[erlang-questions] about Erlang C Node monitor

Yu-Teh Shen <>
Tue Dec 15 02:35:38 CET 2009


Hi Matt,

Thanks a lot!

It help me a lot~

Shen, Yu-Teh

On Mon, Dec 14, 2009 at 4:48 PM, Matt Stancliff <>wrote:

> Yu-Teh,
>
>
> On Dec 13, 2009, at 11:36 PM, Yu-Teh Shen wrote:
>
>> But what I should do if I want to *monitor* the C node like all other
>> Erlang
>> node and make erlang *connects*, *net_adm:ping* works?
>>
>
> You can use erlang:monitor_node to monitor C nodes.
>
> Handling net_adm:ping in a C node takes a few steps.  Here is what I use:
>
> main processing loop:
> =====
>  ETERM *gen_call         = erl_format("~a", "$gen_call");
>
>  while (loop) {
>
>    got = erl_receive_msg(fd, buf, BUFSIZE, &emsg);
>    if (got == ERL_TICK) {
>      /* ignore */
>    } else if (got == ERL_ERROR) {
>      loop = 0;
>
>    }
>    else {
>      if (emsg.type == ERL_REG_SEND) {
>        msg = erl_element(1, emsg.msg);
>        if (erl_match(_something_i_want_, msg)) {
>          /* blah */
>        }
>        else if (erl_match(gen_call, msg)) {
>          process_gen_call(fd, emsg.from, emsg.msg);
>        }
>      }
>    }
>    erl_free_term(msg);
>    erl_free_term(emsg.msg);
>    erl_free_term(emsg.to);
>    erl_free_term(emsg.from);
>  }
>  erl_free_term(gen_call);
> =====
>
> Then, process_gen_call is:
> =====
> /* gen_call with is_auth is for handling net_adm:ping responses.
>   The incoming message looks like:
>   {'$gen_call', {<>, #Ref<2394.0.0>},
>     {is_auth, }}
>   You must respond with the reference (element 2 of tuple 2) and "yes"
> */
> static void process_gen_call(int fd, ETERM *from, ETERM *msg) {
>  ETERM *is_auth  = erl_format("~a", "is_auth");
>  ETERM *args = erl_element(3, msg);
>  ETERM *arg1 = erl_element(1, args);
>  if (erl_match(is_auth, arg1)) {
>    ETERM *fromp = erl_element(2, msg);
>    ETERM *resp = erl_format("{~w, yes}", erl_element(2, fromp));
>    erl_send(fd, from, resp);
>    erl_free_compound(resp);
>    erl_free_term(fromp);
>  }
>  erl_free_term(args);
>  erl_free_term(arg1);
>  erl_free_term(is_auth);
> }
> =====
>
>
> Hope that helps,
>
> -Matt
> --
> Matt Stancliff                    San Jose, CA
> AIM: seijimr              iPhone: 678-591-9337
> "The best way to predict the future is to invent it." --Alan Kay
>
>


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