Multiplayer Connectivity Help

Before troubleshooting

• Joining is much easier than hosting, so first try joining a known-working host player to determine whether hosting is the issue.
• Use the same KeeperFX version on every computer.
• Allow KeeperFX through Windows Defender Firewall and other firewalls.
• Temporarily disable VPNs.
• Restart KeeperFX after changing network settings.

Quick diagnosis

Result	Check
You can join other lobbies	Original host's network
Nobody can join you	Firewall, UDP 5556, NAT, or router
You cannot join anyone	Firewall, VPN, DNS, or restricted network
LAN Direct Connect works, discovery fails	UDP 5557
LAN Direct Connect fails	Firewall or network isolation
No online lobbies appear	Matchmaking, DNS, network filtering, or version

Online games

KeeperFX uses a matchmaking master server to introduce players, then attempts a direct UDP connection over IPv4 or IPv6. This online lobby discovery requires a connection to matchmaking.keeperfx.workers.dev and stun.l.google.com. Firewalls, DNS filters, routers, and restricted networks can block these services or UDP hole punching.

If you cannot join:

1. Try a known-working host.
2. If that works, troubleshoot the original host.
3. Otherwise, check your firewall and try without VPN or security software.
4. If no lobbies appear, check DNS or network filtering.

If others cannot join you, KeeperFX hosts on UDP port 5556. It tries NAT-PMP, UPnP, IPv6, and UDP hole punching automatically. Check the following:

1. Allow KeeperFX through the host's firewall.
2. Enable NAT-PMP or UPnP in the router, for automatic port forwarding.
3. Visit test-ipv6.com to check whether your computer has working IPv6 internet access. IPv6 may allow hosting without IPv4 port forwarding, but the router and PC firewalls must still allow KeeperFX.

If hosting still does not work, the host should open up their router settings and manually port-forward UDP 5556 in the IPv4 section.

Port forwarding may fail with:

• CGNAT: Ask your provider for a public IPv4 address.
• Double NAT: Forward through both routers, or use bridge or access-point mode.

For Direct Connect over the internet, enter the host's public IP address or hostname. Port 5556 is used by default, and the host may need UDP 5556 forwarded.

Some networks simply cannot establish peer-to-peer UDP connections.

LAN games

Use the LAN Lobby when everyone is on the same network. UDP 5557 handles lobby discovery and UDP 5556 the game.

If the lobby does not appear, open Direct Connect from the launcher menu beside Play and enter the host's local IPv4 address, such as 192.168.1.50. Check both firewalls and disable guest-network, AP-isolation, or client-isolation settings.

LAN games need no internet port forwarding. Do not use the router's public IP address.