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| -rw-r--r-- | step-05/README.md | 64 | ||||
| -rw-r--r-- | step-05/echo_client.erl | 6 | ||||
| -rw-r--r-- | step-05/echo_server.erl | 1 |
3 files changed, 66 insertions, 5 deletions
diff --git a/step-05/README.md b/step-05/README.md new file mode 100644 index 0000000..bc5f6ed --- /dev/null +++ b/step-05/README.md @@ -0,0 +1,64 @@ +*This is an alternative to `tut17`.* + +This example is an *echo server* to which you can send a `ping` message, and you will get a `pong` message in return. + +In this example session we start two Erlang nodes (doesn't have to be on the same machine), one named `es` for "echo +server" and another one named `node2`. + +Start and compile/load the code on both nodes: + +``` +$ erl -sname es +(es@biwia)1> c(echo_server). +``` + +``` +$ erl -sname node2 +(node2@biwia)1> c(echo_server). +``` + +Start the server: + +``` +(es@biwia)2> echo_server:start(). +Starting server, pid=<0.95.0> +true +(es@biwia)3> +``` + +The server uses `spawn/3` to run in the background. With the PID that `spawn` returns, it registers an `echo` name +that the client will use. We can look at this process with `regs()`: + +``` +(es@biwia)3> regs(). + +** Registered procs on node es@biwia ** +Name Pid Initial Call Reds Msgs +application_controlle <0.44.0> erlang:apply/2 784 0 +auth <0.60.0> auth:init/1 784 0 +code_server <0.50.0> erlang:apply/2 129042 0 +echo <0.95.0> echo_server:loop/1 5 0 +... +``` + +On the client side we can now send a ping message with `echo_client:send_ping(es@biwia)`. The `es@biwia` atom names +the *node* on the specific *host*. A host can run many nodes so the node name needs to be included. + +``` +(node2@biwia)2> echo_client:send_ping(es@biwia). +Sending echo to es@biwia, self=<0.88.0> +got pong from <14715.95.0> +ok +``` + +On the server you will notice this output: + +``` +(es@biwia)4> +<0.95.0>: Got ping req from: <14771.88.0> +(es@biwia)4> +``` + +Both the server and client uses `self/0` to find their own PID and you see that the server has the PID `0.95.0` and the +client has `0.85.0`. When the server receives the message the client pid is slightly different: `14771.88.0`, and the +same for the client's reply from the server. diff --git a/step-05/echo_client.erl b/step-05/echo_client.erl index 92785be..25ddffe 100644 --- a/step-05/echo_client.erl +++ b/step-05/echo_client.erl @@ -3,12 +3,10 @@ -export([send_ping/1]). send_ping(Echo_Node) -> - io:format("Sending echo to ~s~n", [Echo_Node]), - io:format("self=~p~n", [self()]), + io:format("Sending echo to ~s, self=~p~n", [Echo_Node, 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"). + end. diff --git a/step-05/echo_server.erl b/step-05/echo_server.erl index 3f531e5..2dcc425 100644 --- a/step-05/echo_server.erl +++ b/step-05/echo_server.erl @@ -18,5 +18,4 @@ loop(N) -> 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). |