Quick answer
What to do first
Identify the failed stage first. If the host terminates, inspect the host's startup log. If the server is running but unreachable, confirm address, network mode and the owner's connection settings. If loading begins then rejects you, compare builds, mods and the exact error. Back up before changing world data; do not disable security globally or delete your save as a first fix.
Check your game conditions
- Current Stable
- 42.20.4 Stable
- Play mode
- Multiplayer (Host or dedicated server)
- Vanilla / Mods
- Vanilla baseline; mods may replace rules
- Sandbox / server settings
- Steam/network mode, server address, permissions and active mod set must match.
At what stage does joining fail?
Host never finishes starting
- Possible cause
- Startup/configuration/content failure
- Check
- First meaningful host error and whether the process remains alive
- Next action
- The owner fixes startup before clients retry.
Server runs but no one can reach it
- Possible cause
- Address, port or network-mode mismatch
- Check
- The owner's actual join details and configured mode
- Next action
- Use matching details; have the owner verify only the necessary network permissions.
Some players can join, you cannot
- Possible cause
- Client build/content or access differs
- Check
- Exact build, mod versions and account permissions
- Next action
- Match the working configuration without copying another player's private credentials.
Connection begins then loading fails
- Possible cause
- Content mismatch, rejected files or world issue
- Check
- Exact error and which side reports it
- Next action
- Investigate that message; do not disable integrity checks to hide it.
Only the modded profile fails
- Possible cause
- Third-party dependency or compatibility problem
- Check
- Separate vanilla test profile and author requirements
- Next action
- Preserve the real world, then isolate the added content safely.
Collect the smallest useful comparison
Ask whether the owner can start the server and whether any other player can join. Those two answers sharply reduce the possibilities. A server that is not running cannot be fixed by changing a client's graphics settings.
Compare the exact build number, not just the words Build 42. Then check Steam/network mode and the required mod set. If versions changed recently, the owner and clients should finish the agreed update before trying the same connection again.
Use logs without sacrificing the save
Keep the exact error message and the first relevant startup or connection error. Redact IP addresses, passwords, tokens and other private details before sharing a log publicly. Use the official support route or the relevant mod author when the problem exceeds the documented checks.
A clean test means a separate temporary world or profile, not deleting your established save. Do not turn off the firewall, antivirus or server validation globally. Where a network permission is actually missing, the server owner should use a narrow rule appropriate to the configured server.
Version notes & limits
Older P2P discussions describe specific versions and machines. This guide uses current Stable context but does not treat one historical workaround as a permanent B42 solution.
Safe, stage-based connection diagnosis. No universal P2P fix, router-specific installation guide, port blanket or instruction to bypass server checks.
Last verified means the linked documentation was reviewed, not that this guide was tested in-game. PZwiki is maintained by community contributors.
Version & sources
Sources & what may change
- Applies to
- 42.20.4 Stable; Multiplayer (Host or dedicated server); Vanilla baseline; mods may replace rules
- Last verified
- 2026-09-04
- When to check again
- A relevant Stable patch, changed world setting, mod update or correction to the cited instructions.