webrtc: on browsers, display error messages from server

internal/protocols/webrtc/peer_connection.go

@@ -311,7 +311,7 @@
 	answer, err := co.wr.CreateAnswer(nil)
 	if err != nil {
 		if errors.Is(err, webrtc.ErrSenderWithNoCodecs) {
-			return nil, fmt.Errorf("track codecs are not supported by remote")
+			return nil, fmt.Errorf("codecs not supported by client")
 		}
 		return nil, err
 	}

internal/servers/webrtc/publish_index.html

@@ -409,7 +409,7 @@
 	})
 		.then((res) => {
 			if (res.status !== 204) {
-				throw new Error('bad status code');
+				throw new Error(`bad status code ${res.status}`);
 			}
 		})
 		.catch((err) => {
@@ -464,13 +464,20 @@
 		body: offer,
 	})
 		.then((res) => {
-			if (res.status !== 201) {
-				throw new Error('bad status code');
+			switch (res.status) {
+			case 201:
+				break;
+			case 400:
+				return res.json().then((e) => { throw new Error(e.error); });
+			default:
+				throw new Error(`bad status code ${res.status}`);
 			}
+
 			sessionUrl = new URL(res.headers.get('location'), window.location.href).toString();
-			return res.text();
+
+			return res.text()
+				.then((answer) => onRemoteAnswer(answer));
 		})
-		.then((answer) => onRemoteAnswer(answer))
 		.catch((err) => {
 			onError(err.toString(), true);
 		});

internal/servers/webrtc/read_index.html

@@ -426,13 +426,17 @@
 				break;
 			case 404:
 				throw new Error('stream not found');
+			case 400:
+				return res.json().then((e) => { throw new Error(e.error); });
 			default:
 				throw new Error(`bad status code ${res.status}`);
 			}
+
 			sessionUrl = new URL(res.headers.get('location'), window.location.href).toString();
-			return res.text();
+
+			return res.text()
+				.then((sdp) => onRemoteAnswer(sdp));
 		})
-		.then((sdp) => onRemoteAnswer(sdp))
 		.catch((err) => {
 			onError(err.toString());
 		});