Referring to aCis project,
I noticed an issue that if you open a public server from your PC, other players can join but you can't join from the machine that you are running the server (as localhost).
Here is the quick fix about that issue,
@@ -22,10 +22,13 @@
_lastServer = client.getLastServer();
+ String clientIp = client.getConnection().getInetAddress().getHostAdd