Tom Anderson wrote: > On Sun, 21 Aug 2005, John Walton wrote: > > >>Hello, everyone. I just began school, and they already assigned us >>science fair. Since I'm in 8th grade, I get to do demonstrations for >>our projects. I'm probably going to demonstrate Python's networking >>capabilities by writing a simple instant messenger program. I only have >>a few problems: >> >>1. I know squat about Python network Programming >> >>2. I know nothing about networks >> >>So if any of you know of a good Python Networking Tutorial or a website >>with lots of information on networks and networking, please reply. >>Thanks! > > > There are two sides to this problem. The first is understanding networks > in general, and the specific application protocols you're interested in. > When i say 'understanding networks in general', don't panic - i don't mean > you need to understand everything about how the internet works. In fact, > you don't really need to understand *anything* about how the internet > works, you just need to understand the interfaces it exposes to you. And, > helpfully, that interface is pretty simple: a program can get a connection > to another program, running on a different machine, which amounts ot a > pipe for bytes - both ends can write bytes to the pipe when they feel like > it, and those bytes become available for the other end to read. To open > one of these connections, you need to know the hostname or IP address of > the computer at the far end, and something called a 'port number', which > is basically a way of identifying which program on that machine you want > to talk to; if you want other programs to be able to open connections to > your program, you have to pick a port number and ask the system to give > you any connections that are made to it. > > That's pretty much it for the network fundamentals. There is more - > datagram sockets, looking up IP addresses, doing funky things with sockets > - but you can forget about that until you've mastered the basics. > I tried to cover those basics as briefly as possible in the tutorial I mentioned earlier. I'd appreciate your comments on how well I succeeded.
> What you do need to understand beyond this, though, is about the > application protocol you're using. The network just gives you a way to > move streams of bytes; in order to actually do anything useful, you need > an agreement between the programs at either end of the connection about > what those bytes mean - that's an application protocol. It's basically a > file format as applied to a network connection instead of a file. Each > application protocol is completely different to every other one (well, > there are a lot of similarities, but they're mostly different), so you'll > need to read up on the one you want to use (or invent your own!) - the > documentation is (almost always) in the form of a document unhelpfully > called a Request For Comments, or RFC; the internet RFCs are published > here: > > http://www.rfc-editor.org/ > > For example, here's the RFC for HTTP version 1.0: > > http://www.rfc-editor.org/rfc/rfc1945.txt > > RFCs can be pretty heavy going, but they are *the* definitive > specifications, so they're worth reading. Once you're used to them, > they're often easier to read than tutorials, i find. > Not for newbies, though very useful for ensuring high levels of interoperability (and fascinating when you start to realize that real products bend the RFCs in various ways). > The second thing is understanding how to do network programming in python. > There's a well-established API in C for network programming - the socket > API - which comes from UNIX; python uses a fairly simple translation of > this as its network API (look in the 'socket' package). The good thing > about this is that this API is well-understood and well-documented. The > bad thing is that it's a bit of a mess (compare and contrast to the API in > Java if you don't believe me). There's detailed documentation for the > socket module here: > > http://docs.python.org/lib/module-socket.html > [...] But then Java's a bit of a mess as a language when compared with Python, I should say. While I know the language has many adherents, it also seems to have many programmers who only know enough to follow recipes. This latter feature is a symptom of the language's popularity, so I suppose we should expect the same problems in about twenty years when Python becomes more popular than Java. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
