Websockets

Websockets are an asynchronous and bidirectional connection between a client and a server. Once a Websocket connection is established, either party may send messages to the other party - this unleashes truly unbounded possibilities for creating dynamic, real-time, and asynchronous applications.

Websocket requests are not routed the way HTTP requests are; instead, the mapping from incoming requests to Websocket handlers is defined in the service-map.adoc.

In the service map, the :io.pedestal.http/websockets key^[1] maps string routes to endpoint maps^[2].

The endpoint map is a set of callbacks. The path and endpoint map are ultimately passed to the api:add-endpoint[] function, which describes in detail how the callbacks are used.

Essentially, the :on-open callback is invoked when the client initiates the connection.

It is intended that, when the client connects, some form of server-side process will be initiated capable of sending messages to the client asynchronously. It is the responsibility of the :on-open callback to create such a process. One common option is to use the api:on-open-start-ws-connection[] function to create the callback, or construct the :on-open callback around the api:start-ws-connection[] function.

The :on-string and :on-binary callbacks are invoked when a text or binary message from the client is received.