java.net
Class MulticastANEPSocket

java.lang.Object
  |
  +--java.net.ANEPSocket
        |
        +--java.net.MulticastANEPSocket

public class MulticastANEPSocket

extends ANEPSocket

The multicast anep socket class is useful for sending and receiving IP multicast packets. A MulticastANEPSocket is an (ANDP) ANEPSocket, with additional capabilities for joining "groups" of other multicast hosts on the internet.

One would join a multicast group by first creating a MulticastANEPSocket with the desired type, then invoking the joinGroup(InetAddress groupAddr) method:

 // join a Multicast group and send the group salutations
 ...
 byte[] msg = {'H', 'e', 'l', 'l', 'o'};
 InetAddress group = InetAddress.getByName("228.5.6.7");
 MulticastANEPSocket s = new MulticastANEPSocket(6789);
 s.joinGroup(group);
 ANEPPacket hi = new ANEPPacket(6789, msg, 0, msg.length, group);
 s.send(hi);
 // get their responses!
 byte[] buf = new byte[1000];
 ANEPPacket recv = new ANEPPacket(buf, 0, 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 Summary

MulticastANEPSocket()
Create a multicast socket.

MulticastANEPSocket(int type)
Create a multicast socket and bind it to a specific type.

Method Summary

int	getHOPS()
int	getInterface() Retrieve the address of the network interface used for multicast packets.
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.Its behavior may be affected by setInterface.
void	leaveGroup(InetAddress mcastaddr) Leave a multicast group.
void	send(ANEPPacket p, byte ttl) Sends a ANEP packet to the destination, with a TTL (time- to-live) other than the default for the socket.
void	setHOPS(int ttl)
void	setInterface(InetAddress inf)
void	setInterface(int inf) Set the multicast network interface used by methods whose behavior would be affected by the value of the network interface.
void	setTimeToLive(int ttl) Set the default time-to-live for multicast packets sent out on this socket.
void	setTTL(byte ttl) Deprecated. use the setTimeToLive method instead, which uses int instead of byte as the type for ttl.

Methods inherited from class java.net.ANEPSocket

allowOptionTypes, bind, close, connect, disconnect, getFlowLabel, getInetAddress, getLocalAddress, getLocalType, getNetAuthenticate, getNetEncryption, getReceiveBufferSize, getSendBufferSize, getSoReuse, getSoTimeout, getTrafficClass, getTransportAuthenticate, getTransportEncryption, getType, receive, send, setANEPDiscard, setFlowLabel, setNetAuthenticate, setNetEncryption, setReceiveBufferSize, setSendBufferSize, setSoReuse, setSoTimeout, setTrafficClass, setTransportAuthenticate, setTransportEncryption

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MulticastANEPSocket

public MulticastANEPSocket()
                    throws java.io.IOException

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.

Throws:

java.lang.SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.

See Also:

SecurityManager.checkListen(int)

MulticastANEPSocket

public MulticastANEPSocket(int type)
                    throws java.io.IOException

Create a multicast socket and bind it to a specific type.

Parameters:

type - packet type

Method Detail

setTTL

public void setTTL(byte ttl)
            throws java.io.IOException

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 socket. The TTL sets the IP time-to-live for ANEPPackets sent to a MulticastGroup, which specifies how many "hops" that the packet will be forwarded on the network before it expires.

The ttl is an unsigned 8-bit quantity, and so must be in the range 0 <= ttl <= 0xFF .

Parameters:

ttl - the time-to-live

setTimeToLive

public void setTimeToLive(int ttl)
                   throws java.io.IOException

Set the default time-to-live for multicast packets sent out on this socket. The TTL sets the IP time-to-live for ANEPPackets sent to a MulticastGroup, which specifies how many "hops" that the packet will be forwarded on the network before it expires.

The ttl must be in the range 0 <= ttl <= 255 or an IllegalArgumentException will be thrown.

Parameters:

ttl - the time-to-live

setHOPS

public void setHOPS(int ttl)
             throws java.io.IOException

getTTL

public byte getTTL()
            throws java.io.IOException

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.

getTimeToLive

public int getTimeToLive()
                  throws java.io.IOException

Get the default time-to-live for multicast packets sent out on the socket.

getHOPS

public int getHOPS()
            throws java.io.IOException

joinGroup

public void joinGroup(InetAddress mcastaddr)
               throws java.io.IOException

Joins a multicast group.Its behavior may be affected by setInterface.

Parameters:

mcastaddr - is the multicast address to join

Throws:

java.io.IOException - if there is an error joining or when the address is not a multicast address.

leaveGroup

public void leaveGroup(InetAddress mcastaddr)
                throws java.io.IOException

Leave a multicast group. Its behavior may be affected by setInterface.

Parameters:

mcastaddr - is the multicast address to leave

Throws:

java.io.IOException - if there is an error leaving or when the address is not a multicast address.

setInterface

public void setInterface(int inf)
                  throws java.net.SocketException

Set the multicast network interface used by methods whose behavior would be affected by the value of the network interface. Useful for multihomed hosts.

setInterface

public void setInterface(InetAddress inf)
                  throws java.net.SocketException

getInterface

public int getInterface()
                 throws java.net.SocketException

Retrieve the address of the network interface used for multicast packets.

send

public void send(ANEPPacket p,
                 byte ttl)
          throws java.io.IOException

Sends a ANEP 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.

Parameters:

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.

Throws:

java.io.IOException - is raised if an error occurs i.e error while setting ttl.

See Also:

ANEPSocket.send(java.net.ANEPPacket), ANEPSocket.receive(java.net.ANEPPacket)