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/3, the
following options are recognised:
- subprotocols(+List)
- List of subprotocols that are acceptable. The selected
protocol is available as ws_property(WebSocket,
subprotocol(Protocol).
Note that clients often provide an Origin header and some servers
require this field. See RFC 6455 for details. By default this
predicate does not set Origin. It may be set using the
request_header option of http_open/3, e.g. by passing this in the
Options list:
request_header('Origin' = 'https://www.swi-prolog.org')
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}.
- Arguments:
-
