Error -26547: Authentication required

I having some issues with the scripting....
 
I am performance testing an Oracle E business suit (EBS R12) .. I am using Multi Protocol Oracle NCA and Http protocol
 
I am getting below error 
 
"vuser_init.c(126): Error -26547: Authentication required, please use web_set_user, e.g. web_set_user("domain\\user", "password", "host:port");   [MsgId: MERR-26547]"
vuser_init.c(132): Error -26630: HTTP Status-Code=401 (Unauthorized) for "">http://URL"   [MsgId: MERR-26630]
 
 
I tried giving  web _set_use(details here) but even then it is not working....
 
We are not using any proxy settings while login to application.
 
Could you please help me in resolving this issue....