# Unable to Create / Join EOS Lobby (P2P) using custom implementation

[justAbhi77]

Hi,

Tldr: The official tutorial project works for me, but my minimal widget-based implementation (EosHandler) does not.

I’ve been struggling to get an EOS lobby / session system for peer-to-peer hosting and joining working, but I’ve hit a wall. I’ve tried multiple approaches, reviewed documentation, example projects, and even rewrote my handler several times, but I consistently get errors that prevent me from hosting or joining successfully.

What I’m Seeing

• When trying to create or join a lobby, I frequently get errors like:
  • "Player not being in session"
  • "Lobby session missing attribute from backend"

These errors are very cryptic and don’t really tell me what’s wrong.

What I Tried

• Implemented login, session search, lobby creation, and joining logic through the EOS OnlineSubsystem in Unreal (see attached EosHandler.h/.cpp) using the tutorial as reference.
• Verified that login succeeds before session creation.
• Attempted multiple variations of session settings (different keys, attributes, map strings, lobby/session names).
• Tried both listen server and dedicated-style setups.
• Double-checked that the OnlineSubsystemEOS is initialized and returning valid pointers.
• This makes me wonder if I’m missing some hidden requirement or setup step that the tutorial project includes.

Expected Behavior

• Be able to:
  1. Log in successfully.
  2. Create a lobby session for hosting.
  3. Find that session from another client.
  4. Join it without EOS throwing unclear errors.

Actual Behavior

• Logged in successfully.
• Lobby creation or join usually fails with either:
  • "player not in session"
  • "missing attribute from backend"
• No clear guidance in logs/docs about what attribute is missing or why EOS considers the player not in the session.

Additional Info

• Using Launcher Unreal Engine 5.3
• EOS Online Subsystem integrated
• Code reference: EosHandler.h / EosHandler.cpp (attached)

---

Request

Could someone clarify what typically causes these errors? Is there a required session attribute that must always be set when creating a lobby? Or is there something specific about how EOS expects login → create session → join flow to happen that I might be missing?

Any guidance, examples, or working snippets would be hugely appreciated.

Thanks!

Header file

EosHandler.h

Cpp file

EosHandler.cpp

Edit 1 : added files since github did not uploaded them.