Re: systemd-activation: it's a mess for beginners

[Reindl Harald <h.reindl@xxxxxxxxxxxxx>]

Am 20.03.19 um 20:52 schrieb Mantas Mikulėnas:
> On Wed, Mar 20, 2019 at 9:46 PM Reindl Harald <h.reindl@xxxxxxxxxxxxx> wrote:
>>
>> http://0pointer.de/blog/projects/socket-activation.html
>>
>> ---------------------------------------------
>>
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <unistd.h>
>> #include <arpa/inet.h>
>> #include <netinet/in.h>
>> #include <stdio.h>
>> #include <sys/types.h>
>> #include <sys/socket.h>
>> #include <unistd.h>
>> #include <string.h>
>> #include <stdlib.h>
>> #include </usr/include/systemd/sd-daemon.h>
>>
>> int fd;
>>
>> if(sd_listen_fds(0) != 1)
>> {
>>  fprintf(stderr, "No or too many file descriptors received.\n");
>>  exit(1);
>> }
>>
>> fd = SD_LISTEN_FDS_START + 0;
>>
>> ---------------------------------------------
>>
>> demo-udp.c:16:1: error: expected identifier or '(' before 'if'
>>  if(sd_listen_fds(0) != 1)
>>  ^~
>> demo-udp.c:22:1: warning: data definition has no type or storage class
>>  fd = SD_LISTEN_FDS_START + 0;
>>  ^~
>> demo-udp.c:22:1: warning: type defaults to 'int' in declaration of 'fd'
>> [-Wimplicit-int]
>>
>> ---------------------------------------------
> 
> I think you got the wrong mailing list; the requirement to put the
> code inside a main() function is a basic feature of C syntax and is
> not part of systemd

look again at the already working, systemd independent service

the code snippet is from here:
http://0pointer.de/blog/projects/socket-activation.html

i just want a binary fired up by systemd socket-activation on whatever
port receibe UDP connections and the port shouldn't matter because PID1
is listenining and handover the socket

not more, not less

-------- Weitergeleitete Nachricht --------
Betreff: Re:  udp socket-activation "fake-service"
Datum: Mon, 18 Mar 2019 10:54:34 +0100
Von: Lennart Poettering <lennart@xxxxxxxxxxxxxx>

I am not fully grokking what you are trying to do, but to recv UDP
dgrams you'd have to write a tiny program that calls recvfrom() (or a
similar syscall) on the sockets passed, and then replies to it with
sendto() (or a similar syscall), using the address of the source
(i.e. the struct sockaddr recvfrom() returns) to respond to the dgram.

You can easily hack that up in C or some scripting language. I am not
aware of a ready-made tool that can do that for you, in particularly
of non that is capable of doing that for more than one listening UDP
socket at a time.
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