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  5. Multicast Transport Reference

Multicast Module Reference

Introduction

The Multicast transport allow sending messages to or receiving messages from groups of multicast sockets. It is implemented on top of UDP and is highly scalable since knowledge of the receivers is not required.

Namespace and Syntax

XML namespace:

xmlns:multicast="http://www.mulesoft.org/schema/mule/multicast"

XML Schema location:

http://www.mulesoft.org/schema/mule/multicast http://www.mulesoft.org/schema/mule/multicast/3.2/mule-multicast.xsd

Connector syntax:

<multicast:connector name="mcConnector" receiveBufferSize="1024" sendBufferSize="1024"               timeout="0" keepSendSocketOpen="false" broadcast="false"               timeToLive="127" loopback="true'/>

Endpoint syntax: You can define your endpoints two different ways:

  1. Prefixed endpoint:

<multicast:inbound-endpoint host="localhost" port="65433"/>

  1. Non-prefixed URI:

<inbound-endpoint address="multicast://localhost:65433"/>

See the sections below for more information.

Considerations

IP Multicasting is a service provided by IP (the internet protocol layer), that allows one-to-many communication. The most common use of IP Multicasting is to send UDP datagrams to multiple sockets located on different systems. Mule supports this with the Multicast transport. Note that, except for the communication being many-to-one instead of one-to-one, the Multicast transport is very similar to the UDP transport and the same considerations should be observed.

As shown in the examples below, the Multicast transport has two purposes:

  • Send messages to a group of IP Multicasting sockets

  • Read messages sent to a group of IP Multicasting sockets

Features

The Multicasting module allows a Mule application both to send and receive IP Multicasting datagrams, and to declaratively customize the following features of IP Multicasting (with the standard name for each feature, where applicable):

  • The timeout for sending or receiving messages (SO_TIMEOUT).

  • Whether to allow sending broadcast messages (SO_BROADCAST).

  • Whether to close a socket after sending a message.

  • The maximum size of messages that can be received.

  • The time to live for the packets that are sent.

  • Whether to loop packets back to the local socket.

Multicast endpoints can be used in one of two ways:

  • To receive an IP Multicasting datagram, create an inbound Multicast endpoint.

  • To send an IP Multicasting datagram, create an outbound Multicast endpoint.

Usage

To use Multicast endpoints

<multicast:connector name="multicastConnector"/>

  • Create Multicast endpoints.

    • Datagrams are received on inbound endpoints. The bytes in the datagram become the message payload.

    • Datagrams are sent to outbound endpoints. The bytes in the message payload become the datagram.

    • Both kinds of endpoints are identified by a host name and a port. The host name, in this case, is one of the standard IP multicast addresses defined here. When a datagram is sent to a multicasting host/port combination, all sockets subscribed to that host and port receive the message.

Multicast endpoints are always one-way.

Example Configurations

Mule Flow

Copy datagrams from one port to another in a flow

<multicast:connector name="connector"/> ❶<flow name="copy">    <multicast:inbound-endpoint host="224.0.0.0" port="4444" exchange-pattern="one-way"/> ❷    <pass-through-router>        <multicast:outbound-endpoint host="224.0.0.0" port="5555" exchange-pattern="one-way" /> ❸    </pass-through-router></flow>

Mule Service

Copy datagrams from one port to another in a service

<multicast:connector name="connector"/> ❶<service name="copy>    <inbound>        <multicast:inbound-endpoint host="224.0.0.0" port="4444" exchange-pattern="one-way"/> ❷    </inbound>    <outbound>        <multicast:outbound-endpoint host="224.0.0.0" port="5555" exchange-pattern="one-way" /> ❸    </outbound></service>

Configuration Options

Multicast Connector attributes

Name Description Default

broadcast

Set to true to allow sending to broadcast ports.

false

keepSendSocketOpen

Whether to keep the the socket open after sending a message.

false

loopback

Whether to loop messages back to the socket that sent them.

false

receiveBufferSize

The size of the largest (in bytes) datagram that can be received.

16 Kbytes

sendBufferSize

The size of the network send buffer.

16 Kbytes

timeout

The timeout used for both sending and receiving.

system default

timeToLive

How long the packet stays active. This is a number between 1 and 225.

System default

Configuration Reference

Element Listing

Multicast Transport

The Multicast transport can dispatch Mule events using IP multicasting.

Connector

Inbound endpoint

Attributes of <inbound-endpoint…​>

Name Type Required Default Description

host

string

no

port

port number

no

No Child Elements of <inbound-endpoint…​>

Outbound endpoint

Attributes of <outbound-endpoint…​>

Name Type Required

Default

Description

host

string

no

port

port number

no

No Child Elements of <outbound-endpoint…​>

Endpoint

Attributes of <endpoint…​>

Name Type Required Default Description

host

string

no

port

port number

no

No Child Elements of <endpoint…​>

Schema

Javadoc API Reference

The Javadoc for this module can be found here: Multicast

Maven

The Multicast Module can be included with the following dependency:

<dependency>  <groupId>org.mule.transports</groupId>  <artifactId>mule-transport-multicast</artifactId>  <version>3.2.0</version></dependency>

Extending the Multicast Transport

Best Practices

Notes

Before Mule 3.1.1, there were two different attributes for setting timeout on Multicast connectors, sendTimeout and receiveTimeout. It was necessary to set them to the same value. Now there is only timeout for either send or receive.