Allow server to push error message to client.

client.go

@@ -54,7 +54,13 @@ func (err protocolError) Error() string {
 	return string(err)
 }
 
-func errorToWSCloseMessage(err error) []byte {
+type userError string
+
+func (err userError) Error() string {
+	return string(err)
+}
+
+func errorToWSCloseMessage(err error) (string, []byte) {
 	var code int
 	var text string
 	switch e := err.(type) {
@@ -63,10 +69,13 @@ func errorToWSCloseMessage(err error) []byte {
 	case protocolError:
 		code = websocket.CloseProtocolError
 		text = string(e)
+	case userError:
+		code = websocket.CloseNormalClosure
+		text = string(e)
 	default:
 		code = websocket.CloseInternalServerErr
 	}
-	return websocket.FormatCloseMessage(code, text)
+	return "The server said: " + text, websocket.FormatCloseMessage(code, text)
 }
 
 func isWSNormalError(err error) bool {
@@ -82,6 +91,7 @@ type clientMessage struct {
 	Password    string                     `json:"password,omitempty"`
 	Group       string                     `json:"group,omitempty"`
 	Value       string                     `json:"value,omitempty"`
+	Message     string                     `json:"message,omitempty"`
 	Me          *bool                      `json:"me,omitempty"`
 	Offer       *webrtc.SessionDescription `json:"offer,omitempty"`
 	Answer      *webrtc.SessionDescription `json:"answer,omitempty"`
@@ -120,10 +130,15 @@ func startClient(conn *websocket.Conn) (err error) {
 		if isWSNormalError(err) {
 			err = nil
 		} else {
+			m, e := errorToWSCloseMessage(err)
+			if m != "" {
+				c.write(clientMessage{
+					Type:    "error",
+					Message: m,
+				})
+			}
 			select {
-			case c.writeCh <- closeMessage{
-				errorToWSCloseMessage(err),
-			}:
+			case c.writeCh <- closeMessage{e}:
 			case <-c.writerDone:
 			}
 		}

static/sfu.js

@@ -311,6 +311,9 @@ function serverConnect() {
             case 'chat':
                 addToChatbox(m.id, m.username, m.value, m.me);
                 break;
+            case 'error':
+                displayError(m.message);
+                break;
             default:
                 console.warn('Unexpected server message', m.type);
                 return;
@@ -773,7 +776,6 @@ document.getElementById('disconnectbutton').onclick = function(e) {
     socket.close();
 }
 
-
 function start() {
     group = decodeURIComponent(location.pathname.replace(/^\/[a-z]*\//, ''));
     let title = document.getElementById('title');