown if disconnect fails to dissolve the association and restore the socket to a consistent state.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.public SocketAddress getLocalSocketAddress()
SocketAddress
representing the local endpoint of this socket, or null
if it is closed or not bound yet.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, or if the socket is not connected and the packet address is not set or if its port is out of range.
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. 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. This method is interruptible in the following circumstances:
DatagramChannel
. In that case, interrupting a thread receiving a datagram packet will close the underlying channel and cause this method to throw ClosedByInterruptException
with the interrupt status set. SocketException
with the interrupt status set. If there is a security manager, and the socket is not currently connected to a remote address, a packet cannot be received if the security manager's checkAccept
method does not allow it. Datagrams that are not permitted by the security manager are silently discarded.
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.public 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 operationpublic int getLocalPort()
-1
if the socket is closed, or 0
if it is not bound yet.public void setSoTimeout(int timeout) throws SocketException
timeout
- the specified timeout in milliseconds.SocketException
- if there is an error in the underlying protocol, such as an UDP error.IllegalArgumentException
- if timeout
is negativepublic int getSoTimeout() throws SocketException
SocketException
- if there is an error in the underlying protocol, such as an UDP error.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 > 0
, this method is equivalent to calling setOption(StandardSocketOptions.SO_SNDBUF, size)
.size
- the size to which to set the send buffer size, in bytes. 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.public int getSendBufferSize() throws SocketException
DatagramSocket
, that is the buffer size, in bytes, used by the platform for output on this DatagramSocket
.getOption(StandardSocketOptions.SO_SNDBUF)
.DatagramSocket
SocketException
- if there is an error in the underlying protocol, such as an UDP error.public void setReceiveBufferSize(int size) throws SocketException
DatagramSocket
. The SO_RCVBUF option is used by the network implementation as a hint to size the underlying network I/O buffers. The SO_RCVBUF setting may also be used by the network implementation to determine the maximum size of the packet that can be received on this socket. Because SO_RCVBUF is a hint, applications that want to verify what size the buffers were set to should call getReceiveBufferSize()
.
Increasing SO_RCVBUF may allow the network implementation to buffer multiple packets when packets arrive faster than are being received using receive(DatagramPacket)
.
Note: It is implementation specific if a packet larger than SO_RCVBUF can be received.
size > 0
, this method is equivalent to calling setOption(StandardSocketOptions.SO_RCVBUF, size)
.size
- the size to which to set the receive buffer size, in bytes. 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.public int getReceiveBufferSize() throws SocketException
DatagramSocket
, that is the buffer size, in bytes, used by the platform for input on this DatagramSocket
.getOption(StandardSocketOptions.SO_RCVBUF)
.DatagramSocket
SocketException
- if there is an error in the underlying protocol, such as an UDP error.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.
setOption(StandardSocketOptions.SO_REUSEADDR, on)
.on
- whether to enable or disable theSocketException
- if an error occurs enabling or disabling the SO_REUSEADDR
socket option, or the socket is closed.public boolean getReuseAddress() throws SocketException
getOption(StandardSocketOptions.SO_REUSEADDR)
.boolean
indicating whether or not SO_REUSEADDR is enabled.SocketException
- if there is an error in the underlying protocol, such as an UDP error.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.
setOption(StandardSocketOptions.SO_BROADCAST, on)
.on
- whether or not to have broadcast turned on.SocketException
- if there is an error in the underlying protocol, such as an UDP error.public boolean getBroadcast() throws SocketException
getOption(StandardSocketOptions.SO_BROADCAST)
.boolean
indicating whether or not SO_BROADCAST is enabled.SocketException
- if there is an error in the underlying protocol, such as an UDP error.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.
setOption(StandardSocketOptions.IP_TOS, tc)
.tc
- an int
value for the bitset.SocketException
- if there is an error setting the traffic class or type-of-servicepublic 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.
getOption(StandardSocketOptions.IP_TOS)
.SocketException
- if there is an error obtaining the traffic class or type-of-service value.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 AutoCloseable
close
in interface Closeable
public 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 channel@Deprecated(since="17") public static void setDatagramSocketImplFactory(DatagramSocketImplFactory fac) throws IOException
DatagramChannel
, or subclass DatagramSocket
directly. DatagramSocket
. It has been mostly obsolete since Java 1.4. If required, a DatagramSocket
can be created to use a custom implementation by extending DatagramSocket
and using the protected constructor that takes an implementation as a parameter. 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.public <T> DatagramSocket setOption(SocketOption<T> name, T value) throws IOException
T
- The type of the socket option valuename
- The socket optionvalue
- The value of the socket option. A value of null
may be valid for some options.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
public <T> T getOption(SocketOption<T> name) throws IOException
T
- The type of the socket option valuename
- The socket optionUnsupportedOperationException
- 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.public Set<SocketOption<?>> supportedOptions()
public void joinGroup(SocketAddress mcastaddr, NetworkInterface netIf) throws IOException
In order to join a multicast group, the caller should specify the IP address of the multicast group to join, and the local network interface to receive multicast packets from.
mcastaddr
argument indicates the IP address of the multicast group to join. For historical reasons this is specified as a SocketAddress
. The default implementation only supports InetSocketAddress
and the port
information is ignored. netIf
argument specifies the local interface to receive multicast datagram packets, or null
to defer to the interface set for outgoing multicast datagrams. If null
, and no interface has been set, the behaviour is unspecified: any interface may be selected or the operation may fail with a SocketException
. It is possible to call this method several times to join several different multicast groups, or join the same group in several different networks. However, if the socket is already a member of the group, an IOException
will be thrown.
If there is a security manager, this method first calls its checkMulticast
method with the mcastaddr
argument as its argument.
setOption(SocketOption, Object)
with StandardSocketOptions.IP_MULTICAST_IF
.mcastaddr
- indicates the multicast address to join.netIf
- specifies the local interface to receive multicast datagram packets, or null
.IOException
- if there is an error joining, or when the address is not a multicast address, or the platform does not support multicastingSecurityException
- if a security manager exists and its checkMulticast
method doesn't allow the join.IllegalArgumentException
- if mcastaddr is null
or is a SocketAddress subclass not supported by this socketpublic void leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf) throws IOException
If there is a security manager, this method first calls its checkMulticast
method with the mcastaddr
argument as its argument.
mcastaddr
and netIf
arguments should identify a multicast group that was previously joined by this DatagramSocket
. It is possible to call this method several times to leave multiple different multicast groups previously joined, or leave the same group previously joined in multiple different networks. However, if the socket is not a member of the specified group in the specified network, an IOException
will be thrown.
mcastaddr
- is the multicast address to leave. This should contain the same IP address than that used for joining the group.netIf
- specifies the local interface or null
to defer to the interface set for outgoing multicast datagrams. If null
, and no interface has been set, the behaviour is unspecified: any interface may be selected or the operation may fail with a SocketException
.IOException
- if there is an error leaving or when the address is not a multicast address.SecurityException
- if a security manager exists and its checkMulticast
method doesn't allow the operation.IllegalArgumentException
- if mcastaddr is null
or is a SocketAddress subclass not supported by this socket.
© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/net/DatagramSocket.html
DatagramChannel
, or subclassDatagramSocket
directly.