Handle BadMsgNotification 32/33 by renewing session

FAQ.md

@@ -32,9 +32,9 @@ This might require adding a reference *(and `using`)* to the Microsoft.VisualBas
 
 #### 4. I get the error `CHAT_ID_INVALID` or `CHANNEL_INVALID`
 
-First, you should distinguish between Chat, Channel and Group/Supergroup: See Terminology in [ReadMe](README.md#Terminology-in-Telegram-Client-API)  
+First, you should distinguish between Chat, Channel and Group/Supergroup: See Terminology in [ReadMe](README.md#Terminology-in-Telegram-Client-API).  
-Most chat groups are in fact not a simple `Chat` but rather a (super)group (= a `Channel` without the `broadcast` flag)  
+Common chat groups are usually not a simple `Chat` but rather a supergroup: a `Channel` without the `broadcast` flag  
-Some TL methods only applies to simple Chat, and some only applies to Channels.
+Some TL methods only applies to simple `Chat`, and some only applies to `Channel`.
 
 A simple `Chat` can be queried using their `chat_id` only.  
 But a `Channel` must be queried using an `InputChannel` or `InputPeerChannel` object that specifies the `channel_id` as well as an `access_hash` that proves you are allowed to access it.

README.md

@@ -106,9 +106,9 @@ await client.SendMessageAsync(target, "Hello, World");
 # Terminology in Telegram Client API
 
 In the API, Telegram uses some terms/classnames that can be confusing as they differ from the terms shown to end-users:
-- `Channel` : A (large) chat group *(sometimes called supergroup)* or a broadcast channel (the `broadcast` flag differenciate those)
+- `Channel` : A (large or public) chat group *(sometimes called supergroup)* or a broadcast channel (the `broadcast` flag differenciate those)
-- `Chat` : A private simple chat group with few people (it may be migrated to a supergroup/channel when it doesn't fit anymore)
+- `Chat` : A private simple chat group with less than 200 members (it may be migrated to a supergroup `Channel` with a new ID when it gets bigger or public, in which case the old `Chat` will still exist but be `deactivated`)
-- Chats : In plural, it means either `Chat` or `Channel`
+- chats : In plural or general meaning, it means either `Chat` or `Channel`
 - `Peer` : Either a `Chat`, `Channel` or a private chat with a `User`
 - Dialog : The current status of a chat with a `Peer` *(draft, last message, unread count, pinned...)*
 - DC (DataCenter) : There are a few datacenters depending on where in the world the user (or an uploaded media file) is from.

src/Client.cs

@@ -837,19 +837,6 @@ namespace WTelegram
 					if (msgCopy?.orig_message?.body != null)
 						await HandleMessageAsync(msgCopy.orig_message.body);
 					break;
-				case BadServerSalt badServerSalt:
-					_dcSession.Salt = badServerSalt.new_server_salt;
-					if (badServerSalt.bad_msg_id == _dcSession.LastSentMsgId)
-					{
-						var newMsgId = await SendAsync(_lastSentMsg, true);
-						lock (_pendingRequests)
-							if (_pendingRequests.TryGetValue(badServerSalt.bad_msg_id, out var t))
-							{
-								_pendingRequests.Remove(badServerSalt.bad_msg_id);
-								_pendingRequests[newMsgId] = t;
-							}
-					}
-					break;
 				case TL.Methods.Ping ping:
 					_ = SendAsync(new Pong { msg_id = _lastRecvMsgId, ping_id = ping.ping_id }, false);
 					break;
@@ -864,17 +851,48 @@ namespace WTelegram
 				case MsgsAck msgsAck:
 					break; // we don't do anything with these, for now
 				case BadMsgNotification badMsgNotification:
-					{
+					await _sendSemaphore.WaitAsync();
+					bool retryLast = badMsgNotification.bad_msg_id == _dcSession.LastSentMsgId;
+					var lastSentMsg = _lastSentMsg;
+					_sendSemaphore.Release();
 					Helpers.Log(4, $"BadMsgNotification {badMsgNotification.error_code} for msg #{(short)badMsgNotification.bad_msg_id.GetHashCode():X4}");
-						var tcs = PullPendingRequest(badMsgNotification.bad_msg_id).tcs;
+					switch (badMsgNotification.error_code)
-						if (tcs != null)
+					{
+						case 32: // msg_seqno too low (the server has already received a message with a lower msg_id but with either a higher or an equal and odd seqno)
+						case 33: // msg_seqno too high (similarly, there is a message with a higher msg_id but with either a lower or an equal and odd seqno)
+							if (_dcSession.Seqno <= 1)
+								retryLast = false;
+							else
+							{
+								Reset(false, false);
+								_dcSession.Renew();
+								await ConnectAsync();
+							}
+							break;
+						case 48: // incorrect server salt (in this case, the bad_server_salt response is received with the correct salt, and the message is to be re-sent with it)
+							_dcSession.Salt = ((BadServerSalt)badMsgNotification).new_server_salt;
+							break;
+						default:
+							retryLast = false;
+							break;
+					}
+					if (retryLast)
+					{
+						var newMsgId = await SendAsync(lastSentMsg, true);
+						lock (_pendingRequests)
+							if (_pendingRequests.TryGetValue(badMsgNotification.bad_msg_id, out var t))
+							{
+								_pendingRequests.Remove(badMsgNotification.bad_msg_id);
+								_pendingRequests[newMsgId] = t;
+							}
+					}
+					else if (PullPendingRequest(badMsgNotification.bad_msg_id).tcs is TaskCompletionSource<object> tcs)
 					{
 						if (_bareRequest == badMsgNotification.bad_msg_id) _bareRequest = 0;
 						tcs.SetException(new ApplicationException($"BadMsgNotification {badMsgNotification.error_code}"));
 					}
 					else
 						OnUpdate(obj);
-					}
 					break;
 				default:
 					if (_bareRequest != 0)

src/Helpers.cs

@@ -12,7 +12,7 @@ namespace WTelegram
 		public static Action<int, string> Log { get; set; } = DefaultLogger;
 
 		/// <summary>For serializing indented Json with fields included</summary>
-		public static readonly JsonSerializerOptions JsonOptions = new() { IncludeFields = true, WriteIndented = true };
+		public static readonly JsonSerializerOptions JsonOptions = new() { IncludeFields = true, WriteIndented = true, IgnoreReadOnlyProperties = true };
 
 		public static V GetOrCreate<K, V>(this Dictionary<K, V> dictionary, K key) where V : new()
 			=> dictionary.TryGetValue(key, out V value) ? value : dictionary[key] = new V();

src/Session.cs

@@ -33,6 +33,7 @@ namespace WTelegram
 			internal Client Client;
 			internal int DcID => DataCenter?.id ?? 0;
 			internal IPEndPoint EndPoint => DataCenter == null ? null : new(IPAddress.Parse(DataCenter.ip_address), DataCenter.port);
+			internal void Renew() { Helpers.Log(3, $"Renewing session on DC {DcID}..."); Id = Helpers.RandomLong(); Seqno = 0; LastSentMsgId = 0; }
 		}
 
 		public DateTime SessionStart => _sessionStart;