it begindth

x00-hello/hello_client.erl

@@ -0,0 +1,18 @@
+-module(hello_client).
+
+-export([main/0]).
+
+main() ->
+    {ok, Socket} = gen_tcp:connect("localhost", 6969, [binary, {packet, 0}]),
+    loop(Socket).
+
+loop(Socket) ->
+    ok = inet:setopts(Socket, [{active, once}]),
+    receive
+        {tcp, Socket, Bytes} ->
+            ok = io:format("< ~tp~n", [Bytes]),
+            loop(Socket);
+        {tcp_closed, Socket} ->
+            ok = io:format("connection terminated~n", []),
+            exit(normal)
+    end.

x00-hello/hello_server.erl

@@ -0,0 +1,14 @@
+-module(hello_server).
+
+-export([main/0]).
+
+main() ->
+    {ok, ListenSocket} = gen_tcp:listen(6969, [binary, {packet, 0}, {active, false}]),
+    %% blocks until client connects
+    {ok, Socket} = gen_tcp:accept(ListenSocket),
+    Msg = <<"hello, world">>,
+    ok = io:format("> ~tp~n", [Msg]),
+    ok = gen_tcp:send(Socket, Msg),
+    ok = gen_tcp:close(Socket),
+    ok = gen_tcp:close(ListenSocket),
+    ok.