How to get the file name in OSB !2c using file protocol

Question

Problem Summary

Unable to get filename in OSB 12c using File Protocol

Problem Description

We have the below useCase in OSB 12c

1. Read File using OSB proxy Service using File Protocol, Service Type as Messaging Service, Request Type as Binary
2. get the file name
3. do java callout
4. write file using Business Service

In Step 2 - we are unable to get the file name, we have tried the below in the request pipeline

$inbound/ctx:transport/ctx:request/tp:headers/file:fileName $inbound/ctx:transport/ctx:response/file:filePath $inbound/ctx:transport/ctx:request/tp:headers/jca:jca.file.FileName

for all of them we are getting null

any help would be great