Twisted supports an abstraction over raw threads — using a thread as a deferred source. Thus, a deferred is returned immediately, which will receive a value when the thread finishes. Callbacks can be attached which will run in the main thread, thus alleviating the need for complex locking solutions.

Twisted is an event-driven networking engine written in the Python language. It is used to create servers for protocols such as SSH, proxy, SMTP, and HTTP. This tool addresses several weaknesses of existing Python networking platforms. It utilizes event-driven programming rather than multi-threaded programming.