java.lang.Object | +--java.net.DatagramSocket | +--java.net.MulticastSocket
Untamed: 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.
MulticastSocket()
MulticastSocket(int port)
MulticastSocket(SocketAddress bindaddr)
InetAddress
getInterface()
int
getTimeToLive()
byte
getTTL()
void
joinGroup(SocketAddress mcastaddr,
NetworkInterface netIf)
void
leaveGroup(SocketAddress mcastaddr,
NetworkInterface netIf)
void
send(DatagramPacket p,
byte ttl)
void
setInterface(InetAddress inf)
void
setLoopbackMode(boolean disable)
void
setNetworkInterface(NetworkInterface netIf)
void
setTimeToLive(int ttl)
MulticastSocket in order to control the
scope of the multicasts.
void
setTTL(byte ttl)
bind, close, connect, connect, createImpl, disconnect, getBroadcast, getChannel, getImpl, getInetAddress, getLocalAddress, getLocalPort, getLocalSocketAddress, getPort, getReceiveBufferSize, getRemoteSocketAddress, getReuseAddress, getSendBufferSize, getSoTimeout, getTrafficClass, isBound, isClosed, isConnected, receive, send, setBroadcast, setDatagramSocketImplFactory, setReceiveBufferSize, setReuseAddress, setSendBufferSize, setSoTimeout, setTrafficClass
private Object ttlLock
private Object infLock
private InetAddress infAddress
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(true) method is
called to enable the SO_REUSEADDR socket option.
SecurityManager.checkListen(int),
java.net.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(true) method is
called to enable the SO_REUSEADDR socket option.
port - port to useSecurityManager.checkListen(int),
java.net.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(true) method is
called to enable the SO_REUSEADDR socket option.
bindaddr - Socket address to bind to, or null for
an unbound socket.SecurityManager.checkListen(int),
java.net.DatagramSocket#setReuseAddress(boolean)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-live
IOExceptiongetTTL()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.
ttl - the time-to-live
IOExceptiongetTimeToLive()public byte getTTL() throws IOException
IOExceptionsetTTL(byte)public int getTimeToLive() throws IOException
IOExceptionsetTimeToLive(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 join
IOExceptionSecurityManager.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 leave
IOExceptionSecurityManager.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)
IllegalArgumentException - if mcastaddr is null or is a
SocketAddress subclass not supported by this socket
IOExceptionSecurityManager.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)
IllegalArgumentException - if mcastaddr is null or is a
SocketAddress subclass not supported by this socket
IOExceptionSecurityManager.checkMulticast(InetAddress)public void setInterface(InetAddress inf) throws SocketException
inf - the InetAddress
SocketExceptiongetInterface()public InetAddress getInterface() throws SocketException
InetAddress representing
the address of the network interface used for
multicast packets.
SocketExceptionsetInterface(java.net.InetAddress)public void setNetworkInterface(NetworkInterface netIf) throws SocketException
netIf - the interface
SocketExceptiongetNetworkInterface()public NetworkInterface getNetworkInterface() throws SocketException
NetworkInterface currently set
SocketExceptionsetNetworkInterface(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 LoopbackMode
SocketException - if an error occurs while setting the valuegetLoopbackMode()public boolean getLoopbackMode() throws SocketException
SocketException - if an error occurs while getting the valuesetLoopbackMode(boolean)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.
IOExceptionDatagramSocket.send(java.net.DatagramPacket),
DatagramSocket.receive(java.net.DatagramPacket),
SecurityManager.checkMulticast(java.net.InetAddress, byte),
SecurityManager.checkConnect(java.lang.String, int)