11.4 Autoconfiguring Listeners

You may choose to autoconfigure your HTTP and HTTPS listener. Autoconfiguration may be useful for several reasons -- for instance, to avoid binding a listener to a port already in use, or to allow your service to be moved to a different machine without having to revise the configuration files.

Once the listener has been bound to a local address (in the rwsf::MessageListener::start() method), the "bound-host", "bound-ip", and "bound-port" properties are set to the host name, ip address, and port of the address. For example, let's look at the client configuration file client-transports.xml for HTTP.

<rwsf:listener name="HTTP"
  uri="http://schemas.xmlsoap.org/soap/listener/http" scheme="http"
  default="true" class="rwsf_webservice.createHttpMessageListener">      
   <rwsf:property name="auto-start" value="false"/>               
   <!-- When host and port listener properties are absent, 
         they will be auto-configured to the machine's host name 
         and first available port. The machine will need to be
         configured for lookup on the network under its host name. -->
   <rwsf:property name="host" value="localhost"/> 
   <!-- <rwsf:property name="port" value="9000"/> -->
   <rwsf:property name="request-backlog" value="5"/>
   <rwsf:property name="request-timeout" value="60000"/>
   <rwsf:property name="request-buffersize" value="4096"/>
   <rwsf:property name="keep-alive" value="true"/>
 </rwsf:listener>

Note that the "port" property is commented out, allowing the listener location to be dynamically assigned. If you do not want a dynamic assignment, uncomment this property and enter a value.

Another way to implement auto-assignment is to comment out the host property. In other words, your applications could have a fixed host with an automatically-assigned port, or a fixed port, with an automatically-assigned host.

(The bound-host, bound-port, and bound-ip properties will also reflect these values.)

It is easy to use an auto-configured listener in your applications. Following is an excerpt from ForecastClient.cpp, the provided sample implementation in the Forecast example implementing listener auto-configuration. (This example is located in your <installdir>\examples\webservices\Forecast directory.)

...
void invoke_notifyMe(ForecastProxy& proxy,  
                     rwsf::MessageListener listener)
{
  std::string host_in(listener.getProperty("bound-ip"));
  std::string port_in(listener.getProperty("bound-port"));
  std::string transportName_in(listener.getProperty("name"));
...

Note the call listener.getProperty("bound-ip") and listener.getProperty("bound-port"). These calls return the auto-configured values for the IP address and the port.

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