Fix Messages Stuck Offline on OSX

Update: Nino (see comments) has written a blog post on how to automate this a little, read it at http://rubyengineer.com/posts/2

If you have an issue with Messages on OSX being stuck in ‘Offline’ mode that won’t connect, open up Terminal and type the following:

ps auxwww | grep imagent

This will give you output similar to:

scott             341   0.0  0.3  2502924  12828   ??  S     1:41pm   0:04.75 /System/Library/PrivateFrameworks/IMCore.framework/imagent.app/Contents/MacOS/imagent
scott           23666   0.0  0.0  2432772    460 s003  R+    9:25am   0:00.00 grep imagent

The number you’re looking for is 341, which is the process ID of imagent.

Now, type:

kill -9 341

and the process will be restarted, allowing you to change status to online.