- java.lang.Object
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- java.net.DatagramSocket
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- java.net.MulticastSocket
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- All Implemented Interfaces:
- Closeable, AutoCloseable
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
to239.255.255.255
, 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.
- Since:
- JDK1.1
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Constructor Summary
Constructors Constructor and Description MulticastSocket()
Create a multicast socket.MulticastSocket(int port)
Create a multicast socket and bind it to a specific port.MulticastSocket(SocketAddress bindaddr)
Create a MulticastSocket bound to the specified socket address.
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Method Summary
Methods Modifier and Type Method and Description InetAddress
getInterface()
Retrieve the address of the network interface used for multicast packets.boolean
getLoopbackMode()
Get the setting for local loopback of multicast datagrams.NetworkInterface
getNetworkInterface()
Get the multicast network interface set.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.void
joinGroup(SocketAddress mcastaddr, NetworkInterface netIf)
Joins the specified multicast group at the specified interface.void
leaveGroup(InetAddress mcastaddr)
Leave a multicast group.void
leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf)
Leave a multicast group on a specified local interface.void
send(DatagramPacket p, byte ttl)
Deprecated.Use the following code or its equivalent instead: ...... int ttl = mcastSocket.getTimeToLive(); mcastSocket.setTimeToLive(newttl); mcastSocket.send(p); mcastSocket.setTimeToLive(ttl); ......void
setInterface(InetAddress inf)
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
setNetworkInterface(NetworkInterface netIf)
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 thisMulticastSocket
in order to control the scope of the multicasts.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.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
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Constructor Detail
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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
DatagramSocket.setReuseAddress(boolean)
method is called to enable the SO_REUSEADDR socket option.- Throws:
IOException
- if an I/O exception occurs while creating the MulticastSocketSecurityException
- if a security manager exists and itscheckListen
method doesn't allow the operation.- See Also:
SecurityManager.checkListen(int)
,DatagramSocket.setReuseAddress(boolean)
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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 theport
argument as its argument to ensure the operation is allowed. This could result in a SecurityException.When the socket is created the
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 MulticastSocketSecurityException
- if a security manager exists and itscheckListen
method doesn't allow the operation.- See Also:
SecurityManager.checkListen(int)
,DatagramSocket.setReuseAddress(boolean)
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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
DatagramSocket.setReuseAddress(boolean)
method is called to enable the SO_REUSEADDR socket option.- Parameters:
bindaddr
- Socket address to bind to, ornull
for an unbound socket.- Throws:
IOException
- if an I/O exception occurs while creating the MulticastSocketSecurityException
- if a security manager exists and itscheckListen
method doesn't allow the operation.- Since:
- 1.4
- See Also:
SecurityManager.checkListen(int)
,DatagramSocket.setReuseAddress(boolean)
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Method Detail
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setTTL
@Deprecated public void setTTL(byte ttl) throws 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 thisMulticastSocket
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- See Also:
getTTL()
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setTimeToLive
public void setTimeToLive(int ttl) throws IOException
Set the default time-to-live for multicast packets sent out on thisMulticastSocket
in order to control the scope of the multicasts.The ttl must be in the range
0 <= ttl <= 255
or anIllegalArgumentException
will be thrown. Multicast packets sent with a TTL of0
are not transmitted on the network but may be delivered locally.- Parameters:
ttl
- the time-to-live- Throws:
IOException
- if an I/O exception occurs while setting the default time-to-live value- See Also:
getTimeToLive()
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getTTL
@Deprecated public byte getTTL() throws 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.- Returns:
- the default time-to-live value
- Throws:
IOException
- if an I/O exception occurs while getting the default time-to-live value- See Also:
setTTL(byte)
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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- See Also:
setTimeToLive(int)
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joinGroup
public void joinGroup(InetAddress mcastaddr) throws IOException
Joins a multicast group. Its behavior may be affected bysetInterface
orsetNetworkInterface
.If there is a security manager, this method first calls its
checkMulticast
method with themcastaddr
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.SecurityException
- if a security manager exists and itscheckMulticast
method doesn't allow the join.- See Also:
SecurityManager.checkMulticast(InetAddress)
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leaveGroup
public void leaveGroup(InetAddress mcastaddr) throws IOException
Leave a multicast group. Its behavior may be affected bysetInterface
orsetNetworkInterface
.If there is a security manager, this method first calls its
checkMulticast
method with themcastaddr
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.SecurityException
- if a security manager exists and itscheckMulticast
method doesn't allow the operation.- See Also:
SecurityManager.checkMulticast(InetAddress)
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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 themcastaddr
argument as its argument.- Parameters:
mcastaddr
- is the multicast address to joinnetIf
- specifies the local interface to receive multicast datagram packets, or null to defer to the interface set bysetInterface(InetAddress)
orsetNetworkInterface(NetworkInterface)
- Throws:
IOException
- if there is an error joining or when the address is not a multicast address.SecurityException
- if a security manager exists and itscheckMulticast
method doesn't allow the join.IllegalArgumentException
- if mcastaddr is null or is a SocketAddress subclass not supported by this socket- Since:
- 1.4
- See Also:
SecurityManager.checkMulticast(InetAddress)
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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 themcastaddr
argument as its argument.- Parameters:
mcastaddr
- is the multicast address to leavenetIf
- specifies the local interface or null to defer to the interface set bysetInterface(InetAddress)
orsetNetworkInterface(NetworkInterface)
- Throws:
IOException
- if there is an error leaving or when the address is not a multicast address.SecurityException
- if a security manager exists and itscheckMulticast
method doesn't allow the operation.IllegalArgumentException
- if mcastaddr is null or is a SocketAddress subclass not supported by this socket- Since:
- 1.4
- See Also:
SecurityManager.checkMulticast(InetAddress)
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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.- See Also:
getInterface()
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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.- See Also:
setInterface(java.net.InetAddress)
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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.- Since:
- 1.4
- See Also:
getNetworkInterface()
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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.- Since:
- 1.4
- See Also:
setNetworkInterface(NetworkInterface)
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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
getLoopbackMode()
- Parameters:
disable
-true
to disable the LoopbackMode- Throws:
SocketException
- if an error occurs while setting the value- Since:
- 1.4
- See Also:
getLoopbackMode()
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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- Since:
- 1.4
- See Also:
setLoopbackMode(boolean)
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send
@Deprecated public void send(DatagramPacket p, byte ttl) throws IOException
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 bysetInterface
.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'scheckMulticast
method withp.getAddress()
andttl
as its arguments. If the evaluation of that expression is false, this method instead calls the security manager'scheckConnect
method with argumentsp.getAddress().getHostAddress()
andp.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.SecurityException
- if a security manager exists and itscheckMulticast
orcheckConnect
method doesn't allow the send.- See Also:
DatagramSocket.send(java.net.DatagramPacket)
,DatagramSocket.receive(java.net.DatagramPacket)
,SecurityManager.checkMulticast(java.net.InetAddress, byte)
,SecurityManager.checkConnect(java.lang.String, int)
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Bij voorbaat dank.
Document heeft de 11/06/2005 gemaakt, de laatste keer de 04/03/2020 gewijzigd
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