copy contents of a remote location to a local file in ruby script

I want to copy the contents of a remote location file to some local file after an ssh connection has been made.

 begin
    ssh = Net::SSH.start("localhost", "user")
    logger.info "conn successful!"
    results = conn.exec!('ruby somefile "#{arguments}"')
    #code to copy the contents of a.txt in remote location to local file
    #IO.copy_stream (localfile, remotefile)
 rescue
    logger.info "error - cannot connect to host"
 end

I tried using IO.copy_stream but that doesn't work. How do I go about this?