anchor.diff:  [[postal-servers]]
   === Is there any server supports that protocol?
   
  -At this moment the unique backend/server implementation for this library is
  +At this moment, the unique backend/server implementation for this library is
   link:https://github.com/funcool/catacumba[catacumba]. And you can find the related
   link:https://funcool.github.io/catacumba/latest/#postal[documentation] for the
   backend handlers setup.
  
positive.code: === Contributing
  
  Unlike Clojure and other Clojure contributed libraries _postal_ does not have many
  restrictions for contributions. Just open an issue or pull request.
  
  
  === Source Code
  
negative.code:           (println "User: " data)))
  ----
  
  Notice that `query` function returns a promise that will be resolved
  with the response message or rejected with a message if an `:error` message is
  returned. The promise may also be rejected with an exception object if something
  foreign to transport happens (message serialization error as an example).
  
  Additionally to query, there is also `novelty` function, that sends `:novelty`
  type frame in the same way as with `query`.
  
  == User Guide
  
  === User defined frames
  
  At this moment, the postal library only implements `query` and `novelty` specialized
  functions for send corresponding kind of frames. Surely, you may want to use
  own messages if the provided are not enough.
  
  For that purpose, *postal* library exposes a `send!` function that just exposes
  as a low level api to define your own helpers for send frames. Let us imagine you want
  to send a `:take` type message; to do so let's define a helper that uses `send!`
  function for send that frame:
  
  [source, clojure]
  