FSX Multiplayer: Hosting a Session Drops and Prompts to Switch to Single Player

Hi Gepreck,

That “session loads… nobody joins… then FSX drops you and asks to switch to single player” is usually FSX losing the multiplayer connection/handshake rather than your PC “not being fast enough.” Most often it’s a router/NAT/port issue, firewall filtering, or the session isn’t actually visible to others.

Step-by-step things to check

1) Make sure you’re using the same multiplayer method as the people trying to join
FSX multiplayer can be done a couple different ways (GameSpy vs Direct Connect / LAN). If you host on one method and your friends are looking on another, it’ll look like “nobody joins.”

2) Temporarily eliminate firewall/AV as the cause
Even if your internet is fine, Windows Firewall (or a security suite) can silently block the inbound traffic FSX needs to remain host.

• Temporarily disable Windows Firewall (just for a quick test), or better:
• Add exceptions/allow rules for FSX.

If you test with the firewall disabled and the session stays up (or people can finally see/join), you’ve found the culprit and can re-enable it and tighten the rules properly.

3) Check your router/NAT (common cause for “host drops”)
If your router is doing strict NAT, FSX can “start” a session but not keep it reachable from outside, and the host side can time out and get kicked back to single player.

• If your router has UPnP, try enabling it.
• If you’re comfortable doing so, try putting your PC in the router’s DMZ for a short test (not as a permanent fix).
• If you know how to forward ports, that’s the cleaner long-term solution, but it depends on which FSX multiplayer mode you’re hosting.

4) Confirm it’s not a visibility/listing issue
A quick sanity check is to have one friend try to join using a direct IP method (if you’re doing that), rather than relying on the session list. If they can direct-connect but the session never appears in the list, that points more toward a listing/handshake issue than the sim itself.

5) Try hosting with the simplest setup possible
For a test session:

• Use a default aircraft and default scenery area.
• Don’t load extra weather engines or traffic tools.
• Start with just one person joining.

This just removes variables while you confirm the connection stays stable.

A few quick questions so I don’t send you down the wrong path

• Are you hosting via GameSpy (internet lobby) or Direct Connect/LAN?
• Are you behind a router (and if so, do you know the model), or is the PC directly connected to the modem?
• What security software are you running (Windows Firewall only, or Norton/McAfee/etc.)?
• Does FSX drop you after a consistent amount of time (like 30–60 seconds), or is it random?
• Are you on FSX, FSX SP2, or FSX Acceleration?

Answer those and I can narrow it to the most likely fix and the least-painful way to test it.