This can also be done with Ethereal but that requires some TCP/IP knowledge.
Download tcpmon.jar from here
and run as:
java -jar tcpmon.jar
This will bring up the screen with:
Local Port: 8080
Server Name: 127.0.0.1
Server Port: 80
Assume that the web service address that the client uses is
Change this in the client to
Then change the Server Name to a.b.c.d and change the Server Port to 9090.
Then "Add Monitor"
So now your client will send to port 8080 and tcpmon will pick this up and redirect to a.b.c.d:9090 thus trapping the messages and then displaying them