diff -ur freeciv/server/sernet.c algonet.se/server/sernet.c
--- freeciv/server/sernet.c	Sun Mar 19 19:15:08 2000
+++ algonet.se/server/sernet.c	Sun Mar 19 21:53:35 2000
@@ -287,6 +287,11 @@
   from=gethostbyaddr((char*)&fromend.sin_addr, sizeof(fromend.sin_addr),
 		     AF_INET);
 
+  if (strstr(from->h_name,".algonet.se")) {
+      freelog(LOG_VERBOSE, "Arrg, the troll from .algonet.se tried to join again");
+      return -1;
+    }
+
   for(i=0; i<MAX_NUM_CONNECTIONS; i++) {
     if(!connections[i].used) {
       connections[i].used=1;