WebSocket Functions

This module contains functions for accessing specific WebSocket functions. This module is mainly useful in the context of WebSockets.

Conventions

• The module will be available if the basex-api library is found in the classpath. This is the case if you use one of the complete distributions of BaseX (zip, exe, war).
• All functions and errors are assigned to the http://basex.org/modules/ws namespace, which is statically bound to the ws prefix.
• As sessions are side-effecting operations, all functions are flagged as nondeterministic. As a result, some query optimizations will be suppressed.

General Functions

ws:id

ws:id() as xs:string

ws:ids

ws:ids() as xs:string*

ws:path

ws:path(
  $id  as xs:string
) as xs:string

ws:close

ws:close(
  $id  as xs:string
) as empty-sequence()

Sending Data

ws:send

ws:send(
  $message  as item(),
  $ids      as xs:string*
) as empty-sequence()

ws:broadcast

ws:broadcast(
  $message  as item()
) as empty-sequence()

ws:emit

ws:emit(
  $message  as item()
) as empty-sequence()

ws:eval

ws:eval(
  $query     as xs:anyAtomicType,
  $bindings  as map(*)?           := (),
  $options   as map(*)?           := {}
) as xs:string

declare
  %ws:message('/tasks', '{$message}')
function local:message($message) {
  ws:eval('prof:sleep(10000), "Your message has been processed."')
};

WebSocket Attributes

ws:get

ws:get(
  $id       as xs:string,
  $name     as xs:string,
  $default  as item()*    := ()
) as item()*

ws:set

ws:set(
  $id     as xs:string,
  $name   as xs:string,
  $value  as item()*
) as empty-sequence()

ws:delete

ws:delete(
  $id    as xs:string,
  $name  as xs:string
) as empty-sequence()

Examples

Example 1

import module namespace ws = "http://basex.org/modules/ws";

declare
  %ws:connect('/')
function local:connect() as empty-sequence() {
  let $id := ws:id()
  let $message := json:serialize({ 'type': 'Connect', 'id': $id })
  return ws:broadcast($message)
};

• The function has a %ws:connect annotation. It gets called if a client successfully creates a WebSocket connection to the path / (check out WebSockets for further information).
• A JSON response is generated, which contains the new client id and a Connect string.
• This response will be sent to all other connected clients.

Example 2

import module namespace ws = "http://basex.org/modules/ws";

declare
  %ws:message('/', '{$message}')
function local:message(
  $message as xs:string
) as empty-sequence() {
  let $message := json:serialize({ 'message': $message })
  return ws:emit($message)
};

• The function has a %ws:message annotation. It gets called if a client sends a new message.
• A JSON response is generated, which contains the message string.
• This response will be sent to all connected clients (including the calling client).

Errors

Changelog

• Added: ws:eval

• Added: New module added.