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Chapter 108. Sip

SIP Component

Available as of Camel 2.5
The sip component in Camel is a communication component, based on the Jain SIP implementation (available under the JCP license).
Session Initiation Protocol (SIP) is an IETF-defined signaling protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP).The SIP protocol is an Application Layer protocol designed to be independent of the underlying transport layer; it can run on Transmission Control Protocol (TCP), User Datagram Protocol (UDP) or Stream Control Transmission Protocol (SCTP).
The Jain SIP implementation supports TCP and UDP only.
The Camel SIP component only supports the SIP Publish and Subscribe capability as described in the RFC3903 - Session Initiation Protocol (SIP) Extension for Event
This camel component supports both producer and consumer endpoints.
Camel SIP Producers (Event Publishers) and SIP Consumers (Event Subscribers) communicate event & state information to each other using an intermediary entity called a SIP Presence Agent (a stateful brokering entity).
For SIP based communication, a SIP Stack with a listener must be instantiated on both the SIP Producer and Consumer (using separate ports if using localhost). This is necessary in order to support the handshakes & acknowledgements exchanged between the SIP Stacks during communication.
Maven users will need to add the following dependency to their pom.xml for this component: 
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-sip</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

The URI scheme for a sip endpoint is as follows: 
sip://johndoe@localhost:99999[?options]
sips://johndoe@localhost:99999/[?options]
This component supports producer and consumer endpoints for both TCP and UDP.
You can append query options to the URI in the following format, ?option=value&option=value&...

Options

The SIP Component offers an extensive set of configuration options & capability to create custom stateful headers needed to propagate state via the SIP protocol.
Name Default Value Description
stackName NAME_NOT_SET Name of the SIP Stack instance associated with an SIP Endpoint.
transport tcp Setting for choice of transport potocol. Valid choices are "tcp" or "udp".
fromUser Username of the message originator. Mandatory setting unless a registry based custom FromHeader is specified.
fromHost Hostname of the message originator. Mandatory setting unless a registry based FromHeader is specified
fromPort Port of the message originator. Mandatory setting unless a registry based FromHeader is specified
toUser Username of the message receiver. Mandatory setting unless a registry based custom ToHeader is specified.
toHost Hostname of the message receiver. Mandatory setting unless a registry based ToHeader is specified
toPort Portname of the message receiver. Mandatory setting unless a registry based ToHeader is specified
maxforwards 0 the number of intermediaries that may forward the message to the message receiver. Optional setting. May alternatively be set using as registry based MaxForwardsHeader
eventId Setting for a String based event Id. Mandatory setting unless a registry based FromHeader is specified
eventHeaderName Setting for a String based event Id. Mandatory setting unless a registry based FromHeader is specified
maxMessageSize 1048576 Setting for maximum allowed Message size in bytes.
cacheConnections false Should connections be cached by the SipStack to reduce cost of connection creation. This is useful if the connection is used for long running conversations.
consumer false This setting is used to determine whether the kind of header (FromHeader,ToHeader etc) that needs to be created for this endpoint
automaticDialogSupport off Setting to specify whether every communication should be associated with a dialog.
contentType text Setting for contentType can be set to any valid MimeType.
contentSubType xml Setting for contentSubType can be set to any valid MimeSubType.
receiveTimeoutMillis 10000 Setting for specifying amount of time to wait for a Response and/or Acknowledgement can be received from another SIP stack
useRouterForAllUris false This setting is used when requests are sent to the Presence Agent via a proxy.
msgExpiration 3600 The amount of time a message received at an endpoint is considered valid
presenceAgent false This setting is used to distingish between a Presence Agent & a consumer. This is due to the fact that the SIP Camel component ships with a basic Presence Agent (for testing purposes only). Consumers have to set this flag to true.

Registry based Options

SIP requires a number of headers to be sent/received as part of a request. These SIP header can be enlisted in the Registry, such as in the Spring XML file.
The values that could be passed in, are the following:
Name Description
fromHeader a custom Header object containing message originator settings. Must implement the type javax.sip.header.FromHeader
toHeader a custom Header object containing message receiver settings. Must implement the type javax.sip.header.ToHeader
viaHeaders List of custom Header objects of the type javax.sip.header.ViaHeader. Each ViaHeader containing a proxy address for request forwarding. (Note this header is automatically updated by each proxy when the request arrives at its listener)
contentTypeHeader a custom Header object containing message content details. Must implement the type javax.sip.header.ContentTypeHeader
callIdHeader a custom Header object containing call details. Must implement the type javax.sip.header.CallIdHeader
maxForwardsHeader a custom Header object containing details on maximum proxy forwards. This header places a limit on the viaHeaders possible. Must implement the type javax.sip.header.MaxForwardsHeader
eventHeader a custom Header object containing event details. Must implement the type javax.sip.header.EventHeader
contactHeader an optional custom Header object containing verbose contact details (email, phone number etc). Must implement the type javax.sip.header.ContactHeader
expiresHeader a custom Header object containing message expiration details. Must implement the type javax.sip.header.ExpiresHeader
extensionHeader a custom Header object containing user/application specific details. Must implement the type javax.sip.header.ExtensionHeader

Sending Messages to/from a SIP endpoint

Creating a Camel SIP Publisher

In the example below, a SIP Publisher is created to send SIP Event publications to a user "agent@localhost:5152". This is the address of the SIP Presence Agent which acts as a broker between the SIP Publisher and Subscriber
  • using a SIP Stack named client
  • using a registry based eventHeader called evtHdrName
  • using a registry based eventId called evtId
  • from a SIP Stack with Listener set up as user2@localhost:3534
  • The Event being published is EVENT_A
  • A Mandatory Header called REQUEST_METHOD is set to Request.Publish thereby setting up the endpoint as a Event publisher" 
producerTemplate.sendBodyAndHeader(  
    "sip://agent@localhost:5152?stackName=client&eventHeaderName=evtHdrName&eventId=evtid&fromUser=user2&fromHost=localhost&fromPort=3534",   
    "EVENT_A",  
    "REQUEST_METHOD",   
    Request.PUBLISH);

Creating a Camel SIP Subscriber

In the example below, a SIP Subscriber is created to receive SIP Event publications sent to a user "johndoe@localhost:5154"
  • using a SIP Stack named Subscriber
  • registering with a Presence Agent user called agent@localhost:5152
  • using a registry based eventHeader called evtHdrName. The evtHdrName contains the Event which is se to "Event_A"
  • using a registry based eventId called evtId 
@Override  
protected RouteBuilder createRouteBuilder() throws Exception {  
    return new RouteBuilder() {  
        @Override  
        public void configure() throws Exception {    
            // Create PresenceAgent  
            from("sip://agent@localhost:5152?stackName=PresenceAgent&presenceAgent=true&eventHeaderName=evtHdrName&eventId=evtid")  
                .to("mock:neverland");  
                  
            // Create Sip Consumer(Event Subscriber)  
            from("sip://johndoe@localhost:5154?stackName=Subscriber&toUser=agent&toHost=localhost&toPort=5152&eventHeaderName=evtHdrName&eventId=evtid")  
                .to("log:ReceivedEvent?level=DEBUG")  
                .to("mock:notification");  
                  
        }  
    };  
}
The Camel SIP component also ships with a Presence Agent that is meant to be used for Testing and Demo purposes only. An example of instantiating a Presence Agent is given above.
Note that the Presence Agent is set up as a user agent@localhost:5152 and is capable of communicating with both Publisher as well as Subscriber. It has a separate SIP stackName distinct from Publisher as well as Subscriber. While it is set up as a Camel Consumer, it does not actually send any messages along the route to the endpoint "mock:neverland".