iMac stopping connecting to other networked Macs

[Chupa Chupa]

I have 3 Macs, iMac, MBP, and Mini. All 3 are set up for network sharing in exactly the same way and functions. Recently the iMac connection fails -- both folder and "shared screen" even though MBP and Mini are listed as "shared" in the finder.

MBP and Mini still connect with each other no problem. It's only the iMac that won't connect or allow connections to it.

I've rechecked all the sharing settings and firewall, restarted the iMac. None of that works. Any other ideas?

 

[Lunder89]

Have you tried pinging the IP-adress of the iMac from one of the other Macs?

You can ping from the app Terminal with this command: ping -c 4 127.0.0.1
(replace 127.0.0.1 with the IP of the iMac)

If you do not get a response, they simply can't find each other. And there can be a number of reasons for that. A few to look into:
1. Is the clock in the Router correct
2. Does it help giving the Mac a fixed IP-adress from the router
3. If any port-forwarding is enabled, try to disable it
4. Maybe the firewall on the Mac is the problem, try to disable it, then re-run the ping

If you do get a response, then it is guaranteed that your setup, on the iMac is to blame, as something is blocking access to it. Returning all the settings to default and then trying to set it up again might help.
If you have any third-party firewalls, they might need a few extra settings or some tweaking.

If you by any chance is running OS X Yosemite, it might simply be a bug, since Yosemite has terrible networking (in my experience).

Network can a pain in the but to troubleshoot. Even in 2017 :-(