2018-07-07 00:17:09: ACTION[Server]: Server: A mismatched client tried to connect from xxx.xx.xx.xxx
2018-07-07 00:33:23: ACTION[Server]: someuser [yyy.yyy.yy.yyy] joins game.
2018-07-07 00:33:23: ACTION[Server]: someuser joins game. List of players: someuser
2018-07-07 00:33:24: ACTION[Server]: someuser leaves game. List of players:
The server (self build 0.4 stable from github) crashed with only 'segmentation fault' at the terminal. Unlike crashing because of mods bugs that can be traced back to it's source using debug.txt, the crash leaves no information. I have tried to connect using official clients in ubuntu (self build and official repo), windows (official download) and android (playstore) successfully without crashing the server. I also have tried connecting from internet though very slow and laggy but no problem. Does it mean someone was using unaccepted client?
My server is ubuntu 16.04 server intended for local play due to heavy media and limited bandwidth but someone from outside can connect because I open the port but that's ok actually if they enjoy the game. Now I use password to avoid someone crashing the server.
If no crash dump is available, then you could run minetest/minetestserver in gdb and get a backtrace using "bt", which then provides more helpful information about the crash. Additional information is provided when the crash was caught in a development build, on the cost of a larger binary and slower execution (server lags more).
Many other crashes have been reported on the master branch here. Since you're on 0.4.17.1 (confirm with "minetest --version"), it would be helpful if you could provide the crash dump in a new issue if it's not contained in #7272.
I don't know how to reproduce myself, I only use clean unmodded client from git and repo. Currently hosted at krambtest.ddns.net port 40000 if somebody like to visit. If it is listed at server list as Alone in Wild Land then it is online, media heavy so please be patient.