How to monitor messages using tcpmon in Axis2 dual channel web service invocation

Apache Axis2 client API provides the necessary methods to utilize a service using two transport channels. You can even send request through one transport (e.g:- HTTP) and get the response back via a different transport such as TCP.

setUseSeperateListener(boolean) method of org.apache.axis2.client.Options
class can be used to utilize a separate listener for your response.
If two separate HTTP transport channels are used for request and response, Axis2 starts a new HTTP listener at the client side to receive the incoming response message.

As most of web service developers know, Apache tcpmon can be used to monitor message flow between web service invocations. In one way messaging, it is quite straightforward.
You just need to configure tcpmon to listen in some port and direct the messages to the port where the web service is hosted. In client, port of the endpoint reference has to be changed to tcpmonitor listen port. That's all you have to do for monitoring messages in single channel invocation.

In this post, you can see how tcpmonitor is configured to use in dual channel invocation.

1. If you have not done it yet, download Apache tcpmon from here
Unzip the downloaded file and run build/tcpmon.bat {sh}

2. As I stated before, Axis2 starts a http listener at the client in dual channel invocation. Therefore, you need to configure Axis2.xml to redirect messages to tcpmon as follows.

Open AXIS2_HOME/conf/axis2.xml and locate to the following section.

<!-- ============================================ -->
<!-- Transport Ins -->
<!-- ============================================ -->
<transportReceiver name="http"
class="org.apache.axis2.transport.http.SimpleHTTPServer">
<parameter name="port">8080</parameter>
<!-- Here is the complete list of supported parameters (see example settings further below):
port: the port to listen on (default 6060)
hostname: if non-null, url prefix used in reply-to endpoint references (default null)
------------
-->
<parameter name="hostname">http://localhost:8090</parameter>
<!-- <parameter name="originServer">My-Server/1.1</parameter> -->
----------
</transportReceiver>

3. Note the highlighted elements in the above axis2.xml configuration. First you have to uncomment the hostname paramter <parameter name="hostname"> and specify a port which is not already listened in your system (e.g:- 8090).

In tcpmon, create a new listener with 8090 as the listen port and 8080 as the target port. With this configuration, the response messages receive to the reply-to endpoint reference are directed to 8090 tcpmon port and then those will be targeted to client HTTP listener port, 8080.



Now, you should be able to monitor the response flow in dual channel invocation.