MulticastSocket

open class MulticastSocket : DatagramSocket
kotlin.Any
   ↳ java.net.DatagramSocket
   ↳ java.net.MulticastSocket

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.

Summary

Public constructors

Create a multicast socket.

<init>(port: Int)

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

<init>(bindaddr: SocketAddress!)

Create a MulticastSocket bound to the specified socket address.

Public methods
open Unit

Set the default time-to-live for multicast packets sent out on this MulticastSocket in order to control the scope of the multicasts.

open Unit
setTTL(ttl: Byte)

Set the default time-to-live for multicast packets sent out on this MulticastSocket in order to control the scope of the multicasts.

open Byte

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

open Unit

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.

open Unit

Specify the network interface for outgoing multicast datagrams sent on this socket.

open Unit
leaveGroup(mcastaddr: InetAddress!)

Leave a multicast group.

open Unit
leaveGroup(mcastaddr: SocketAddress!, netIf: NetworkInterface!)

Leave a multicast group on a specified local interface.

open InetAddress!

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

open Unit
joinGroup(mcastaddr: InetAddress!)

Joins a multicast group.

open Unit
joinGroup(mcastaddr: SocketAddress!, netIf: NetworkInterface!)

Joins the specified multicast group at the specified interface.

open Int

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

open NetworkInterface!

Get the multicast network interface set.

open Boolean

Get the setting for local loopback of multicast datagrams.

open Unit

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

open Unit
send(p: DatagramPacket!, ttl: Byte)

Sends a datagram packet to the destination, with a TTL (time- to-live) other than the default for the socket.

Inherited functions

Public constructors

<init>

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. 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.

Exceptions
IOException if an I/O exception occurs while creating the MulticastSocket
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.

<init>

MulticastSocket(port: Int)

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(boolean) method is called to enable the SO_REUSEADDR socket option.

Parameters
port Int: port to use
Exceptions
IOException if an I/O exception occurs while creating the MulticastSocket
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.

<init>

added in API level 1.4
MulticastSocket(bindaddr: SocketAddress!)

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 SocketAddress!: Socket address to bind to, or null for an unbound socket.
Exceptions
IOException if an I/O exception occurs while creating the MulticastSocket
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.

Public methods

setTimeToLive

open fun setTimeToLive(ttl: Int): Unit

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. Multicast packets sent with a TTL of 0 are not transmitted on the network but may be delivered locally.

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

See Also

setTTL

open fun setTTL(ttl: Byte): Unit

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 Byte: the time-to-live
Exceptions
IOException if an I/O exception occurs while setting the default time-to-live value

See Also

getTTL

open fun getTTL(): Byte

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

Return
Byte: the default time-to-live value
Exceptions
IOException if an I/O exception occurs while getting the default time-to-live value

See Also

setLoopbackMode

added in API level 1.4
open fun setLoopbackMode(disable: Boolean): Unit

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 Boolean: true to disable the LoopbackMode
Exceptions
SocketException if an error occurs while setting the value

See Also

setNetworkInterface

added in API level 1.4
open fun setNetworkInterface(netIf: NetworkInterface!): Unit

Specify the network interface for outgoing multicast datagrams sent on this socket.

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

leaveGroup

open fun leaveGroup(mcastaddr: InetAddress!): Unit

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 InetAddress!: is the multicast address to leave
Exceptions
IOException if there is an error leaving or when the address is not a multicast address.
SecurityException if a security manager exists and its checkMulticast method doesn't allow the operation.

leaveGroup

added in API level 1.4
open fun leaveGroup(mcastaddr: SocketAddress!, netIf: NetworkInterface!): Unit

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 SocketAddress!: is the multicast address to leave
netIf SocketAddress!: specifies the local interface or null to defer to the interface set by MulticastSocket#setInterface(InetAddress) or MulticastSocket#setNetworkInterface(NetworkInterface)
Exceptions
IllegalArgumentException if mcastaddr is null or is a SocketAddress subclass not supported by this socket
IOException if there is an error leaving or when the address is not a multicast address.
SecurityException if a security manager exists and its checkMulticast method doesn't allow the operation.

getInterface

open fun getInterface(): InetAddress!

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

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

joinGroup

open fun joinGroup(mcastaddr: InetAddress!): Unit

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 InetAddress!: is the multicast address to join
Exceptions
IOException if there is an error joining or when the address is not a multicast address.
SecurityException if a security manager exists and its checkMulticast method doesn't allow the join.

joinGroup

added in API level 1.4
open fun joinGroup(mcastaddr: SocketAddress!, netIf: NetworkInterface!): Unit

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 SocketAddress!: is the multicast address to join
netIf SocketAddress!: specifies the local interface to receive multicast datagram packets, or null to defer to the interface set by MulticastSocket#setInterface(InetAddress) or MulticastSocket#setNetworkInterface(NetworkInterface)
Exceptions
IllegalArgumentException if mcastaddr is null or is a SocketAddress subclass not supported by this socket
IOException if there is an error joining or when the address is not a multicast address.
SecurityException if a security manager exists and its checkMulticast method doesn't allow the join.

getTimeToLive

open fun getTimeToLive(): Int

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

Return
Int: the default time-to-live value
Exceptions
IOException if an I/O exception occurs while getting the default time-to-live value

getNetworkInterface

added in API level 1.4
open fun getNetworkInterface(): NetworkInterface!

Get the multicast network interface set.

Return
NetworkInterface!: the multicast NetworkInterface currently set
Exceptions
SocketException if there is an error in the underlying protocol, such as a TCP error.

getLoopbackMode

added in API level 1.4
open fun getLoopbackMode(): Boolean

Get the setting for local loopback of multicast datagrams.

Return
Boolean: true if the LoopbackMode has been disabled
Exceptions
SocketException if an error occurs while getting the value

See Also

setInterface

open fun setInterface(inf: InetAddress!): Unit

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 InetAddress!: the InetAddress
Exceptions
SocketException if there is an error in the underlying protocol, such as a TCP error.

See Also

send

open fun send(p: DatagramPacket!, ttl: Byte): Unit

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 DatagramPacket!: 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 DatagramPacket!: optional time to live for multicast packet. default ttl is 1.
Exceptions
IOException is raised if an error occurs i.e error while setting ttl.
SecurityException if a security manager exists and its checkMulticast or checkConnect method doesn't allow the send.