🎮 Game Error Codes What it means & how to fix it

Sons of the Forest Co-op Won't Connect? Here's the Fix

If Sons of the Forest multiplayer 'fails to join' or friends never see your game, it's nearly always a version mismatch, a broken Steam/Epic Online Services link, or a mod on one side only. Fastest fix in 2026: make sure everyone is on the exact same game build with mods disabled, then have the host invite through the Steam overlay rather than the in-game list.

Sons of the Forest dedicated server — exact ports & config

Game port (UDP)
8766
Query port (UDP)
27016
BlobSync port (TCP)
9700
Config file
dedicatedserver.cfg (AppData\LocalLow\Endnight\SonsOfTheForestDS)
Common cause of stuck join
9700 is TCP (not UDP) and is easy to miss — without it clients hang on "joining world"

Last verified: September 2026

Error codes

Failed to join / stuck on joining The client connected to Steam but never entered the host's session

Cause: Version mismatch between host and client, or a corrupted Easy Anti-Cheat / EOS handshake.

Fix:
  1. Confirm every player is on the identical Sons of the Forest build — opt out of any beta branch so versions match.
  2. Host invites via the Steam friends overlay (Shift+Tab) instead of the in-game multiplayer list.
  3. Repair Easy Anti-Cheat from the game folder, then reboot.
  4. Verify integrity of game files in Steam on both host and client.
Friends can't see or join my game The session is created but never becomes visible/joinable to invitees

Cause: Privacy/friends settings, NAT/port issues, or mods loaded on only one machine.

Fix:
  1. Set the game to Friends Only and check your Steam profile isn't set to private (game details must be visible).
  2. Disable ALL mods on every player — a single mismatched mod silently blocks joins.
  3. If using a dedicated setup, forward UDP/TCP 8766 and 27015-27016 to the host.
  4. Restart Steam on both ends to refresh the friends/session list.

Fixes that work for most Sons of the Forest errors

  1. Everyone on the exact same build — opt out of beta branches so versions match.
  2. Host invites through the Steam overlay (Shift+Tab > friend > Invite), not the in-game list.
  3. Disable every mod on all players; re-enable one at a time only after co-op works.
  4. Repair Easy Anti-Cheat from the install folder and reboot.
  5. Verify integrity of game files in Steam on host and client.
  6. For a dedicated server, forward UDP/TCP 8766 and 27015-27016 to the host machine.

FAQ

Why can't my friend join my Sons of the Forest game?

Most often a version mismatch or a mod on one side. Match builds (opt out of betas), disable all mods, and invite via the Steam overlay.

Does Sons of the Forest need port forwarding for co-op?

Normal Steam invite co-op does not. Only a self-hosted dedicated server needs UDP/TCP 8766 and 27015-27016 forwarded.

Multiplayer worked yesterday and broke today — why?

A game update likely shifted your build. Make sure all players updated and are off any beta branch, then retry.

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