WebSocket status codes specified in RFC-6455.
RFC-6455 The WebSocket Protocol, December 2011:
https://tools.ietf.org/html/rfc6455#section-7.4.1
WebSocket Protocol Registries, April 2019:
https://www.iana.org/assignments/websocket/websocket.xhtml
7.4.1. Defined Status Codes
Endpoints MAY use the following pre-defined status codes when sending
a Close frame.
1000
1000 indicates a normal closure, meaning that the purpose for
which the connection was established has been fulfilled.
1001
1001 indicates that an endpoint is "going away", such as a server
going down or a browser having navigated away from a page.
1002
1002 indicates that an endpoint is terminating the connection due
to a protocol error.
1003
1003 indicates that an endpoint is terminating the connection
because it has received a type of data it cannot accept (e.g., an
endpoint that understands only text data MAY send this if it
receives a binary message).
1004
Reserved. The specific meaning might be defined in the future.
1005
1005 is a reserved value and MUST NOT be set as a status code in a
Close control frame by an endpoint. It is designated for use in
applications expecting a status code to indicate that no status
code was actually present.
1006
1006 is a reserved value and MUST NOT be set as a status code in a
Close control frame by an endpoint. It is designated for use in
applications expecting a status code to indicate that the
connection was closed abnormally, e.g., without sending or
receiving a Close control frame.
1007
1007 indicates that an endpoint is terminating the connection
because it has received data within a message that was not
consistent with the type of the message (e.g., non-UTF-8 [RFC3629]
data within a text message).
1008
1008 indicates that an endpoint is terminating the connection
because it has received a message that violates its policy. This
is a generic status code that can be returned when there is no
other more suitable status code (e.g., 1003 or 1009) or if there
is a need to hide specific details about the policy.
1009
1009 indicates that an endpoint is terminating the connection
because it has received a message that is too big for it to
process.
1010
1010 indicates that an endpoint (client) is terminating the
connection because it has expected the server to negotiate one or
more extension, but the server didn't return them in the response
message of the WebSocket handshake. The list of extensions that
are needed SHOULD appear in the /reason/ part of the Close frame.
Note that this status code is not used by the server, because it
can fail the WebSocket handshake instead.
1011
1011 indicates that a server is terminating the connection because
it encountered an unexpected condition that prevented it from
fulfilling the request.
1012 (IANA Registry, Non RFC-6455)
1012 indicates that the service is restarted. a client may reconnect,
and if it choses to do, should reconnect using a randomized delay
of 5 - 30 seconds.
1013 (IANA Registry, Non RFC-6455)
1013 indicates that the service is experiencing overload. a client
should only connect to a different IP (when there are multiple for the
target) or reconnect to the same IP upon user action.
1014 (IANA Registry, Non RFC-6455)
The server was acting as a gateway or proxy and received an invalid
response from the upstream server. This is similar to 502 HTTP Status Code.
1015
1015 is a reserved value and MUST NOT be set as a status code in a
Close control frame by an endpoint. It is designated for use in
applications expecting a status code to indicate that the
connection was closed due to a failure to perform a TLS handshake
(e.g., the server certificate can't be verified).
7.4.2. Reserved Status Code Ranges
0-999
Status codes in the range 0-999 are not used.
1000-2999
Status codes in the range 1000-2999 are reserved for definition by
this protocol, its future revisions, and extensions specified in a
permanent and readily available public specification.
3000-3999
Status codes in the range 3000-3999 are reserved for use by
libraries, frameworks, and applications. These status codes are
registered directly with IANA. The interpretation of these codes
is undefined by this protocol.
4000-4999
Status codes in the range 4000-4999 are reserved for private use
and thus can't be registered. Such codes can be used by prior
agreements between WebSocket applications. The interpretation of
these codes is undefined by this protocol.
While WebSocketCloseStatus is enum-like structure, its instances should NOT be compared by reference.
Instead, either equals(Object) should be used or direct comparison of code() value.
