Re: multiple starts for a socket-based service [SOLVED]

[Ross Boylan <rossboylan@xxxxxxxxxxxxxxxxxx>]

Thank you, Mantas.  With your very detailed response I was able to get
something working.  I also added StandardInput=socket to the service
to give easy access to the command from the client.

Here's the current configuration:
# /etc/systemd/system/family.socket
[Unit]
Description=Socket to tickle to update family netboot config

[Install]
WantedBy=network-online.target

[Socket]
ListenStream=192.168.1.10:14987
# want to run a new job, aka service, for each connection.
Accept=Yes
BindToDevice=br0
# 2s is default
TriggerLimitIntervalSec=5s

# /etc/systemd/system/family@.service
# [Socket] Accept=yes requires a multi-instance service, hence @ in file name.
[Unit]
Description=Update kernel netboot info for family system

[Service]
# not Type=oneshot for  socket-activated
Type=simple
# next is the default.
RemainAfterExit=no
StandardInput=socket
ExecStart=sh -c "cat >> /root/washere"

# [Install] doesn't make sense for socket-activated services

There was one thing I wrote originally that I didn't mean:
>> in which the server
>> generates a new port, communicates it to the client, and it is this
>> second port that gets handed to the service?  Or is the expectation
>> that the client service will do that early on and close the original
>> port?
The last sentence should have read "service" not "client service".  I
had the server process in mind.  But either way, I take your point
that I have misremembered how it works.  I think I must have  formed
an incorrect mental model in my much earlier (but post-TCP!)
encounters with sockets.  And, at least right now, I wasn't clear on
the distinction between sockets and ports until you clarified. (This
is within port-based networking; I realize that systemd sockets also
include other connection methods than TCP ports).  So thank you.

Ross