http_open_websocket/3

Documentation
- Reference manual
- Packages
  - SWI-Prolog HTTP support
    - library(http/websocket): WebSocket support

Availability::- use_module(library(http/websocket)).

[det]http_open_websocket(+URL, -WebSocket, +Options)

Establish a client websocket connection. This predicate calls http_open/3 with additional headers to negotiate a websocket connection. In addition to the options processed by http_open, the following options are recognised:

subprotocols(+List): List of subprotocols that are acceptable. The selected protocol is available as ws_property(WebSocket, subprotocol(Protocol).

The following example exchanges a message with the html5rocks.websocket.org echo service:

?- URL = 'ws://html5rocks.websocket.org/echo',
   http_open_websocket(URL, WS, []),
   ws_send(WS, text('Hello World!')),
   ws_receive(WS, Reply),
   ws_close(WS, 1000, "Goodbye").
URL = 'ws://html5rocks.websocket.org/echo',
WS = <stream>(0xe4a440,0xe4a610),
Reply = websocket{data:"Hello World!", opcode:text}.

WebSocket

is a stream pair (see stream_pair/3)