Multiplayer: Send an error message when connecting to a full room

src/citra_qt/multiplayer/message.cpp

@@ -22,6 +22,8 @@ const ConnectionError UNABLE_TO_CONNECT(
     QT_TR_NOOP("Unable to connect to the host. Verify that the connection settings are correct. If "
                "you still cannot connect, contact the room host and verify that the host is "
                "properly configured with the external port forwarded."));
+const ConnectionError ROOM_IS_FULL(
+    QT_TR_NOOP("Unable to connect to the room because it is already full."));
 const ConnectionError COULD_NOT_CREATE_ROOM(
     QT_TR_NOOP("Creating a room failed. Please retry. Restarting Citra might be necessary."));
 const ConnectionError HOST_BANNED(

src/citra_qt/multiplayer/message.h

@@ -27,6 +27,7 @@ extern const ConnectionError IP_ADDRESS_NOT_VALID;
 extern const ConnectionError PORT_NOT_VALID;
 extern const ConnectionError NO_INTERNET;
 extern const ConnectionError UNABLE_TO_CONNECT;
+extern const ConnectionError ROOM_IS_FULL;
 extern const ConnectionError COULD_NOT_CREATE_ROOM;
 extern const ConnectionError HOST_BANNED;
 extern const ConnectionError WRONG_VERSION;

src/citra_qt/multiplayer/state.cpp

@@ -102,6 +102,9 @@ void MultiplayerState::OnNetworkStateChanged(const Network::RoomMember::State& s
     case Network::RoomMember::State::MacCollision:
         NetworkMessage::ShowError(NetworkMessage::MAC_COLLISION);
         break;
+    case Network::RoomMember::State::RoomIsFull:
+        NetworkMessage::ShowError(NetworkMessage::ROOM_IS_FULL);
+        break;
     case Network::RoomMember::State::WrongPassword:
         NetworkMessage::ShowError(NetworkMessage::WRONG_PASSWORD);
         break;

src/network/room.cpp

@@ -68,6 +68,11 @@ public:
      */
     bool IsValidMacAddress(const MacAddress& address) const;
 
+    /**
+     * Sends a ID_ROOM_IS_FULL message telling the client that the room is full.
+     */
+    void SendRoomIsFull(ENetPeer* client);
+
     /**
      * Sends a ID_ROOM_NAME_COLLISION message telling the client that the name is invalid.
      */
@@ -193,6 +198,13 @@ void Room::RoomImpl::StartLoop() {
 }
 
 void Room::RoomImpl::HandleJoinRequest(const ENetEvent* event) {
+    {
+        std::lock_guard<std::mutex> lock(member_mutex);
+        if (members.size() >= room_information.member_slots) {
+            SendRoomIsFull(event->peer);
+            return;
+        }
+    }
     Packet packet;
     packet.Append(event->packet->data, event->packet->dataLength);
     packet.IgnoreBytes(sizeof(u8)); // Ignore the message type
@@ -295,6 +307,16 @@ void Room::RoomImpl::SendWrongPassword(ENetPeer* client) {
     enet_host_flush(server);
 }
 
+void Room::RoomImpl::SendRoomIsFull(ENetPeer* client) {
+    Packet packet;
+    packet << static_cast<u8>(IdRoomIsFull);
+
+    ENetPacket* enet_packet =
+        enet_packet_create(packet.GetData(), packet.GetDataSize(), ENET_PACKET_FLAG_RELIABLE);
+    enet_peer_send(client, 0, enet_packet);
+    enet_host_flush(server);
+}
+
 void Room::RoomImpl::SendVersionMismatch(ENetPeer* client) {
     Packet packet;
     packet << static_cast<u8>(IdVersionMismatch);
@@ -527,7 +549,9 @@ bool Room::Create(const std::string& name, const std::string& server_address, u1
     }
     address.port = server_port;
 
-    room_impl->server = enet_host_create(&address, max_connections, NumChannels, 0, 0);
+    // In order to send the room is full message to the connecting client, we need to leave one slot
+    // open so enet won't reject the incoming connection without telling us
+    room_impl->server = enet_host_create(&address, max_connections + 1, NumChannels, 0, 0);
     if (!room_impl->server) {
         return false;
     }

src/network/room.h

@@ -57,7 +57,8 @@ enum RoomMessageTypes : u8 {
     IdMacCollision,
     IdVersionMismatch,
     IdWrongPassword,
-    IdCloseRoom
+    IdCloseRoom,
+    IdRoomIsFull,
 };
 
 /// This is what a server [person creating a server] would use.

src/network/room_member.cpp

@@ -154,6 +154,9 @@ void RoomMember::RoomMemberImpl::MemberLoop() {
                     HandleJoinPacket(&event); // Get the MAC Address for the client
                     SetState(State::Joined);
                     break;
+                case IdRoomIsFull:
+                    SetState(State::RoomIsFull);
+                    break;
                 case IdNameCollision:
                     SetState(State::NameCollision);
                     break;

src/network/room_member.h

@@ -58,7 +58,8 @@ public:
         MacCollision,    ///< Somebody is already using that mac-address
         WrongVersion,    ///< The room version is not the same as for this RoomMember
         WrongPassword,   ///< The password doesn't match the one from the Room
-        CouldNotConnect ///< The room is not responding to a connection attempt
+        CouldNotConnect, ///< The room is not responding to a connection attempt
+        RoomIsFull       ///< Room is already at the maximum number of players
     };
 
     struct MemberInformation {