All players within a single ranking game need different ip addresses.

src/net/common/servergame.cpp

@@ -581,6 +581,12 @@ ServerGame::IsPlayerConnected(unsigned playerId) const
 	return GetSessionManager().IsPlayerConnected(playerId);
 }
 
+bool
+ServerGame::IsClientAddressConnected(const std::string &clientAddress) const
+{
+	return GetSessionManager().IsClientAddressConnected(clientAddress);
+}
+
 bool
 ServerGame::IsRunning() const
 {

src/net/common/serverlobbythread.cpp

@@ -1395,6 +1395,11 @@ ServerLobbyThread::HandleNetPacketJoinGame(SessionWrapper session, const std::st
 		{
 			SendJoinGameFailed(session.sessionData, joinGame.gameId, NTF_NET_JOIN_INVALID_PASSWORD);
 		}
+		else if (tmpData.gameType == GAME_TYPE_RANKING
+			&& game.IsClientAddressConnected(session.sessionData->GetClientAddr()))
+		{
+			SendJoinGameFailed(session.sessionData, joinGame.gameId, NTF_NET_JOIN_GAME_FULL);
+		}
 		else
 		{
 			MoveSessionToGame(game, session);

src/net/common/sessionmanager.cpp

@@ -218,6 +218,27 @@ SessionManager::IsPlayerConnected(unsigned uniqueId) const
 	return retVal;
 }
 
+bool
+SessionManager::IsClientAddressConnected(const std::string &clientAddress) const
+{
+	bool retVal = false;
+	boost::recursive_mutex::scoped_lock lock(m_sessionMapMutex);
+
+	SessionMap::const_iterator i = m_sessionMap.begin();
+	SessionMap::const_iterator end = m_sessionMap.end();
+
+	while (i != end)
+	{
+		if ((*i).second.sessionData->GetClientAddr() == clientAddress)
+		{
+			retVal = true;
+			break;
+		}
+		++i;
+	}
+	return retVal;
+}
+
 void
 SessionManager::ForEach(boost::function<void (SessionWrapper)> func)
 {