Check if another player has the same serial

Client/mods/deathmatch/logic/CPacketHandler.cpp

@@ -572,6 +572,10 @@ void CPacketHandler::Packet_ServerDisconnected(NetBitStreamInterface& bitStream)
             strReason = _("Disconnected: Serial verification failed");
             strErrorCode = _E("CD44");
             break;
+        case ePlayerDisconnectType::SERIAL_DUPLICATE:
+            strReason = _("Disconnected: Serial already in use");
+            strErrorCode = _E("CD50");
+            break;
         case ePlayerDisconnectType::CONNECTION_DESYNC:
             strReason = _("Disconnected: Connection desync %s");
             strErrorCode = _E("CD45");

Client/mods/deathmatch/logic/CPacketHandler.h

@@ -38,6 +38,7 @@ class CPacketHandler
         ELEMENT_FAILURE,
         GENERAL_REFUSED,
         SERIAL_VERIFICATION,
+        SERIAL_DUPLICATE,
         CONNECTION_DESYNC,
         BAN,
         KICK,

Server/mods/deathmatch/logic/CGame.cpp

@@ -1798,6 +1798,19 @@ void CGame::Packet_PlayerJoinData(CPlayerJoinDataPacket& Packet)
             return;
         }
 
+        // Check if another player is using the same serial
+        CPlayer* playerExisting = m_pPlayerManager->GetBySerial(strSerial);
+
+        if (playerExisting)
+        {
+            // Tell the console
+            CLogger::LogPrintf("CONNECT: %s failed to connect (Serial already in use) (%s)\n", szNick, strIPAndSerial.c_str());
+
+            // Tell the player the problem
+            DisconnectPlayer(this, *pPlayer, CPlayerDisconnectedPacket::SERIAL_DUPLICATE);
+            return;
+        }
+
         // Check the nick is valid
         if (!CheckNickProvided(szNick))
         {

Server/mods/deathmatch/logic/CPlayerManager.cpp

@@ -138,6 +138,19 @@ CPlayer* CPlayerManager::Get(const char* szNick, bool bCaseSensitive)
     return NULL;
 }
 
+CPlayer* CPlayerManager::GetBySerial(const SString& serial) const noexcept
+{
+    for (auto& player : m_Players)
+    {
+        if (player->GetSerial() == serial)
+        {
+            return player;
+        }
+    }
+
+    return nullptr;
+}
+
 void CPlayerManager::DeleteAll()
 {
     // Delete all the items in the list

Server/mods/deathmatch/logic/CPlayerManager.h

@@ -40,6 +40,7 @@ class CPlayerManager
 
     CPlayer* Get(const NetServerPlayerID& PlayerSocket);
     CPlayer* Get(const char* szNick, bool bCaseSensitive = false);
+    CPlayer* GetBySerial(const SString& serial) const noexcept;
 
     std::list<CPlayer*>::const_iterator IterBegin() { return m_Players.begin(); };
     std::list<CPlayer*>::const_iterator IterEnd() { return m_Players.end(); };

Server/mods/deathmatch/logic/packets/CPlayerDisconnectedPacket.h

@@ -35,6 +35,7 @@ class CPlayerDisconnectedPacket final : public CPacket
         ELEMENT_FAILURE,
         GENERAL_REFUSED,
         SERIAL_VERIFICATION,
+        SERIAL_DUPLICATE,
         CONNECTION_DESYNC,
         BAN,
         KICK,