Swagger2::Guides::WebSocket(3) How to expose Swagger over WebSockets


This guide will show how to expose a Swagger API over WebSockets.

This feature is EXPERIMENTAL and is subject to change.

See <https://github.com/jhthorsen/swagger2/blob/master/examples/websocket.pl> for a working example.


This way of exposing Swagger over WebSockets is in no way compatible with <https://github.com/swagger-api/swagger-socket>.



  package MyApp;
  use Mojo::Base "Mojolicious";
  sub startup {
    my $app = shift;
    my $ws = $app->routes->websocket("/ws")->to("events#ws");
    $app->plugin(Swagger2 => {
      url => app->home->rel_file("api.yaml"),
      ws  => $ws,

In the example application class above, we create a custom route object for handling the WebSocket request. The route object $ws is then passed on to the plugin and set up with a default route variable swagger.

The reason why we create a custom websocket route is so it can be used bi-directional, instead of just dispatching to Swagger actions.


  package MyApp::Controller::Events;
  sub ws {
    my $c = shift;
    $c->on(json => sub {
      my ($c, $data) = @_;
      return if $c->dispatch_to_swagger($data);

In the example controller above we listen to a json event which can dispatch_to_swagger.

This method will return boolean true if the input looks like a Swagger request.


The input data to the WebSocket need to be JSON and look like this:

    "id": "some unique string",
    "op": "operationId",
    "params": {
      "paramerName": "value"

The ``id'' is used to map the response to a unique request. This means that the ``id'' need to be generated on the client side. The uniqueness requirement is only for this WebSocket connection.

``op'' need to match an operationId in the Swagger specification.

``params'' must be an object where the keys match the parameters in the Swagger specification.


    "id": "some unique string",
    "code": 200,
    "body": {"any":"thing"}

The response contains the input ``id'', the HTTP status ``code'' and the response from the Swagger action inside ``body''.

JavaScript example

Here is an example JavaScript which can communicate over the socket:

  var ws = new WebSocket("ws://example.com/ws");
  ws.onopen = function () {
      id:   "42",
      op:   "listPets",
      args: {limit: 60}
  ws.onmessage = function (e) {
    var data = JSON.parse(e.data);
    if (data.id == "42") {
      // Response from the request above, because of matching "id"
      console.log(data.code, data.body);


  • ``x-mojo-around-action'' is ignored when issuing WebSocket requests. This may be changed in future version.
  • Sharing a WebSocket route object between multiple Swagger plugins is unsupported. (The outcome is unknown)
  • The protocol and implementation is subject for change. feedback <https://github.com/jhthorsen/swagger2/issues> is highly appreciated.


Jan Henning Thorsen - "[email protected]"