http.server — HTTP 服务器

源代码： Lib/http/server.py

This module defines classes for implementing HTTP servers.

警告

http.server is not recommended for production. It only implements basic security checks.

Availability: not Emscripten, not WASI.

This module does not work or is not available on WebAssembly platforms wasm32-emscripten and wasm32-wasi. See WebAssembly platforms for more information.

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：

def run(server_class=HTTPServer, handler_class=BaseHTTPRequestHandler):
    server_address = ('', 8000)
    httpd = server_class(server_address, handler_class)
    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)

这个类与 HTTPServer 相似，但会通过使用 ThreadingMixIn 来以线程处理请求。 这适用于处理 Web 浏览器预开启套接字，以便 HTTPServer 无限期地执行等待。

3.7 新版功能.

HTTPServer 和 ThreadingHTTPServer 必须在实例化时给定一个 RequestHandlerClass，此模块提供了该对象的三种不同形式:

class http.server.BaseHTTPRequestHandler(request, client_address, server)

这个类用于处理到达服务器的 HTTP 请求。 它本身无法响应任何实际的 HTTP 请求；它必须被子类化以处理每个请求方法（例如 GET 或 POST）。 BaseHTTPRequestHandler 提供了许多供子类使用的类和实例变量以及方法。

这个处理程序将解析请求和标头，然后调用特定请求类型对应的方法。 方法名称将根据请求来构造。 例如，对于请求方法 SPAM，将不带参数地调用 do_SPAM() 方法。 所有相关信息会被保存在该处理程序的实际变量中。 子类不需要重载或扩展 __init__() 方法。

BaseHTTPRequestHandler 具有下列实例变量:

client_address

包含 (host, port) 形式的指向客户端地址的元组。

server

包含服务器实例。

close_connection

应当在 handle_one_request() 返回之前设定的布尔值，指明是否要期待另一个请求，还是应当关闭连接。

requestline

包含 HTTP 请求行的字符串表示。 末尾的 CRLF 会被去除。 该属性应当由 handle_one_request() 来设定。 如果无有效请求行被处理，则它应当被设为空字符串。

command

包含具体的命令（请求类型）。 例如 'GET'。

path

包含请求路径。如果URL的查询部分存在， path 会包含这个查询部分。使用 RFC 3986 的术语来说，在这里， path 包含 hier-part 和 query 。

request_version

包含请求的版本字符串。 例如 'HTTP/1.0'。

headers

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

rfile

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

wfile

Contains the output stream for writing a response back to the client. Proper adherence to the HTTP protocol must be used when writing to this stream in order to achieve successful interoperation with HTTP clients.

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

BaseHTTPRequestHandler 具有下列属性：

server_version

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

sys_version

Contains the Python system version, in a form usable by the version_string method and the server_version class variable. For example, 'Python/1.4'.

error_message_format

Specifies a format string that should be used by send_error() method for building an error response to the client. The string is filled by default with variables from responses based on the status code that passed to send_error().

error_content_type

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

protocol_version

Specifies the HTTP version to which the server is conformant. It is sent in responses to let the client know the server’s communication capabilities for future requests. If set to 'HTTP/1.1', the server will permit HTTP persistent connections; however, your server must then include an accurate Content-Length header (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 HTTP headers. Typically, this is not overridden, and it defaults to http.client.HTTPMessage.

responses

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

A BaseHTTPRequestHandler instance has the following methods:

handle()

Calls handle_one_request() once (or, if persistent connections are enabled, multiple times) to handle incoming HTTP requests. You should never need to override it; instead, implement appropriate do_*() methods.

handle_one_request()

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

handle_expect_100()

When an HTTP/1.1 conformant server receives an Expect: 100-continue request header it responds back with a 100 Continue followed by 200 OK headers. This method can be overridden to raise an error if the server does not want the client to continue. For e.g. server can choose to send 417 Expectation Failed as a response header and return False.

3.2 新版功能.

send_error(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, human readable description of the error. The explain argument can be used to provide more detailed information about the error; it will be formatted using the error_message_format attribute and emitted, after a complete set of headers, as the response body. The responses attribute holds the default values for message and explain that will be used if no value is provided; for unknown codes the default value for both is the string ???. The body will be empty if the method is HEAD 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.

send_response(code, message=None)

Adds a response header to the headers buffer and logs the accepted request. The HTTP response line is written to the internal buffer, followed by Server and Date headers. The values for these two headers are picked up from the version_string() and date_time_string() methods, respectively. If the server does not intend 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.

send_header(keyword, value)

Adds the HTTP header to an internal buffer which will be written to the output stream when either end_headers() or flush_headers() is invoked. 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.

send_response_only(code, message=None)

Sends the response header only, used for the purposes when 100 Continue response is sent by the server to the client. The headers not buffered and sent directly the output stream.If the message is not specified, 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 internal headers buffer.

3.3 新版功能.

log_request(code='-', size='-')

Logs an accepted (successful) request. code should specify the numeric HTTP code associated with the response. If a size of the response is available, then it should be passed as the size parameter.

log_error(...)

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

log_message(format, ...)

Logs an arbitrary message to sys.stderr. This is typically overridden to create custom error logging mechanisms. The format argument is a standard printf-style format string, where the additional arguments to log_message() are applied as inputs to the formatting. The client ip 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 the server_version and sys_version attributes.

date_time_string(timestamp=None)

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

结果看起来像 'Sun, 06 Nov 1994 08:49:37 GMT'。

log_date_time_string()

返回当前的日期和时间，为日志格式化

address_string()

返回客户端的地址

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

class http.server.SimpleHTTPRequestHandler(request, client_address, server, directory=None)

This class serves files from the directory directory and below, or the current directory if directory is not provided, directly mapping the directory structure to HTTP requests.

3.7 新版功能: The directory parameter.

在 3.9 版更改: The directory parameter accepts a path-like object.

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

The following are defined as class-level attributes of SimpleHTTPRequestHandler:

server_version

This will be "SimpleHTTP/" + __version__, where __version__ is defined at the module level.

extensions_map

A dictionary mapping suffixes into MIME types, contains custom overrides for the default system mappings. The mapping is used case-insensitively, and so should contain only lower-cased keys.

在 3.9 版更改: This dictionary is no longer filled with the default system mappings, but only contains overrides.

The SimpleHTTPRequestHandler class defines the following methods:

do_HEAD()

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

do_GET()

这一请求通过把其解释为当前工作目录的相对路径来映射到本地文件

If the request was mapped to a directory, the directory is checked for a file named index.html or index.htm (in that order). If found, the file’s contents are returned; otherwise a directory listing is generated by calling the list_directory() method. This method uses os.listdir() to scan the directory, and returns a 404 error response if the listdir() fails.

If the request was mapped to a file, it is opened. Any OSError exception 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 content type is guessed by calling the guess_type() method, which in turn uses 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 the contents of the file are output. If the file’s MIME type starts with text/ the file is opened in text mode; otherwise binary mode is used.

For example usage, see the implementation of the test function in Lib/http/server.py.

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

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

import http.server
import socketserver

PORT = 8000

Handler = http.server.SimpleHTTPRequestHandler

with socketserver.TCPServer(("", PORT), Handler) as httpd:
    print("serving at port", PORT)
    httpd.serve_forever()

http.server can also be invoked directly using the -m switch of the interpreter. Similar to the previous example, this serves files relative to the current directory:

python -m http.server

The server listens to port 8000 by default. The default can be overridden by passing the desired port number as an argument:

python -m http.server 9000

By default, the server binds itself to all interfaces. The option -b/--bind specifies a specific address to which it should bind. Both IPv4 and IPv6 addresses are supported. For example, the following command causes the server to bind to localhost only:

python -m http.server --bind 127.0.0.1

3.4 新版功能: --bind argument was introduced.

3.8 新版功能: --bind argument enhanced to support IPv6

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

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

3.7 新版功能: --directory argument was introduced.

By default, the server is conformant to HTTP/1.0. The option -p/--protocol specifies the HTTP version to which the server is conformant. For example, the following command runs an HTTP/1.1 conformant server:

python -m http.server --protocol HTTP/1.1

3.11 新版功能: --protocol argument was introduced.

class http.server.CGIHTTPRequestHandler(request, client_address, server)

This class is used to serve either files or output of CGI scripts from the current directory and below. Note that mapping HTTP hierarchic structure to local directory structure is exactly as in SimpleHTTPRequestHandler.

备注

CGI scripts run by the CGIHTTPRequestHandler class cannot execute redirects (HTTP code 302), because code 200 (script output follows) is sent prior to execution of the CGI script. This pre-empts the status code.

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 as denoting CGI scripts.

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

The CGIHTTPRequestHandler defines the following data member:

cgi_directories

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

The CGIHTTPRequestHandler defines the following method:

do_POST()

This method serves the 'POST' request type, only allowed for CGI scripts. Error 501, “Can only POST to CGI scripts”, is output when trying to POST to a non-CGI url.

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

CGIHTTPRequestHandler can be enabled in the command line by passing the --cgi option:

python -m http.server --cgi

Security Considerations

SimpleHTTPRequestHandler will follow symbolic links when handling requests, this makes it possible for files outside of the specified directory to be served.