Twisted is a networking engine written in Python, supporting numerous protocols. It contains a web server, numerous chat clients, chat servers, mail servers, and more.
Twisted is a platform for developing internet applications. While python, by itself, is a very powerful language, there are many facilities it lacks which other languages have spent great attention to adding. It can do this now; Twisted is a good (if somewhat idiosyncratic) pure-python framework or library, depending on how you treat it, and it continues to improve.
As a platform, Twisted should be focused on integration. Ideally, all functionality will be accessible through all protocols. Failing that, all functionality should be configurable through at least one protocol, with a seamless and consistent user-interface. The next phase of development will be focusing strongly on a configuration system which will unify many disparate pieces of the current infrastructure, and allow them to be tacked together by a non-programmer.
A fundamental feature of network programming is that of waiting for data. Imagine you have a function which sends an email summarising some information. This function needs to connect to a remote server, wait for the remote server to reply, check that the remote server can process the email, wait for the reply, send the email, wait for the confirmation, and then disconnect.
Any one of these steps may take a long period of time. Your program might use the simplest of all possible models, in which it actually sits and waits for data to be sent and received, but in this case it has some very obvious and basic limitations: it can't send many emails at once; and in fact it can't do anything else while it is sending an email.
Hence, all but the simplest network programs avoid this model. You can use one of several different models to allow your program to keep doing whatever tasks it has on hand while it is waiting for something to happen before a particular task can continue.
Twisted has a knowledgeable, energetic, and growing developer community. Members of this community have concern over issues like those you will be facing in your custom server development and have solved those issues for themselves already within the Twisted framework.