websocket-close-codes/README.md

WebSocket close codes

Close code (uint16)	Codename	Internal	Customizable	Description
0 - 999	-	Yes	No	Unused
1000	CLOSE_NORMAL	No	No	Successful operation / regular socket shutdown
1001	CLOSE_GOING_AWAY	No	No	An endpoint is leaving (browser tab closing)
1002	CLOSE_PROTOCOL_ERROR	Yes	No	Endpoint received a malformed frame
1003	CLOSE_UNSUPPORTED	Yes	No	Endpoint received an unsupported frame
1004		Yes	No	Reserved
1005	CLOSED_NO_STATUS	Yes	No	Expected close status, received none
1006	CLOSE_ABNORMAL	Yes	No	No close code frame has been receieved
1007	Unsupported Data	No	No	Endpoint received inconsistent message (e.g. malformed UTF-8)
1008	Policy Violation	No	No	Generic code used for situations other than 1003 and 1009
1009	CLOSE_TOO_LARGE	No	No	Endpoint won't process large frame
1010	Missing Extension	No	No	Client wanted an extension which server did not reply with
1011	Internal Error	Yes	No	Internal server error while operating
1012	Service Restart	No	No	Server/service is restarting
1013	Server Overload/Try Again Later	No	No	Try Again Later code; temporary server condition forced to block client's request
1014	Bad Gateway	No	No	Server acting as gateway received an invalid response
1015	TLS Handshake Fail	Yes	No	TLS handshake failure
1016 - 1999		Yes	No	Reserved for later
2000 - 2999		Yes	No	Reserved for websocket extensions
3000 - 3999		Yes	Yes	Reserved for frameworks / extensions, can be registered first come first serve at IANA
4000 - 4999		No	Yes	Available for applications