Подсказки для разработки веб-сервера
Я нашел решение: чтобы анимация не перекрывала текущее значение свойства, удалите его или присвойте ему FillBehavior из Stop .
6 ответов
A web server starts out as being an extremely simple piece of code:
- open a TCP/IP socket on port 80
- while not terminated
- wait for connections on that socket
- when someone sends you HTTP headers
- find the path to the file
- copy the file to the socket
So the outline of the code is easy.
Now, you have some complexities to handle:
- in the simplest version of the code, while you're talking to one browser, all the others can't connect. You need to come up with some way of handling multiple connections.
- it's often convenient to be able to send out something more than just a static file (although the first HTTP servers did exactly that) so you need to be able to run other programs.
Handling the possibility of multiple connections is also relatively easy, with a number of possible choices.
- the simplest version (again, this is the way it was done originally) is to have the code that listens to port 80 set up a specific socket for that connection, then fork a copy of itself to handle that one connection. That process runs until the socket is closed, and then terminates. However, that's relatively expensive: a fork takes tens of milliseconds in general, so that limits how fast you can run.
- The second choice is to create a lightweight process — a/k/a a thread — to process the request.
Running a program is actually fairly easy too. In general, you define a special path to a CGI directory; a URL that has a path through that directory then interprets the path name as the path to a program. The server would then create a subprocess using fork/exec, with STDOUT connected to the socket. The program then runs, sending output to STDOUT, and it is sent on to the client browser.
This is the basic pattern; everything else a web server does is just adding frills and additional functionality to this basic pattern.
Here are some other sources for example code:
- http://www.codeproject.com/KB/IP/Generic_TCP_IP_server.aspx
- http://cs.baylor.edu/~donahoo/practical/CSockets/textcode.html
- http://www.paulgriffiths.net/program/c/echoserv.php
- http://www.linuxhowtos.org/C_C++/socket.htm
It pretty much does nothing of what you really wanted, but for simple it's hard to beat this one from http://www.commandlinefu.com:
$ python -m SimpleHTTPServer
Firstly, please don't let this become a usable project - getting security right for web servers is really hard.
Ok, here are things to keep in mind:
- The thread that accepts connections needs to hand off to background threads as soon as possible.
- You can't have a thread for every single connection - with large volumes you'll run out of your thread limit.
- Use some kind of a worker thread pool to handle your requests.
- Ensure that you scrub the URL when you get an HTTP GET request. So I couldn't do something like http://localhost/../../Users/blah/ to get higher level access.
- Ensure you always set the relevant content and mime types.
Good luck - this is a hell of a job.
The networking et al are pretty standard fair, so don't worry so much about that. (there are several "instant", sample network servers in most any language.)
Instead, focus on actually implementing the HTTP specification. You'll be amazed at a) what you don't know and b) how much things that are supposed to be HTTP compliant, really aren't, but fake it well.
Then you'll marvel that the web works at all.
When you're done with HTTP, enjoy trying to implement IMAP.
I wrote a light webserver in Python a few years back, also as a learning project.
The simplest piece of advice I can give, especially as a learning project, is build a core that works, then iterative design on top of that. Don't aim for the moon right off the hop, start very small, then add featuers, refine and continue. I would recommend using a tool that encourages expermentation, like Python, where you can literally type and test code at the same time.
Я подумывал начать тот же проект, чтобы лучше изучить Python. Класс BaseHTTPServer - неплохая отправная точка.
В курсе, который я проводил, было задание по доверенности, так что я могу пролить свет здесь, я думаю.
Итак, вы собираетесь в конечном итоге делать много изменений заголовков, просто чтобы облегчить тебе жизнь. А именно, с HTTP / 1.0 гораздо проще работать, чем с HTTP / 1.1. Вы не хотите иметь дело с управлением тайм-аутами, сообщениями поддержки активности и тому подобным. Проще всего одно соединение на транзакцию.
Вы будете выполнять много-много синтаксического анализа. Анализировать сложно в C. Я бы посоветовал вам написать функцию, похожую на
int readline(char *buff, int maxLen) {
while((c = readNextCharFromSocket(&s)) && c != '\n' && i < maxLen)
buff[i++] = c;
return i;
}
, и обрабатывать ее по одной строке за раз, исключительно потому, что проще всего использовать существующие строковые функции C по одной строке за раз. Также помните, что строки разделены \ r \ n, а заголовки заканчиваются \ r \ n \ r \ n.
Самым сложным будет синтаксический анализ,