Asyncore module provides the basic infrastructure for writing asynchronous socket service clients and servers.
There are only two ways to have a program on a single processor do more than one thing at a time. Multi-threaded programming is the simplest and most popular way to do it, but there is another very different technique, that lets you have nearly all the advantages of multi-threading, without actually using multiple threads. It's really only practical if your program is largely I/O bound. If your program is processor bound, then pre-emptive scheduled threads are probably what you really need. Network servers are rarely processor bound, however.
If your operating system supports the select() system call in its I/O library (and nearly all do), then you can use it to juggle multiple communication channels at once; doing other work while your I/O is taking place in the background. Although this strategy can seem strange and complex, especially at first, it is in many ways easier to understand and control than multi-threaded programming. The asyncore module solves many of the difficult problems for you, making the task of building sophisticated high-performance network servers and clients a snap.
Once the initial channel is created, calling the loop() function starts channel service, which continues until the last channel (including any that have been added to the map during asynchronous service) is closed.
asyncore.loop([timeout[, use_poll[, map[, count]]]]):
It enter a polling loop that terminates after count passes or all open channels have been closed. All arguments are optional. The count parameter defaults to None, resulting in the loop terminating only when all channels have been closed. The timeout argument sets the timeout parameter for the appropriate select() or poll() call, measured in seconds; the default is 30 seconds. The use_poll parameter, if true, indicates that poll() should be used in preference to select() (the default is False).