简易Web服务器

迈不过友情╰ 2022-06-08 10:00 161阅读 0赞

## 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][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][SouthEast]

TCP/IP通信数据流  
![这里写图片描述][SouthEast 1]

使用HTTP协议进行数据传输的过程

![这里写图片描述][SouthEast 2]

HTTP请求报文  
![这里写图片描述][SouthEast 3]

HTTP响应报文  
![这里写图片描述][SouthEast 4]

TCP协议三次握手过程分析  
请访问 [http://blog.csdn.net/wwwdc1012/article/details/77857265][http_blog.csdn.net_wwwdc1012_article_details_77857265]

Python CGI编程 : [http://www.runoob.com/python/python-cgi.html][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][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][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]

[http_www.cnblogs.com_roverliang_p_5176456.html]: http://www.cnblogs.com/roverliang/p/5176456.html
[SouthEast]: /images/20220608/0aae51884eca41adacb789578880254f.png
[SouthEast 1]: /images/20220608/b54ef492a1404f88be2dec402ca0786e.png
[SouthEast 2]: /images/20220608/e9eaf13c17ee41208905a2e7de255ef9.png
[SouthEast 3]: /images/20220608/75629a7f7a0a43078c82375d64866c74.png
[SouthEast 4]: /images/20220608/d7d5528be1a843559c18278bed1d4548.png
[http_blog.csdn.net_wwwdc1012_article_details_77857265]: http://blog.csdn.net/wwwdc1012/article/details/77857265
[http_www.runoob.com_python_python-cgi.html]: http://www.runoob.com/python/python-cgi.html
[http_blog.csdn.net_xhw88398569_article_details_49179967]: http://blog.csdn.net/xhw88398569/article/details/49179967
[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]: 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