Where is a access log

[Kriangyut Wangjitman]

Hi
 
Anyone knows where to find the access log? 
I’ve created a web service proxy using synapse. Sometime my friend's ws client 
(create by .net) cannot connect to the esb.
They found the error: “connection was closed”. And there is no message logged 
in synapse log file.
I want to make sure that my friend’s client can connect to my ESB.
 
Thank you
Heng