“get the information from the remote site and using the cookie generated by that URL”
The inbuilt WM service pub.client:http flow service should give you this functionality. If you need to extract the cookie, I think you can inspect the header/lines output of pub.client:http to get at the HTTP headers from the remote server. If you just want to use the cookie, I think multiple invokes to pub.client:http automatically reuses the cookies from the remote server (not 100% sure about how this works).
For getting the cookie used by a client posting to your IS server (i.e. the reverse of the above), the pub.flow:getTransportInfo service comes in handy.