Troubleshooting multiplayer

Dedicated server

Host has failed to respond

"A connection attempt failed because the connected party did not properly respond after a period of time, or established connect failed because connected host has failed to respond."
Problem: likely an error in the port forwarding
Solution: create permissions for both TCP and UDP protocols (separately). "TCP/UDP" is unlikely to work although logically it should.

If it worked before and not today, check the IP address again. It's possible that the IP address changed without the host knowing.

Host has actively refused

Problem: likely an overprotective firewall
Solution: create permissions for vintagestory

Lag / Host not responding

Troubleshooting_Guide#Multiplayer_lag_/_Host_not_responding_messages

Misc connection issues

Troubleshooting_Guide#Multiplayer_connection_issues

1kb downloaded

If it takes more than 30 seconds to download the first kilobyte, use the Cancel button and try again. The next attempt is usually normal-fast.