This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.


java.net
class MulticastSocket

java.lang.Object extended by java.net.DatagramSocket extended by java.net.MulticastSocket

Most common way to construct:

MulticastSocket s = new MulticastSocket(6789);

Based on 123 examples


public class MulticastSocket
extends DatagramSocket

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.

See Also (auto-generated):

InetAddress

DatagramSocket

DatagramPacket


Constructor Summary

          Create a multicast socket.
MulticastSocket(int port)

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

          Create a MulticastSocket bound to the specified socket address.
 
Method Summary
 InetAddress

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

          Get the setting for local loopback of multicast datagrams.
 NetworkInterface

          Get the multicast network interface set.
 int

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

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

          Joins a multicast group.
 void

          Joins the specified multicast group at the specified interface.
 void

          Leave a multicast group.
 void

          Leave a multicast group on a specified local interface.
 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.
 void

          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

          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)

          Set the default time-to-live for multicast packets sent out on this MulticastSocket in order to control the scope of the multicasts.
 
Methods inherited from class java.net.DatagramSocket
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
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

MulticastSocket

public MulticastSocket()
                throws 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.

When the socket is created the {@link DatagramSocket#setReuseAddress(boolean)} method is called to enable the SO_REUSEADDR socket option.

Throws:
IOException - if an I/O exception occurs while creating the MulticastSocket

MulticastSocket

public MulticastSocket(int port)
                throws IOException
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 {@link DatagramSocket#setReuseAddress(boolean)} method is called to enable the SO_REUSEADDR socket option.

Parameters:
port - port to use
Throws:
IOException - if an I/O exception occurs while creating the MulticastSocket

MulticastSocket

public MulticastSocket(SocketAddress bindaddr)
                throws IOException
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 {@link DatagramSocket#setReuseAddress(boolean)} method is called to enable the SO_REUSEADDR socket option.

Parameters:
bindaddr - Socket address to bind to, or null for an unbound socket.
Throws:
IOException - if an I/O exception occurs while creating the MulticastSocket
Method Detail

getInterface

public InetAddress getInterface()
                         throws SocketException
Retrieve the address of the network interface used for multicast packets.

Returns:
An InetAddress representing the address of the network interface used for multicast packets.
Throws:
SocketException - if there is an error in the underlying protocol, such as a TCP error.

getLoopbackMode

public boolean getLoopbackMode()
                        throws SocketException
Get the setting for local loopback of multicast datagrams.

Returns:
true if the LoopbackMode has been disabled
Throws:
SocketException - if an error occurs while getting the value

getNetworkInterface

public NetworkInterface getNetworkInterface()
                                     throws SocketException
Get the multicast network interface set.

Returns:
the multicast NetworkInterface currently set
Throws:
SocketException - if there is an error in the underlying protocol, such as a TCP error.

getTimeToLive

public int getTimeToLive()
                  throws IOException
Get the default time-to-live for multicast packets sent out on the socket.

Returns:
the default time-to-live value
Throws:
IOException - if an I/O exception occurs while getting the default time-to-live value

getTTL

public byte getTTL()
            throws IOException
Get the default time-to-live for multicast packets sent out on the socket.

Returns:
the default time-to-live value
Throws:
IOException - if an I/O exception occurs while getting the default time-to-live value

joinGroup

public void joinGroup(InetAddress mcastaddr)
               throws IOException
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
Throws:
IOException - if there is an error joining or when the address is not a multicast address.

joinGroup

public void joinGroup(SocketAddress mcastaddr,
                      NetworkInterface netIf)
               throws IOException
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.

Parameters:
mcastaddr - is the multicast address to join
netIf - specifies the local interface to receive multicast datagram packets, or null to defer to the interface set by {@link MulticastSocket#setInterface(InetAddress)} or {@link MulticastSocket#setNetworkInterface(NetworkInterface)}
Throws:
IOException - if there is an error joining or when the address is not a multicast address.

leaveGroup

public void leaveGroup(InetAddress mcastaddr)
                throws IOException
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
Throws:
IOException - if there is an error leaving or when the address is not a multicast address.

leaveGroup

public void leaveGroup(SocketAddress mcastaddr,
                       NetworkInterface netIf)
                throws IOException
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.

Parameters:
mcastaddr - is the multicast address to leave
netIf - specifies the local interface or null to defer to the interface set by {@link MulticastSocket#setInterface(InetAddress)} or {@link MulticastSocket#setNetworkInterface(NetworkInterface)}
Throws:
IOException - if there is an error leaving or when the address is not a multicast address.

send

public void send(DatagramPacket p,
                 byte ttl)
          throws IOException
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 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:
IOException - is raised if an error occurs i.e error while setting ttl.

setInterface

public void setInterface(InetAddress inf)
                  throws 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.

Parameters:
inf - the InetAddress
Throws:
SocketException - if there is an error in the underlying protocol, such as a TCP error.

setLoopbackMode

public void setLoopbackMode(boolean disable)
                     throws SocketException
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 {@link #getLoopbackMode()}

Parameters:
disable - true to disable the LoopbackMode
Throws:
SocketException - if an error occurs while setting the value

setNetworkInterface

public void setNetworkInterface(NetworkInterface netIf)
                         throws SocketException
Specify the network interface for outgoing multicast datagrams sent on this socket.

Parameters:
netIf - the interface
Throws:
SocketException - if there is an error in the underlying protocol, such as a TCP error.

setTimeToLive

public void setTimeToLive(int ttl)
                   throws IOException
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.

Parameters:
ttl - the time-to-live
Throws:
IOException - if an I/O exception occurs while setting the default time-to-live value

setTTL

public void setTTL(byte ttl)
            throws IOException
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 .

Parameters:
ttl - the time-to-live
Throws:
IOException - if an I/O exception occurs while setting the default time-to-live value


This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
This page displays the Jadeite version of the documention, which is derived from the offical documentation that contains this copyright notice:
Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.