The WebService, HTTPService, and RemoteObject components use the Flex logging framework, which can greatly assist debugging applications. Messages are automatically logged to the Flex logging framework, so you won’t need to enable the components to explicitly begin logging. Messages that are logged are within the mx.messaging.* filter. Example 18-4 is an HTTPService call with a TraceTarget that will show only log messages related to the server calls.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
initialize="initializeHandler()">
        <mx:Script>
        <![CDATA[
            import mx.logging.Log;
            import mx.logging.targets.TraceTarget;

            private var _target:TraceTarget;

            private function initializeHandler():void
            {
                _target = new TraceTarget();
                _target.includeTime = true;
                _target.includeLevel = true;
                _target.includeCategory = true;
                _target.filters = ["mx.messaging.*"];
                Log.addTarget(_target);
            }

            private function sendToLog():void
            {
                Log.getLogger("com.oreilly.programmingflex.Logging").
info("Log Message");
            }
        ]]>
    </mx:Script>
    <mx:Button click="sendToLog()" label="Log Message"/>
    <mx:Button click="service.send();" label="Send HTTPService"/>
    <mx:HTTPService id="service" url="http://www.w3c.org"/>
</mx:Application>

This example will log messages from the HTTPService but not from the button click handler, which can be very useful when you are working with a larger application and you are interested in viewing only the log information from the mx.rpc components. The server component logs useful information on both the data that is being sent and received, as well as the information that can be used for profiling messaging performance. For the WebService component, this can be especially useful in gauging Flex’s performance in terms of serializing and deserializing SOAP messages.

When debugging network programming code, using a data inspector (packet sniffing tools or a proxy) is invaluable. With Flex, these tools can also be very useful. Adobe does not provide such a built-in tool, but many tools exist that work with Flex. If you are already comfortable with a tool, you can continue to use that tool.

Some common network debugging tools include the following: