Simpliest unix non-blocking "broadcast" socket

Question

I have non-regularly running program which outputs string, I need to send this output to some kind of socket which can be distributed out of docker container and which can be listened by multiple listeners or even none.

I know standard FIFO named pipe but it expects to have one listener and notifier connected until that moment it stays blocked.

Is there way to obtain this type socket with "standard" linux commands or daemons? I am looking for solution with smallest number of dependencies, easily maintained...

EDIT:

i've found socat can work in this way, but i am unable to share mesagess to all clients.

shell1$ socat pipe:/tmp/test-in unix-listen:/tmp/test-out,fork
shell2$ socat - UNIX-CONNECT:/tmp/test-out
shell3$ socat - UNIX-CONNECT:/tmp/test-out
shell4$ echo "test" > socat - UNIX-CONNECT:/tmp/test-in

(shell2) test

You should not be using UNIX domain sockets in a Docker environment. Make normal IP network connections. — Michael Hampton, Jan 10 '16 at 15:19
Because it's Docker, of course. Trying to share sockets between containers breaks what little security the model has, and ties your containers down so you can't move them. — Michael Hampton, Jan 10 '16 at 15:25
How it breaks security? Its not movable by a choice (it can be easily changed to IP socket though). — user2216697, Jan 10 '16 at 15:34

score 1 · Answer 1 · edited Apr 13 '17 at 12:37

Found solution at similar answer https://unix.stackexchange.com/questions/195880/socat-duplicate-stdin-to-each-connected-client. Socat seems can't work that way but ncat from nmap package does.

It works same for unix socket:

% mkfifo /tmp/messages-in
% exec 8<>/tmp/messages-in  # hold the fifo open
% ncat -l -U /tmp/messages-out -k --send-only < /tmp/messages-in

% echo "test" > /tmp/messages-in

% # every client connected to /tmp/messages-out will get "test" message

Simpliest unix non-blocking "broadcast" socket

1 Answers1