java.lang.Object | ||
↳ | java.net.DatagramSocket | |
↳ | java.net.MulticastSocket |
The multicast datagram socket class is useful for sending and receiving IP multicast packets. A MulticastSocket is a (UDP) DatagramSocket, with additional capabilities for joining "groups" of other multicast hosts on the internet.
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.
Public Constructors | |||||||||||
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Create a multicast socket.
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Create a multicast socket and bind it to a specific port.
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Create a MulticastSocket bound to the specified socket address.
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Public Methods | |||||||||||
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Retrieve the address of the network interface used for
multicast packets.
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Get the setting for local loopback of multicast datagrams.
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Get the multicast network interface set.
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This method is deprecated.
use the getTimeToLive method instead, which returns
an int instead of a byte.
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Get the default time-to-live for multicast packets sent out on
the socket.
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Joins the specified multicast group at the specified interface.
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Joins a multicast group.
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Leave a multicast group on a specified local interface.
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Leave a multicast group.
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This method is deprecated.
Use the following code or its equivalent instead:
......
int ttl = mcastSocket.getTimeToLive();
mcastSocket.setTimeToLive(newttl);
mcastSocket.send(p);
mcastSocket.setTimeToLive(ttl);
......
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Set the multicast network interface used by methods
whose behavior would be affected by the value of the
network interface.
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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.
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Specify the network interface for outgoing multicast datagrams
sent on this socket.
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This method is deprecated.
use the setTimeToLive method instead, which uses
int instead of byte as the type for ttl.
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Set the default time-to-live for multicast packets sent out
on this
MulticastSocket in order to control the
scope of the multicasts. |
[Expand]
Inherited Methods | |||||||||||
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From class
java.net.DatagramSocket
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From class
java.lang.Object
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Create a multicast socket.
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
setReuseAddress(boolean)
method is
called to enable the SO_REUSEADDR socket option.
IOException | if an I/O exception occurs while creating the MulticastSocket |
---|---|
SecurityException | if a security manager exists and its
checkListen method doesn't allow the operation. |
Create a multicast socket and bind it to a specific port.
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
setReuseAddress(boolean)
method is
called to enable the SO_REUSEADDR socket option.
port | port to use |
---|
IOException | if an I/O exception occurs while creating the MulticastSocket |
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SecurityException | if a security manager exists and its
checkListen method doesn't allow the operation. |
Create a MulticastSocket bound to the specified socket address.
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
setReuseAddress(boolean)
method is
called to enable the SO_REUSEADDR socket option.
bindaddr | Socket address to bind to, or null for
an unbound socket. |
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IOException | if an I/O exception occurs while creating the MulticastSocket |
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SecurityException | if a security manager exists and its
checkListen method doesn't allow the operation. |
Retrieve the address of the network interface used for multicast packets.
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. |
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Get the setting for local loopback of multicast datagrams.
SocketException | if an error occurs while getting the value |
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Get the multicast network interface set.
NetworkInterface
currently setSocketException | if there is an error in the underlying protocol, such as a TCP error. |
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This method is deprecated.
use the getTimeToLive method instead, which returns
an int instead of a byte.
Get the default time-to-live for multicast packets sent out on the socket.
IOException | if an I/O exception occurs while getting the default time-to-live value |
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Get the default time-to-live for multicast packets sent out on the socket.
IOException | if an I/O exception occurs while getting the default time-to-live value |
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Joins the specified multicast group at the specified interface.
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 join |
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netIf | 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. |
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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 socket |
Joins a multicast group. Its behavior may be affected by
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 join |
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IOException | if there is an error joining or when the address is not a multicast address. |
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SecurityException | if a security manager exists and its
checkMulticast method doesn't allow the join. |
Leave a multicast group on a specified local interface.
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 leave |
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netIf | 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. |
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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 |
Leave a multicast group. Its behavior may be affected by
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 leave |
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IOException | if there is an error leaving or when the address is not a multicast address. |
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SecurityException | if a security manager exists and its
checkMulticast method doesn't allow the operation. |
This method is deprecated.
Use the following code or its equivalent instead:
......
int ttl = mcastSocket.getTimeToLive();
mcastSocket.setTimeToLive(newttl);
mcastSocket.send(p);
mcastSocket.setTimeToLive(ttl);
......
Sends a datagram packet to the destination, with a TTL (time-
to-live) other than the default for the socket. This method
need only be used in instances where a particular TTL is desired;
otherwise it is preferable to set a TTL once on the socket, and
use that default TTL for all packets. This method does not
alter the default TTL for the socket. Its behavior may be
affected by 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. |
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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. |
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SecurityException | if a security manager exists and its
checkMulticast or checkConnect
method doesn't allow the send. |
Set the multicast network interface used by methods whose behavior would be affected by the value of the network interface. Useful for multihomed hosts.
inf | the InetAddress |
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SocketException | if there is an error in the underlying protocol, such as a TCP error. |
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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.
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 LoopbackMode |
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SocketException | if an error occurs while setting the value |
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Specify the network interface for outgoing multicast datagrams sent on this socket.
netIf | the interface |
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SocketException | if there is an error in the underlying protocol, such as a TCP error. |
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This method is deprecated.
use the setTimeToLive method instead, which uses
int instead of byte as the type for ttl.
Set the default time-to-live for multicast packets sent out
on this 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-live |
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IOException | if an I/O exception occurs while setting the default time-to-live value |
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Set the default time-to-live for multicast packets sent out
on this 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.
ttl | the time-to-live |
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IOException | if an I/O exception occurs while setting the default time-to-live value |
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