WebSocket: close() method

Available in workers

The WebSocket.close() method closes the WebSocket connection or connection attempt, if any. If the connection is already CLOSED, this method does nothing.

[!NOTE] The process of closing the connection begins with a closing handshake, and the close() method does not discard previously-sent messages before starting that closing handshake; even if the user agent is still busy sending those messages, the handshake will only start after the messages are sent.

Syntax

close()
close(code)
close(code, reason)

Parameters

• code Optional

  • : An integer WebSocket connection close code value indicating a reason for closure:
    • If unspecified, a close code for the connection is automatically set: to 1000 for a normal closure, or otherwise to another standard value in the range 1001-1015 that indicates the actual reason the connection was closed.
    • If specified, the value of this code parameter overrides the automatic setting of the close code for the connection, and instead sets a custom code. The value must be an integer: either 1000, or else a custom code of your choosing in the range 3000-4999. If you specify a code value, you should also specify a reason value.

• reason Optional

  • : A string providing a custom WebSocket connection close reason (a concise human-readable prose explanation for the closure). The value must be no longer than 123 bytes (encoded in UTF-8).

    [!NOTE] Because UTF-8 uses two to four bytes to encode any non-ASCII characters, a 123-character reason value containing non-ASCII characters would exceed the 123-byte limit.

    If you specify a reason value, you should also specify a code value.

Return value

None (undefined).

Exceptions

• InvalidAccessError DOMException
  • : Thrown if code is neither an integer equal to 1000 nor an integer in the range 3000 – 4999.
• SyntaxError DOMException
  • : Thrown if the UTF-8-encoded reason value is longer than 123 bytes.

Specifications

Browser compatibility

See also

• RFC 6455 (the WebSocket Protocol specification)