http.server —- HTTP 服务器

源代码：Lib/http/server.py

这个模块定义了实现 HTTP 服务器（ Web 服务器）的类。

警告

不推荐在生产环境中使用 http.server 。它只实现了基本的安全检查功能。

HTTPServer 是 socketserver.TCPServer 的一个子类。它会创建和侦听 HTTP 套接字，并将请求调度给处理程序。用于创建和运行服务器的代码看起来像这样：

  1. def run(server_class=HTTPServer, handler_class=BaseHTTPRequestHandler):
  2.     server_address = ('', 8000)
  3.     httpd = server_class(server_address, handler_class)
  4.     httpd.serve_forever()
  • class http.server.HTTPServer(server_address, RequestHandlerClass)
  • 该类基于 TCPServer 类，并会将服务器地址存入名为 server_name 和 server_port 的实例变量中。服务器可被处理程序通过 server 实例变量访问。
  • class http.server.ThreadingHTTPServer(server_address, RequestHandlerClass)
  • This class is identical to HTTPServer but uses threads to handlerequests by using the ThreadingMixIn. Thisis useful to handle web browsers pre-opening sockets, on whichHTTPServer would wait indefinitely.

3.7 新版功能.

The HTTPServer and ThreadingHTTPServer must be givena RequestHandlerClass on instantiation, of which this moduleprovides three different variants:

  • class http.server.BaseHTTPRequestHandler(request, client_address, server)
  • This class is used to handle the HTTP requests that arrive at the server. Byitself, it cannot respond to any actual HTTP requests; it must be subclassedto handle each request method (e.g. GET or POST).BaseHTTPRequestHandler provides a number of class and instancevariables, and methods for use by subclasses.

The handler will parse the request and the headers, then call a methodspecific to the request type. The method name is constructed from therequest. For example, for the request method SPAM, the doSPAM()method will be called with no arguments. All of the relevant information isstored in instance variables of the handler. Subclasses should not need tooverride or extend the [init()](https://docs.python.org/zh-cn/3.7/reference/datamodel.html#object.__init_) method.

BaseHTTPRequestHandler has the following instance variables:

  • client_address

  • Contains a tuple of the form (host, port) referring to the client'saddress.

  • server

  • Contains the server instance.

  • close_connection

  • Boolean that should be set before handle_one_request() returns,indicating if another request may be expected, or if the connection shouldbe shut down.

  • requestline

  • Contains the string representation of the HTTP request line. Theterminating CRLF is stripped. This attribute should be set byhandle_one_request(). If no valid request line was processed, itshould be set to the empty string.

  • command

  • Contains the command (request type). For example, 'GET'.

  • path

  • Contains the request path.

  • request_version

  • Contains the version string from the request. For example, 'HTTP/1.0'.

  • headers

  • Holds an instance of the class specified by the MessageClass classvariable. This instance parses and manages the headers in the HTTPrequest. The parse_headers() function fromhttp.client is used to parse the headers and it requires that theHTTP request provide a valid RFC 2822 style header.

  • rfile

  • An io.BufferedIOBase input stream, ready to read fromthe start of the optional input data.

  • wfile

  • Contains the output stream for writing a response back to theclient. Proper adherence to the HTTP protocol must be used when writing tothis stream in order to achieve successful interoperation with HTTPclients.

在 3.6 版更改: This is an io.BufferedIOBase stream.

BaseHTTPRequestHandler has the following attributes:

  • server_version

  • Specifies the server software version. You may want to override this. Theformat is multiple whitespace-separated strings, where each string is ofthe form name[/version]. For example, 'BaseHTTP/0.2'.

  • sys_version

  • Contains the Python system version, in a form usable by theversion_string method and the server_version classvariable. For example, 'Python/1.4'.

  • error_message_format

  • Specifies a format string that should be used by send_error() methodfor building an error response to the client. The string is filled bydefault with variables from responses based on the status codethat passed to send_error().

  • error_content_type

  • Specifies the Content-Type HTTP header of error responses sent to theclient. The default value is 'text/html'.

  • protocol_version

  • This specifies the HTTP protocol version used in responses. If set to'HTTP/1.1', the server will permit HTTP persistent connections;however, your server must then include an accurate Content-Lengthheader (using send_header()) in all of its responses to clients.For backwards compatibility, the setting defaults to 'HTTP/1.0'.

  • MessageClass

  • Specifies an email.message.Message-like class to parse HTTPheaders. Typically, this is not overridden, and it defaults tohttp.client.HTTPMessage.

  • responses

  • This attribute contains a mapping of error code integers to two-element tuplescontaining a short and long message. For example, {code: (shortmessage,longmessage)}. The shortmessage is usually used as the message key in anerror response, and longmessage as the explain key. It is used bysend_response_only() and send_error() methods.

A BaseHTTPRequestHandler instance has the following methods:

  • handle()

  • Calls handle_one_request() once (or, if persistent connections areenabled, multiple times) to handle incoming HTTP requests. You shouldnever need to override it; instead, implement appropriate do_*()methods.

  • handle_one_request()

  • This method will parse and dispatch the request to the appropriatedo_*() method. You should never need to override it.

  • handle_expect_100()

  • When a HTTP/1.1 compliant server receives an Expect: 100-continuerequest header it responds back with a 100 Continue followed by 200OK headers.This method can be overridden to raise an error if the server does notwant the client to continue. For e.g. server can chose to send 417Expectation Failed as a response header and return False.

3.2 新版功能.

  • senderror(_code, message=None, explain=None)
  • Sends and logs a complete error reply to the client. The numeric code_specifies the HTTP error code, with _message as an optional, short, humanreadable description of the error. The explain argument can be used toprovide more detailed information about the error; it will be formattedusing the error_message_format attribute and emitted, aftera complete set of headers, as the response body. The responsesattribute holds the default values for message and explain thatwill be used if no value is provided; for unknown codes the default valuefor both is the string ???. The body will be empty if the method isHEAD or the response code is one of the following: 1xx,204 No Content, 205 Reset Content, 304 Not Modified.

在 3.4 版更改: The error response includes a Content-Length header.Added the explain argument.

  • sendresponse(_code, message=None)
  • Adds a response header to the headers buffer and logs the acceptedrequest. The HTTP response line is written to the internal buffer,followed by Server and Date headers. The values for these two headersare picked up from the version_string() anddate_time_string() methods, respectively. If the server does notintend to send any other headers using the send_header() method,then send_response() should be followed by an end_headers()call.

在 3.3 版更改: Headers are stored to an internal buffer and end_headers()needs to be called explicitly.

  • sendheader(_keyword, value)
  • Adds the HTTP header to an internal buffer which will be written to theoutput stream when either end_headers() or flush_headers() isinvoked. keyword should specify the header keyword, with _value_specifying its value. Note that, after the send_header calls are done,end_headers() MUST BE called in order to complete the operation.

在 3.2 版更改: Headers are stored in an internal buffer.

  • sendresponse_only(_code, message=None)
  • Sends the response header only, used for the purposes when 100Continue response is sent by the server to the client. The headers notbuffered and sent directly the output stream.If the message is notspecified, the HTTP message corresponding the response code is sent.

3.2 新版功能.

  • end_headers()
  • Adds a blank line(indicating the end of the HTTP headers in the response)to the headers buffer and calls flush_headers().

在 3.2 版更改: The buffered headers are written to the output stream.

  • flush_headers()
  • Finally send the headers to the output stream and flush the internalheaders buffer.

3.3 新版功能.

  • logrequest(_code='-', size='-')

  • Logs an accepted (successful) request. code should specify the numericHTTP code associated with the response. If a size of the response isavailable, then it should be passed as the size parameter.

  • logerror(…_)

  • Logs an error when a request cannot be fulfilled. By default, it passesthe message to log_message(), so it takes the same arguments(format and additional values).

  • logmessage(_format, …)

  • Logs an arbitrary message to sys.stderr. This is typically overriddento create custom error logging mechanisms. The format argument is astandard printf-style format string, where the additional arguments tolog_message() are applied as inputs to the formatting. The clientip address and current date and time are prefixed to every message logged.

  • version_string()

  • Returns the server software's version string. This is a combination of theserver_version and sys_version attributes.

  • datetime_string(_timestamp=None)

  • Returns the date and time given by timestamp (which must be None or inthe format returned by time.time()), formatted for a messageheader. If timestamp is omitted, it uses the current date and time.

The result looks like 'Sun, 06 Nov 1994 08:49:37 GMT'.

  • log_date_time_string()

  • Returns the current date and time, formatted for logging.

  • address_string()

  • Returns the client address.

在 3.3 版更改: Previously, a name lookup was performed. To avoid name resolutiondelays, it now always returns the IP address.

  • class http.server.SimpleHTTPRequestHandler(request, client_address, server, directory=None)
  • This class serves files from the current directory and below, directlymapping the directory structure to HTTP requests.

A lot of the work, such as parsing the request, is done by the base classBaseHTTPRequestHandler. This class implements the do_GET()and do_HEAD() functions.

The following are defined as class-level attributes ofSimpleHTTPRequestHandler:

  • server_version

  • This will be "SimpleHTTP/" + version, where version isdefined at the module level.

  • extensions_map

  • A dictionary mapping suffixes into MIME types. The default issignified by an empty string, and is considered to beapplication/octet-stream. The mapping is used case-insensitively,and so should contain only lower-cased keys.

  • directory

  • If not specified, the directory to serve is the current working directory.

The SimpleHTTPRequestHandler class defines the following methods:

  • do_HEAD()

  • This method serves the 'HEAD' request type: it sends the headers itwould send for the equivalent GET request. See the do_GET()method for a more complete explanation of the possible headers.

  • do_GET()

  • The request is mapped to a local file by interpreting the request as apath relative to the current working directory.

If the request was mapped to a directory, the directory is checked for afile named index.html or index.htm (in that order). If found, thefile's contents are returned; otherwise a directory listing is generatedby calling the list_directory() method. This method usesos.listdir() to scan the directory, and returns a 404 errorresponse if the listdir() fails.

If the request was mapped to a file, it is opened. Any OSErrorexception in opening the requested file is mapped to a 404,'File not found' error. If there was a 'If-Modified-Since'header in the request, and the file was not modified after this time,a 304, 'Not Modified' response is sent. Otherwise, the contenttype is guessed by calling the guesstype() method, which in turnuses the _extensions_map variable, and the file contents are returned.

A 'Content-type:' header with the guessed content type is output,followed by a 'Content-Length:' header with the file's size and a'Last-Modified:' header with the file's modification time.

Then follows a blank line signifying the end of the headers, and then thecontents of the file are output. If the file's MIME type starts withtext/ the file is opened in text mode; otherwise binary mode is used.

For example usage, see the implementation of the test() functioninvocation in the http.server module.

在 3.7 版更改: Support of the 'If-Modified-Since' header.

The SimpleHTTPRequestHandler class can be used in the followingmanner in order to create a very basic webserver serving files relative tothe current directory:

  1. import http.server
  2. import socketserver
  3.  
  4. PORT = 8000
  5.  
  6. Handler = http.server.SimpleHTTPRequestHandler
  7.  
  8. with socketserver.TCPServer(("", PORT), Handler) as httpd:
  9.     print("serving at port", PORT)
  10.     httpd.serve_forever()

http.server can also be invoked directly using the -mswitch of the interpreter with a port number argument. Similar tothe previous example, this serves files relative to the current directory:

  1. python -m http.server 8000

By default, server binds itself to all interfaces. The option -b/—bindspecifies a specific address to which it should bind. For example, thefollowing command causes the server to bind to localhost only:

  1. python -m http.server 8000 --bind 127.0.0.1

3.4 新版功能: —bind argument was introduced.

By default, server uses the current directory. The option -d/—directoryspecifies a directory to which it should serve the files. For example,the following command uses a specific directory:

  1. python -m http.server --directory /tmp/

3.7 新版功能: —directory specify alternate directory

  • class http.server.CGIHTTPRequestHandler(request, client_address, server)
  • This class is used to serve either files or output of CGI scripts from thecurrent directory and below. Note that mapping HTTP hierarchic structure tolocal directory structure is exactly as in SimpleHTTPRequestHandler.

注解

CGI scripts run by the CGIHTTPRequestHandler class cannot executeredirects (HTTP code 302), because code 200 (script output follows) issent prior to execution of the CGI script. This pre-empts the statuscode.

The class will however, run the CGI script, instead of serving it as a file,if it guesses it to be a CGI script. Only directory-based CGI are used —-the other common server configuration is to treat special extensions asdenoting CGI scripts.

The do_GET() and do_HEAD() functions are modified to run CGI scriptsand serve the output, instead of serving files, if the request leads tosomewhere below the cgi_directories path.

The CGIHTTPRequestHandler defines the following data member:

  • cgi_directories
  • This defaults to ['/cgi-bin', '/htbin'] and describes directories totreat as containing CGI scripts.

The CGIHTTPRequestHandler defines the following method:

  • do_POST()
  • This method serves the 'POST' request type, only allowed for CGIscripts. Error 501, "Can only POST to CGI scripts", is output when tryingto POST to a non-CGI url.

Note that CGI scripts will be run with UID of user nobody, for securityreasons. Problems with the CGI script will be translated to error 403.

CGIHTTPRequestHandler can be enabled in the command line by passingthe —cgi option:

  1. python -m http.server --cgi 8000