nats-io/nats-server · error

http.StatusText(status)

Error message

http.StatusText(status)

What it means

The HTTP status line text produced by wsReturnHTTPError() when writing the error body via http.Error(). Not a distinct error condition: it renders the human-readable name (e.g. '403 Forbidden') of the status passed for the failed websocket handshake, accompanying the '%s - websocket handshake error: %s' error.

Source

Thrown at server/websocket.go:1025

						}
						if snc && cnc {
							return true, true
						}
					}
					return true, false
				}
			}
		}
	}
	return false, false
}

// Send an HTTP error with the given `status` to the given http response writer `w`.
// Return an error created based on the `reason` string.
func wsReturnHTTPError(w http.ResponseWriter, r *http.Request, status int, reason string) error {
	err := fmt.Errorf("%s - websocket handshake error: %s", r.RemoteAddr, reason)
	w.Header().Set("Sec-Websocket-Version", "13")
	http.Error(w, http.StatusText(status), status)
	return err
}

// If the server is configured to accept any origin, then this function returns
// `nil` without checking if the Origin is present and valid. This is also
// the case if the request does not have the Origin header.
// Otherwise, this will check that the Origin matches the same origin or
// any origin in the allowed list.
func (w *srvWebsocket) checkOrigin(r *http.Request) error {
	w.mu.RLock()
	checkSame := w.sameOrigin
	listEmpty := len(w.allowedOrigins) == 0
	w.mu.RUnlock()
	if !checkSame && listEmpty {
		return nil
	}
	origin := r.Header.Get("Origin")
	if origin == _EMPTY_ {

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Inspect the accompanying handshake error and status code to determine why the upgrade was refused
2. Fix the client request or server websocket options per the reported reason

When it happens

Trigger: Thrown at server/websocket.go:1025 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of nats-io/nats-server@3a66a489d2 (2026-09-02). Data as JSON: /api/errors/3e573824ab4d9ea1. Report an issue: GitHub.