Chapter 3. Event-driven APIs
These APIs work by executing application event-handling functions in response to network activity. The library monitors network I/O and fires events. The event handlers run sequentially on the main library thread.
Because the event handlers run on the main library thread, the handler code must not contain any long-running blocking operations. Blocking in an event handler blocks all library execution. If you need to execute a long blocking operation, you must call it on a separate thread. The event-driven APIs include cross-thread communication facilities to support coordination between the library thread and application threads.
Long-running blocking calls in event handlers stop all library execution, preventing the library from handling other events and performing periodic tasks. Always start long-running blocking procedures in a separate application thread.