How to get a SteamID?

[Atmosaero]

How can I get the SteamID of users who have joined my lobby?

[Josh]

https://www.ultraengine.com/learn/Steamworks_GetLobbyMembers

[Josh]

Actually, there is some more advanced functionality available. You can see an event is emitted with ID EVENT_LOBBYUSERDISCONNECT and the event source is a LobbyEventInfo object. You have to cast like this:
auto info = event.source->As<LobbyEventInfo>()

And that has the lobby and user IDs.

	void CallbackManager::OnLobbyChatUpdate(LobbyChatUpdate_t* pCallback)
	{
		auto info = std::make_shared<LobbyEventInfo>();
		info->lobbyid = pCallback->m_ulSteamIDLobby;
		info->userid = pCallback->m_ulSteamIDUserChanged;
		if ((k_EChatMemberStateChangeEntered & pCallback->m_rgfChatMemberStateChange) != 0)
		{
			__queuedevents.push_back(Event(EVENT_LOBBYUSERJOIN, info));
			SteamNetworking()->AcceptP2PSessionWithUser(pCallback->m_ulSteamIDUserChanged);
		}
		if ((k_EChatMemberStateChangeLeft & pCallback->m_rgfChatMemberStateChange) != 0) __queuedevents.push_back(Event(EVENT_LOBBYUSERLEAVE, info));
		if ((k_EChatMemberStateChangeDisconnected & pCallback->m_rgfChatMemberStateChange) != 0) __queuedevents.push_back(Event(EVENT_LOBBYUSERDISCONNECT, info));
	}