简易Web服务器-蒲公英云

基础知识点

首先简单认识TCP/IP协议
请访问http://www.cnblogs.com/roverliang/p/5176456.html

TCP/IP协议族中有一个重要的概念是分层，TCP/IP协议按照层次分为以下四层
这里写图片描述

TCP/IP通信数据流
这里写图片描述

使用HTTP协议进行数据传输的过程

这里写图片描述

HTTP请求报文
这里写图片描述

HTTP响应报文
这里写图片描述

TCP协议三次握手过程分析
请访问 http://blog.csdn.net/wwwdc1012/article/details/77857265

Python CGI编程 : http://www.runoob.com/python/python-cgi.html
CGI(Common Gateway Interface),通用网关接口,它是一段程序,运行在服务器上如：HTTP服务器，提供同客户端HTML页面的接口。

Python BaseHTTPServer 模块解析
http://blog.csdn.net/xhw88398569/article/details/49179967

下面为一个简单的Web服务器

该服务器工作流程：
(1) 定义多个可能遇到的多种情况及对应的处理方法：
是否是 cgi 请求 -> 文件是否存在 -> 目录下是否存在index.html -> 目录下是否不存在index.html -> 其他情况

Cases = [case_no_file(),
             case_cgi_file(),
             case_existing_file(),
             case_directory_index_file(),
             case_directory_no_index_file(),
             case_always_fail()]

(2) 逐个检查匹配到哪种情况，并处理

for case in self.Cases:
                if case.test(self):
                    case.act(self)
                    break
import sys, os, BaseHTTPServer
#-----------------------------------------------------------
# 服务器异常类
class ServerException(Exception):
    '''For internal error reporting.'''
    pass
#-----------------------------------------------------------
class base_case(object):
    '''Parent for case handlers.'''
    def handle_file(self, handler, full_path):
        """处理文件，例如读取 index.html 文件，然后输出到响应报文中 """
        try:
            with open(full_path, 'rb') as reader:
                content = reader.read()
            handler.send_content(content)
        except IOError as msg:
            msg = "'{0}' cannot be read: {1}".format(full_path, msg)
            handler.handle_error(msg) # 异常信息
    def index_path(self, handler):
        """合成index.html的全路径 """
        return os.path.join(handler.full_path, 'index.html')
    def test(self, handler):
        assert False, 'Not implemented.'
    def act(self, handler):
        assert False, 'Not implemented.'
#-----------------------------------------------------------
class case_no_file(base_case):
    '''File or directory does not exist. 给一个路径名称，文件或目录都不存在的情况 '''
    def test(self, handler):
        # 测试路径是否存在
        return not os.path.exists(handler.full_path)
    def act(self, handler):
        # 不存在时执行的动作，返回服务器异常
        raise ServerException("'{0}' not found".format(handler.path))
#-----------------------------------------------------------
class case_cgi_file(base_case):
    '''Something runnable. cgi，当服务器上的脚本存在时则执行脚本，返回执行结果 '''
    def run_cgi(self, handler):  # 执行脚本
        cmd = "python " + handler.full_path
        child_stdin, child_stdout = os.popen2(cmd)
        child_stdin.close()
        data = child_stdout.read()
        child_stdout.close()
        handler.send_content(data)
    def test(self, handler):  # 测试脚本是否存在
        return os.path.isfile(handler.full_path) and \
               handler.full_path.endswith('.py')
    def act(self, handler):
        self.run_cgi(handler)
#-----------------------------------------------------------
class case_existing_file(base_case):
    '''File exists. 给一个文件名，当文件存在时，处理 '''
    def test(self, handler):
        return os.path.isfile(handler.full_path)
    def act(self, handler):
        self.handle_file(handler, handler.full_path)
#-----------------------------------------------------------
class case_directory_index_file(base_case):
    '''Serve index.html page for a directory. 给一个目录名，当该目录下存在index.html时，处理并返回该index.html '''
    def test(self, handler):
        return os.path.isdir(handler.full_path) and \
               os.path.isfile(self.index_path(handler))
    def act(self, handler):
        self.handle_file(handler, self.index_path(handler))
#-----------------------------------------------------------
class case_directory_no_index_file(base_case):
    '''Serve listing for a directory without an index.html page. 目录下不存在index.html时，列出该目录下的所有文件，并渲染到简单的模板中 '''
    # How to display a directory listing.
    Listing_Page = '''\ <html> <body> <ul> {0} </ul> </body> </html> '''
    def list_dir(self, handler, full_path):
        try:
            entries = os.listdir(full_path)
            bullets = ['<li>{0}</li>'.format(e) for e in entries if not e.startswith('.')]
            page = self.Listing_Page.format('\n'.join(bullets))
            handler.send_content(page)
        except OSError as msg:
            msg = "'{0}' cannot be listed: {1}".format(self.path, msg)
            handler.handle_error(msg)
    def test(self, handler):
        return os.path.isdir(handler.full_path) and \
               not os.path.isfile(self.index_path(handler))
    def act(self, handler):
        self.list_dir(handler, handler.full_path)
#------------------------------------------------------
class case_always_fail(base_case):
    '''Base case if nothing else worked. 当之前所有的情况都失败时，执行这个 '''
    def test(self, handler):
        return True
    def act(self, handler):
        raise ServerException("Unknown object '{0}'".format(handler.path))
#------------------------------------------------------
class RequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
    ''' If the requested path maps to a file, that file is served. If anything goes wrong, an error page is constructed. '''
    Cases = [case_no_file(),
             case_cgi_file(),
             case_existing_file(),
             case_directory_index_file(),
             case_directory_no_index_file(),
             case_always_fail()]
    # How to display an error. 显示错误信息的模板
    Error_Page = """\ <html> <body> <h1>Error accessing {path}</h1> <p>{msg}</p> </body> </html> """
    # Classify and handle request. 处理GET请求
    def do_GET(self):
        try:
            # Figure out what exactly is being requested.
            self.full_path = os.getcwd() + self.path
            # Figure out how to handle it.
            for case in self.Cases:
                if case.test(self):
                    case.act(self)
                    break
        # Handle errors.
        except Exception as msg:
            self.handle_error(msg)
    # Handle unknown objects.
    def handle_error(self, msg):
        content = self.Error_Page.format(path=self.path, msg=msg)
        self.send_content(content, 404)
    # Send actual content. 设置响应报文
    def send_content(self, content, status=200):
        self.send_response(status)
        self.send_header("Content-type", "text/html")
        self.send_header("Content-Length", str(len(content)))
        self.end_headers()
        self.wfile.write(content)
#-------------------------------------------------------------------------------
if __name__ == '__main__':
    serverAddress = ('', 8080)
    server = BaseHTTPServer.HTTPServer(serverAddress, RequestHandler)
    server.serve_forever()

参考：500 lines or less 中文翻译计划《简易Web服务器》
https://github.com/HT524/500LineorLess_CN/blob/master/%E7%AE%80%E6%98%93web%E6%9C%8D%E5%8A%A1%E5%99%A8%20A%20simple%20web%20server/%E7%AE%80%E6%98%93web%E6%9C%8D%E5%8A%A1%E5%99%A8.md