From aa3c25288e44bcf082680308256f9390cba50bbc Mon Sep 17 00:00:00 2001
From: Trygve Laugstøl <trygvis@inamo.no>
Date: Fri, 23 Feb 2024 20:21:53 +0100
Subject: wip

---
 README.md               | 10 ++++++++++
 step-05/echo_client.erl | 14 ++++++++++++++
 step-05/echo_server.erl | 22 ++++++++++++++++++++++
 3 files changed, 46 insertions(+)
 create mode 100644 step-05/echo_client.erl
 create mode 100644 step-05/echo_server.erl

diff --git a/README.md b/README.md
index a3630cb..15c5ae2 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,16 @@ apt install rebar3      # depends on erlang
 
 # Resources
 
+* https://www.erlang.org/doc/
+* https://www.erlang.org/doc/reference_manual
 * https://learnyousomeerlang.com/
 * https://adoptingerlang.org
 * https://www.jetbrains.com/help/idea/erlang-start-project.html
+
+# Notes
+
+* All nodes in system: `net_adm:names()`.
+* Show all processes and registered names: `i()`.
+  * ... on all nodes `ni()`.
+* Show all registered processes: `regs()`.
+* 
\ No newline at end of file
diff --git a/step-05/echo_client.erl b/step-05/echo_client.erl
new file mode 100644
index 0000000..92785be
--- /dev/null
+++ b/step-05/echo_client.erl
@@ -0,0 +1,14 @@
+-module(echo_client).
+
+-export([send_ping/1]).
+
+send_ping(Echo_Node) ->
+  io:format("Sending echo to ~s~n", [Echo_Node]),
+  io:format("self=~p~n", [self()]),
+  {echo, Echo_Node} ! {ping, self()},
+  receive
+    {pong, Server} -> io:format("got pong from ~w~n", [Server]);
+    X -> io:format("Unexpected reply: ~w~n", [X])
+  after 1000 -> io:format("timeout~n")
+  end,
+  io:format("done~n").
diff --git a/step-05/echo_server.erl b/step-05/echo_server.erl
new file mode 100644
index 0000000..3f531e5
--- /dev/null
+++ b/step-05/echo_server.erl
@@ -0,0 +1,22 @@
+-module(echo_server).
+
+-export([start/0, loop/1]).
+
+loop(0) ->
+  io:format("ping finished~n", []);
+
+loop(N) ->
+  receive
+    {ping, Node} ->
+      io:format("~w: Got ping req from: ~w~n", [self(), Node]),
+      Node ! {pong, self()};
+    X ->
+      io:format("Unexpected message: ~w~n", [X])
+  end,
+  echo_server:loop(N - 1).
+
+start() ->
+  Pid = spawn(echo_server, loop, [10]),
+  io:format("Starting server, pid=~w~n", [Pid]),
+  io:format("Starting server, pid=~w~n", [Pid]),
+  register(echo, Pid).
-- 
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