Check for POLLHUP when polling sockets

CollectAgent/simplemqttserverthread.cpp

@@ -291,6 +291,10 @@ void SimpleMQTTServerMessageThread::run()
                   cout << "fd(" << fds[connectionId].fd << ") revents: " << hex << fds[connectionId].revents << dec << "\n";
                   coutMtx.unlock();
 #endif
+                  /* Remote side hung up */
+                  if (fds[connectionId].revents & POLLHUP) {
+                      releaseConnection(connectionId);
+                  }
 
                   if (fds[connectionId].revents & POLLIN) {
                       char* readPtr;