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WebSocketRoute

Whenever a WebSocket route is set up with page.route_web_socket() or browser_context.route_web_socket(), the WebSocketRoute object allows to handle the WebSocket, like an actual server would do.

Mocking

By default, the routed WebSocket will not connect to the server. This way, you can mock entire communcation over the WebSocket. Here is an example that responds to a "request" with a "response".

def message_handler(ws: WebSocketRoute, message: Union[str, bytes]):
  if message == "request":
    ws.send("response")

page.route_web_socket("wss://example.com/ws", lambda ws: ws.on_message(
    lambda message: message_handler(ws, message)
))

Since we do not call web_socket_route.connect_to_server inside the WebSocket route handler, Playwright assumes that WebSocket will be mocked, and opens the WebSocket inside the page automatically.

Here is another example that handles JSON messages:

def message_handler(ws: WebSocketRoute, message: Union[str, bytes]):
  json_message = json.loads(message)
  if json_message["request"] == "question":
    ws.send(json.dumps({ "response": "answer" }))

page.route_web_socket("wss://example.com/ws", lambda ws: ws.on_message(
    lambda message: message_handler(ws, message)
))

Intercepting

Alternatively, you may want to connect to the actual server, but intercept messages in-between and modify or block them. Calling web_socket_route.connect_to_server returns a server-side WebSocketRoute instance that you can send messages to, or handle incoming messages.

Below is an example that modifies some messages sent by the page to the server. Messages sent from the server to the page are left intact, relying on the default forwarding.

def message_handler(server: WebSocketRoute, message: Union[str, bytes]):
  if message == "request":
    server.send("request2")
  else:
    server.send(message)

def handler(ws: WebSocketRoute):
  server = ws.connect_to_server()
  ws.on_message(lambda message: message_handler(server, message))

page.route_web_socket("/ws", handler)

After connecting to the server, all messages are forwarded between the page and the server by default.

However, if you call web_socket_route.on_message() on the original route, messages from the page to the server will not be forwarded anymore, but should instead be handled by the handler.

Similarly, calling web_socket_route.on_message() on the server-side WebSocket will stop forwarding messages from the server to the page, and handler should take care of them.

The following example blocks some messages in both directions. Since it calls web_socket_route.on_message() in both directions, there is no automatic forwarding at all.

def ws_message_handler(server: WebSocketRoute, message: Union[str, bytes]):
  if message != "blocked-from-the-page":
    server.send(message)

def server_message_handler(ws: WebSocketRoute, message: Union[str, bytes]):
  if message != "blocked-from-the-server":
    ws.send(message)

def handler(ws: WebSocketRoute):
  server = ws.connect_to_server()
  ws.on_message(lambda message: ws_message_handler(server, message))
  server.on_message(lambda message: server_message_handler(ws, message))

page.route_web_socket("/ws", handler)

Methods​

close​

Added in: v1.48 webSocketRoute.close

Closes one side of the WebSocket connection.

Usage

web_socket_route.close()
web_socket_route.close(**kwargs)

Arguments

Returns

on_close​

Added in: v1.48 webSocketRoute.on_close

Allows to handle WebSocket.close.

By default, closing one side of the connection, either in the page or on the server, will close the other side. However, when web_socket_route.on_close() handler is set up, the default forwarding of closure is disabled, and handler should take care of it.

Usage

web_socket_route.on_close(handler)

Arguments

on_message​

Added in: v1.48 webSocketRoute.on_message

This method allows to handle messages that are sent by the WebSocket, either from the page or from the server.

When called on the original WebSocket route, this method handles messages sent from the page. You can handle this messages by responding to them with web_socket_route.send(), forwarding them to the server-side connection returned by web_socket_route.connect_to_server or do something else.

Once this method is called, messages are not automatically forwarded to the server or to the page - you should do that manually by calling web_socket_route.send(). See examples at the top for more details.

Calling this method again will override the handler with a new one.

Usage

web_socket_route.on_message(handler)

Arguments

send​

Added in: v1.48 webSocketRoute.send

Sends a message to the WebSocket. When called on the original WebSocket, sends the message to the page. When called on the result of web_socket_route.connect_to_server, sends the message to the server. See examples at the top for more details.

Usage

web_socket_route.send(message)

Arguments

Properties​

connect_to_server​

Added in: v1.48 webSocketRoute.connect_to_server

By default, routed WebSocket does not connect to the server, so you can mock entire WebSocket communication. This method connects to the actual WebSocket server, and returns the server-side WebSocketRoute instance, giving the ability to send and receive messages from the server.

Once connected to the server:

See examples at the top for more details.

Usage

web_socket_route.connect_to_server

Returns

url​

Added in: v1.48 webSocketRoute.url

URL of the WebSocket created in the page.

Usage

web_socket_route.url

Returns