--- a/src/rps.erl	Sun Mar 02 22:41:13 2014 +0900
+++ b/src/rps.erl	Mon Mar 03 15:09:55 2014 +0900
@@ -6,7 +6,7 @@
 -define(BOTS, [fool, copycat, gambler]).
 
 go() ->
-    register(nickserv, spawn_link(rps_nickserv, nickserv, [])),
+    rps_nickserv:start_link(),
     register(lobby, spawn_link(?MODULE, lobby, [])),
     register(counter, spawn_link(?MODULE, counter, [])),
     register(printer, spawn_link(?MODULE, printer, [])),

--- a/src/rps_bots.erl	Sun Mar 02 22:41:13 2014 +0900
+++ b/src/rps_bots.erl	Mon Mar 03 15:09:55 2014 +0900
@@ -3,7 +3,7 @@
 -export([fool/0, copycat/0, gambler/0]).
 
 fool() ->
-    nickserv ! {nick, self(), "fool"},
+    rps_nickserv:nick(self(), "fool"),
     lobby ! {join, self()},
     fool(joined).
 
@@ -25,7 +25,7 @@
     end.
 
 copycat() ->
-    nickserv ! {nick, self(), "copycat"},
+    rps_nickserv:nick(self(), "copycat"),
     lobby ! {join, self()},
     copycat(joined).
 
@@ -45,7 +45,7 @@
     end.
 
 gambler() ->
-    nickserv ! {nick, self(), "gambler"},
+    rps_nickserv:nick(self(), "gambler"),
     lobby ! {join, self()},
     gambler(joined).
 

--- a/src/rps_nickserv.erl	Sun Mar 02 22:41:13 2014 +0900
+++ b/src/rps_nickserv.erl	Mon Mar 03 15:09:55 2014 +0900
@@ -1,20 +1,31 @@
 -module(rps_nickserv).
--export([nickserv/0, whois/1]).
+-behaviour(gen_server).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
+-export([start_link/0, nick/2, whois/1]).
 
-nickserv() ->
-    nickserv(dict:new()).
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+init([]) ->
+    {ok, dict:new()}.
 
-nickserv(Nicknames) ->
-    receive
-        {nick, Who, Nickname} ->
-            nickserv(dict:store(Who, Nickname, Nicknames));
-        {whois, Pid, Who} ->
-            Pid ! {ok, dict:fetch(Who, Nicknames)},
-            nickserv(Nicknames)
-    end.
+handle_call({nick, Who, Nickname}, _From, Nicknames) ->
+    io:format("~w registered as ~s.~n", [Who, Nickname]),
+    {reply, ok, dict:store(Who, Nickname, Nicknames)};
+
+handle_call({whois, Who}, _From, Nicknames) ->
+    {reply, dict:fetch(Who, Nicknames), Nicknames}.
+
+handle_cast(_Msg, State) -> {noreply, State}.
+
+handle_info(_Msg, State) -> {noreply, State}.
+
+terminate(_Reason, _State) -> ok.
+
+code_change(_OldVersion, State, _Extra) -> {ok, State}.
+
+nick(Who, Nickname) ->
+    gen_server:call(?MODULE, {nick, Who, Nickname}).
 
 whois(Who) ->
-    nickserv ! {whois, self(), Who},
-    receive
-        {ok, Nickname} -> Nickname
-    end.
+    gen_server:call(?MODULE, {whois, Who}).