public class MulticastSocket extends DatagramSocket
A multicast group is specified by a class D IP address
and by a standard UDP port number. Class D IP addresses
are in the range 224.0.0.0
to 239.255.255.255
,
inclusive. The address 224.0.0.0 is reserved and should not be used.
One would join a multicast group by first creating a MulticastSocket
with the desired port, then invoking the
joinGroup(InetAddress groupAddr)
method:
// join a Multicast group and send the group salutations ... String msg = "Hello"; InetAddress group = InetAddress.getByName("228.5.6.7"); MulticastSocket s = new MulticastSocket(6789); s.joinGroup(group); DatagramPacket hi = new DatagramPacket(msg.getBytes(), msg.length(), group, 6789); s.send(hi); // get their responses! byte[] buf = new byte[1000]; DatagramPacket recv = new DatagramPacket(buf, buf.length); s.receive(recv); ... // OK, I'm done talking - leave the group... s.leaveGroup(group);When one sends a message to a multicast group, all subscribing recipients to that host and port receive the message (within the time-to-live range of the packet, see below). The socket needn't be a member of the multicast group to send messages to it.
When a socket subscribes to a multicast group/port, it receives datagrams sent by other hosts to the group/port, as do all other members of the group and port. A socket relinquishes membership in a group by the leaveGroup(InetAddress addr) method. Multiple MulticastSocket's may subscribe to a multicast group and port concurrently, and they will all receive group datagrams.
Currently applets are not allowed to use multicast sockets.
Constructor and Description |
---|
MulticastSocket()
Create a multicast socket.
|
MulticastSocket(int port)
Create a multicast socket and bind it to a specific port.
|
MulticastSocket(SocketAddress bindaddr)
Create a MulticastSocket bound to the specified socket address.
|
Modifier and Type | Method and Description |
---|---|
InetAddress |
getInterface()
Retrieve the address of the network interface used for
multicast packets.
|
boolean |
getLoopbackMode()
Get the setting for local loopback of multicast datagrams.
|
NetworkInterface |
getNetworkInterface()
Get the multicast network interface set.
|
int |
getTimeToLive()
Get the default time-to-live for multicast packets sent out on
the socket.
|
byte |
getTTL()
Deprecated.
use the getTimeToLive method instead, which returns
an int instead of a byte.
|
void |
joinGroup(InetAddress mcastaddr)
Joins a multicast group.
|
void |
joinGroup(SocketAddress mcastaddr,
NetworkInterface netIf)
Joins the specified multicast group at the specified interface.
|
void |
leaveGroup(InetAddress mcastaddr)
Leave a multicast group.
|
void |
leaveGroup(SocketAddress mcastaddr,
NetworkInterface netIf)
Leave a multicast group on a specified local interface.
|
void |
send(DatagramPacket p,
byte ttl)
Deprecated.
Use the following code or its equivalent instead:
......
int ttl = mcastSocket.getTimeToLive();
mcastSocket.setTimeToLive(newttl);
mcastSocket.send(p);
mcastSocket.setTimeToLive(ttl);
......
|
void |
setInterface(InetAddress inf)
Set the multicast network interface used by methods
whose behavior would be affected by the value of the
network interface.
|
void |
setLoopbackMode(boolean disable)
Disable/Enable local loopback of multicast datagrams
The option is used by the platform's networking code as a hint
for setting whether multicast data will be looped back to
the local socket.
|
void |
setNetworkInterface(NetworkInterface netIf)
Specify the network interface for outgoing multicast datagrams
sent on this socket.
|
void |
setTimeToLive(int ttl)
Set the default time-to-live for multicast packets sent out
on this
MulticastSocket in order to control the
scope of the multicasts. |
void |
setTTL(byte ttl)
Deprecated.
use the setTimeToLive method instead, which uses
int instead of byte as the type for ttl.
|
bind, close, connect, connect, disconnect, getBroadcast, getChannel, getInetAddress, getLocalAddress, getLocalPort, getLocalSocketAddress, getPort, getReceiveBufferSize, getRemoteSocketAddress, getReuseAddress, getSendBufferSize, getSoTimeout, getTrafficClass, isBound, isClosed, isConnected, receive, send, setBroadcast, setDatagramSocketImplFactory, setReceiveBufferSize, setReuseAddress, setSendBufferSize, setSoTimeout, setTrafficClass
public MulticastSocket() throws IOException
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.
When the socket is created the
DatagramSocket.setReuseAddress(boolean)
method is
called to enable the SO_REUSEADDR socket option.
IOException
- if an I/O exception occurs
while creating the MulticastSocketSecurityException
- if a security manager exists and its
checkListen
method doesn't allow the operation.SecurityManager.checkListen(int)
,
DatagramSocket.setReuseAddress(boolean)
public MulticastSocket(int port) throws IOException
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.
When the socket is created the
DatagramSocket.setReuseAddress(boolean)
method is
called to enable the SO_REUSEADDR socket option.
port
- port to useIOException
- if an I/O exception occurs
while creating the MulticastSocketSecurityException
- if a security manager exists and its
checkListen
method doesn't allow the operation.SecurityManager.checkListen(int)
,
DatagramSocket.setReuseAddress(boolean)
public MulticastSocket(SocketAddress bindaddr) throws IOException
Or, if the address is null
, create an unbound socket.
If there is a security manager,
its checkListen
method is first called
with the SocketAddress port as its argument to ensure the operation is allowed.
This could result in a SecurityException.
When the socket is created the
DatagramSocket.setReuseAddress(boolean)
method is
called to enable the SO_REUSEADDR socket option.
bindaddr
- Socket address to bind to, or null
for
an unbound socket.IOException
- if an I/O exception occurs
while creating the MulticastSocketSecurityException
- if a security manager exists and its
checkListen
method doesn't allow the operation.SecurityManager.checkListen(int)
,
DatagramSocket.setReuseAddress(boolean)
@Deprecated public void setTTL(byte ttl) throws IOException
MulticastSocket
in order to control the
scope of the multicasts.
The ttl is an unsigned 8-bit quantity, and so must be
in the range 0 <= ttl <= 0xFF
.
ttl
- the time-to-liveIOException
- if an I/O exception occurs
while setting the default time-to-live valuegetTTL()
public void setTimeToLive(int ttl) throws IOException
MulticastSocket
in order to control the
scope of the multicasts.
The ttl must be in the range 0 <= ttl <=
255
or an IllegalArgumentException
will be thrown.
Multicast packets sent with a TTL of 0
are not transmitted
on the network but may be delivered locally.
ttl
- the time-to-liveIOException
- if an I/O exception occurs while setting the
default time-to-live valuegetTimeToLive()
@Deprecated public byte getTTL() throws IOException
IOException
- if an I/O exception occurs
while getting the default time-to-live valuesetTTL(byte)
public int getTimeToLive() throws IOException
IOException
- if an I/O exception occurs while
getting the default time-to-live valuesetTimeToLive(int)
public void joinGroup(InetAddress mcastaddr) throws IOException
setInterface
or setNetworkInterface
.
If there is a security manager, this method first
calls its checkMulticast
method
with the mcastaddr
argument
as its argument.
mcastaddr
- is the multicast address to joinIOException
- if there is an error joining
or when the address is not a multicast address.SecurityException
- if a security manager exists and its
checkMulticast
method doesn't allow the join.SecurityManager.checkMulticast(InetAddress)
public void leaveGroup(InetAddress mcastaddr) throws IOException
setInterface
or setNetworkInterface
.
If there is a security manager, this method first
calls its checkMulticast
method
with the mcastaddr
argument
as its argument.
mcastaddr
- is the multicast address to leaveIOException
- 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.SecurityManager.checkMulticast(InetAddress)
public void joinGroup(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
- is the multicast address to joinnetIf
- specifies the local interface to receive multicast
datagram packets, or null to defer to the interface set by
setInterface(InetAddress)
or
setNetworkInterface(NetworkInterface)
IOException
- if there is an error joining
or when the address is not a multicast address.SecurityException
- 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 socketSecurityManager.checkMulticast(InetAddress)
public 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
- is the multicast address to leavenetIf
- specifies the local interface or null to defer
to the interface set by
setInterface(InetAddress)
or
setNetworkInterface(NetworkInterface)
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 socketSecurityManager.checkMulticast(InetAddress)
public void setInterface(InetAddress inf) throws SocketException
inf
- the InetAddressSocketException
- if there is an error in
the underlying protocol, such as a TCP error.getInterface()
public InetAddress getInterface() throws SocketException
InetAddress
representing
the address of the network interface used for
multicast packets.SocketException
- if there is an error in
the underlying protocol, such as a TCP error.setInterface(java.net.InetAddress)
public void setNetworkInterface(NetworkInterface netIf) throws SocketException
netIf
- the interfaceSocketException
- if there is an error in
the underlying protocol, such as a TCP error.getNetworkInterface()
public NetworkInterface getNetworkInterface() throws SocketException
NetworkInterface
currently setSocketException
- if there is an error in
the underlying protocol, such as a TCP error.setNetworkInterface(NetworkInterface)
public void setLoopbackMode(boolean disable) throws SocketException
Because this option is a hint, applications that want to
verify what loopback mode is set to should call
getLoopbackMode()
disable
- true
to disable the LoopbackModeSocketException
- if an error occurs while setting the valuegetLoopbackMode()
public boolean getLoopbackMode() throws SocketException
SocketException
- if an error occurs while getting the valuesetLoopbackMode(boolean)
@Deprecated public void send(DatagramPacket p, byte ttl) throws IOException
setInterface
.
If there is a security manager, 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()
and ttl
as its arguments.
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
- is the packet to be sent. The packet should contain
the destination multicast ip address and the data to be sent.
One does not need to be the member of the group to send
packets to a destination multicast address.ttl
- optional time to live for multicast packet.
default ttl is 1.IOException
- is raised if an error occurs i.e
error while setting ttl.SecurityException
- if a security manager exists and its
checkMulticast
or checkConnect
method doesn't allow the send.DatagramSocket.send(java.net.DatagramPacket)
,
DatagramSocket.receive(java.net.DatagramPacket)
,
SecurityManager.checkMulticast(java.net.InetAddress, byte)
,
SecurityManager.checkConnect(java.lang.String, int)
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