chat_server.erl

-module(chat_server).

-export([start/1]).

handle_socket(Router, Client) ->
    case gen_tcp:recv(Client, 0) of
        {ok, Data} ->
            case string:str(binary_to_list(Data), "!quit") of
                1 ->
                    Router ! {delete, Client},

                    gen_tcp:close(Client);
                _ ->
                    Router ! {msg, Client, Data}
            end,

            handle_socket(Router, Client);

        {error, closed} ->
            io:write("Client quit\r\n"),

            Router ! {delete, Client}
    end.

loop(Router, Server) ->
    {ok, Client} = gen_tcp:accept(Server),

    gen_tcp:send(Client, "You are now connected!\r\n"),

    Router ! {add, Client},

    spawn(fun() -> loop(Router, Server) end),

    handle_socket(Router, Client).

route_msg([], _Client, _Data) ->
    ok;

route_msg([H|T], Client, Data) when H == Client ->
    route_msg(T, Client, Data);

route_msg([H|T], Client, Data) ->
    Message = io_lib:format("~p: ~s", [Client, Data]),

    gen_tcp:send(H, Message),

    route_msg(T, Client, Data).

router(Clients) ->
    io:format("Clients:~n"),
    io:format("~p~n", [Clients]),

    receive
        {add, Client} ->
            io:format("Added client: ~p~n", [Client]),

            router(lists:append(Clients, [Client]));

        {delete, Client} ->
            io:format("Deleted client: ~p~n", [Client]),

            router(lists:delete(Client, Clients));

        {msg, Client, Data} ->
            io:format("Incoming ~p: ~s", [Client, Data]),

            route_msg(Clients, Client, Data),
            router(Clients)
    end.

start(Port) ->
    {ok, Server} = gen_tcp:listen(Port, [ binary,
                                                {packet, 0},
                                                {active, false},
                                                {reuseaddr, true} ]),

    Router = spawn(fun() -> router([]) end),

    loop(Router, Server).