I’ve been dealing with this same exception in my application, and I finally found a helpful suggestion from this post – http://httpcomponents.10934.n7.nabble.com/I-O-reactor-status-STOPPED-td29059.html
You can use #getAuditLog() method of the I/O reactor to find out exactly
what exception caused it to terminate.
If you keep a reference to your ConnectionManager’s IOReactor, you can call this method to get insight into the actual problem:
http://hc.apache.org/httpcomponents-core-4.4.x/httpcore-nio/apidocs/org/apache/http/impl/nio/reactor/AbstractMultiworkerIOReactor.html#getAuditLog()
Turns out I was doing something incredibly stupid in my own code. But I couldn’t figure it out until I read the audit log.