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| java.lang.Object
 java.net.DatagramSocket
java.net.MulticastSocket
| MulticastSocket | | public class MulticastSocket extends DatagramSocket (Code) | | 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.
author:
Pavani Diwanji
since:
JDK1.1 |
| Constructor Summary | |
| public | MulticastSocket()
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. | | public | MulticastSocket(int port)
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. | | public | MulticastSocket(SocketAddress bindaddr)
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. |
| Method Summary | |
| public InetAddress | getInterface()
Retrieve the address of the network interface used for
multicast packets. | | public boolean | getLoopbackMode()
Get the setting for local loopback of multicast datagrams. | | public NetworkInterface | getNetworkInterface()
Get the multicast network interface set.
exception:
SocketException - if there is an error in the underlying protocol, such as a TCP error. | | public int | getTimeToLive()
Get the default time-to-live for multicast packets sent out on
the socket. | | public void | joinGroup(InetAddress mcastaddr)
Joins a multicast group. | | public void | joinGroup(SocketAddress mcastaddr, NetworkInterface netIf)
Joins the specified multicast group at the specified interface. | | public void | leaveGroup(InetAddress mcastaddr)
Leave a multicast group. | | public void | leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf)
Leave a multicast group on a specified local interface. | | public void | send(DatagramPacket p, byte ttl)
Sends a datagram packet to the destination, with a TTL (time-
to-live) other than the default for the socket. | | public void | setInterface(InetAddress inf)
Set the multicast network interface used by methods
whose behavior would be affected by the value of the
network interface. | | public 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. | | public void | setNetworkInterface(NetworkInterface netIf)
Specify the network interface for outgoing multicast datagrams
sent on this socket.
Parameters:
netIf - the interface
exception:
SocketException - if there is an error in the underlying protocol, such as a TCP error. | | public 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. |
| MulticastSocket | | public MulticastSocket() throws IOException(Code) | | 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
DatagramSocket#setReuseAddress(true) method is
called to enable the SO_REUSEADDR socket option.
exception:
IOException - if an I/O exception occurswhile creating the MulticastSocket
exception:
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
See Also: SecurityManager.checkListen
See Also: java.net.DatagramSocket.setReuseAddress(boolean)
See Also: |
| MulticastSocket | | public MulticastSocket(int port) throws IOException(Code) | | 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
DatagramSocket#setReuseAddress(true) method is
called to enable the SO_REUSEADDR socket option.
Parameters:
port - port to use
exception:
IOException - if an I/O exception occurswhile creating the MulticastSocket
exception:
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
See Also: SecurityManager.checkListen
See Also: java.net.DatagramSocket.setReuseAddress(boolean)
See Also: |
| MulticastSocket | | public MulticastSocket(SocketAddress bindaddr) throws IOException(Code) | | 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
DatagramSocket#setReuseAddress(true) method is
called to enable the SO_REUSEADDR socket option.
Parameters:
bindaddr - Socket address to bind to, or null foran unbound socket.
exception:
IOException - if an I/O exception occurswhile creating the MulticastSocket
exception:
SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.
See Also: SecurityManager.checkListen
See Also: java.net.DatagramSocket.setReuseAddress(boolean)
See Also:
since:
1.4 |
| getTimeToLive | | public int getTimeToLive() throws IOException(Code) | | Get the default time-to-live for multicast packets sent out on
the socket.
exception:
IOException - if an I/O exception occurs whilegetting the default time-to-live value the default time-to-live value
See Also: MulticastSocket.setTimeToLive(int) |
| joinGroup | | public void joinGroup(InetAddress mcastaddr) throws IOException(Code) | | 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.
Parameters:
mcastaddr - is the multicast address to join
exception:
IOException - if there is an error joiningor when the address is not a multicast address.
exception:
SecurityException - if a security manager exists and its checkMulticast method doesn't allow the join.
See Also: SecurityManager.checkMulticast(InetAddress) |
| leaveGroup | | public void leaveGroup(InetAddress mcastaddr) throws IOException(Code) | | 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.
Parameters:
mcastaddr - is the multicast address to leave
exception:
IOException - if there is an error leavingor when the address is not a multicast address.
exception:
SecurityException - if a security manager exists and its checkMulticast method doesn't allow the operation.
See Also: SecurityManager.checkMulticast(InetAddress) |
| send | | public void send(DatagramPacket p, byte ttl) throws IOException(Code) | | 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.
Parameters:
p - is the packet to be sent. The packet should containthe destination multicast ip address and the data to be sent.One does not need to be the member of the group to sendpackets to a destination multicast address.
Parameters:
ttl - optional time to live for multicast packet.default ttl is 1.
exception:
IOException - is raised if an error occurs i.eerror while setting ttl.
exception:
SecurityException - if a security manager exists and its checkMulticast or checkConnect method doesn't allow the send.
See Also: DatagramSocket.send
See Also: DatagramSocket.receive
See Also: SecurityManager.checkMulticast(java.net.InetAddressbyte)
See Also: SecurityManager.checkConnect |
| setInterface | | public void setInterface(InetAddress inf) throws SocketException(Code) | | Set the multicast network interface used by methods
whose behavior would be affected by the value of the
network interface. Useful for multihomed hosts.
Parameters:
inf - the InetAddress
exception:
SocketException - if there is an error in the underlying protocol, such as a TCP error.
See Also: MulticastSocket.getInterface() |
| setLoopbackMode | | public void setLoopbackMode(boolean disable) throws SocketException(Code) | | 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
MulticastSocket.getLoopbackMode()
Parameters:
disable - true to disable the LoopbackMode
throws:
SocketException - if an error occurs while setting the value
since:
1.4
See Also: MulticastSocket.getLoopbackMode |
| setTimeToLive | | public void setTimeToLive(int ttl) throws IOException(Code) | | 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.
exception:
IOException - if an I/O exception occurswhile setting the default time-to-live value
Parameters:
ttl - the time-to-live
See Also: MulticastSocket.getTimeToLive() |
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