Q I have three Macs running OS X 10.11.2 here, all networked together, and all with file sharing enabled in their Sharing pane. My old Mac mini and iMac 27″ can see one another fine and connect, and my iMac 21.5″ can connect to them. But for some strange reason when I try to do the same from either the mini or the iMac 27″ to the 21.5″, after a few seconds I am told that the connection has failed. What is wrong?
A Before going any further, make a note of the IP address of each, and using Network Utility, ping each from the other two. This should verify that their network connections are sound, and they are able to share files.
Next, open the Sharing pane on each, ensure that File Sharing is enabled, and click on its Options… button. Check that files and folders are being shared using AFP. If they already are, try turning off sharing using SMB. Then on each, try connecting using the Finder’s Go/Connect to Server… menu command, pointing it at the afp:// addresses which you have recorded.
If that still does not work, try connecting using the short usernames in each case. Any further errors should take you straight to Console’s logs to see what is being recorded there.
(In fact, it turned out that only SMB was enabled on the iMac 21.5″. Unfortunately SMB is notorious for such strange quirks, and should be avoided if AFP is available, such as between Macs.)