"http.server" — HTTP servers
****************************

**Source code:** Lib/http/server.py

======================================================================

This module defines classes for implementing HTTP servers.

Warning:

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

Availability: not WASI.

This module does not work or is not available on WebAssembly. See
WebAssembly platforms for more information.

One class, "HTTPServer", is a "socketserver.TCPServer" subclass. It
creates and listens at the HTTP socket, dispatching the requests to a
handler.  Code to create and run the server looks like this:

   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)

   This class builds on the "TCPServer" class by storing the server
   address as instance variables named "server_name" and
   "server_port". The server is accessible by the handler, typically
   through the handler’s "server" instance variable.

   server_name

      The HTTP server’s fully qualified domain name.

   server_port

      The HTTP server’s port number obtained from *server_address*.

class http.server.ThreadingHTTPServer(server_address, RequestHandlerClass)

   This class is identical to HTTPServer but uses threads to handle
   requests by using the "ThreadingMixIn". This is useful to handle
   web browsers pre-opening sockets, on which "HTTPServer" would wait
   indefinitely.

   Added in version 3.7.

class http.server.HTTPSServer(server_address, RequestHandlerClass, bind_and_activate=True, *, certfile, keyfile=None, password=None, alpn_protocols=None)

   Subclass of "HTTPServer" with a wrapped socket using the "ssl"
   module. If the "ssl" module is not available, instantiating a
   "HTTPSServer" object fails with a "RuntimeError".

   The *certfile* argument is the path to the SSL certificate chain
   file, and the *keyfile* is the path to the file containing the
   private key.

   A *password* can be specified for files protected and wrapped with
   PKCS#8, but beware that this could possibly expose hardcoded
   passwords in clear.

   See also:

     See "ssl.SSLContext.load_cert_chain()" for additional information
     on the accepted values for *certfile*, *keyfile* and *password*.

   When specified, the *alpn_protocols* argument must be a sequence of
   strings specifying the “Application-Layer Protocol Negotiation”
   (ALPN) protocols supported by the server. ALPN allows the server
   and the client to negotiate the application protocol during the TLS
   handshake.

   By default, it is set to "["http/1.1"]", meaning the server
   supports HTTP/1.1.

   Added in version 3.14.

class http.server.ThreadingHTTPSServer(server_address, RequestHandlerClass, bind_and_activate=True, *, certfile, keyfile=None, password=None, alpn_protocols=None)

   This class is identical to "HTTPSServer" but uses threads to handle
   requests by inheriting from "ThreadingMixIn". This is analogous to
   "ThreadingHTTPServer" only using "HTTPSServer".

   Added in version 3.14.

The "HTTPServer", "ThreadingHTTPServer", "HTTPSServer" and
"ThreadingHTTPSServer" must be given a *RequestHandlerClass* on
instantiation, of which this module provides 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.  By itself, it cannot respond to any actual HTTP requests;
   it must be subclassed to handle each request method (for example,
   "'GET'" or "'POST'"). "BaseHTTPRequestHandler" provides a number of
   class and instance variables, and methods for use by subclasses.

   The handler will parse the request and the headers, then call a
   method specific to the request type. The method name is constructed
   from the request. For example, for the request method "SPAM", the
   "do_SPAM()" method will be called with no arguments. All of the
   relevant information is stored in instance variables of the
   handler.  Subclasses should not need to override or extend the
   "__init__()" method.

   "BaseHTTPRequestHandler" has the following instance variables:

   client_address

      Contains a tuple of the form "(host, port)" referring to the
      client’s address.

   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 should be shut down.

   requestline

      Contains the string representation of the HTTP request line. The
      terminating CRLF is stripped. This attribute should be set by
      "handle_one_request()". If no valid request line was processed,
      it should be set to the empty string.

   command

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

   path

      Contains the request path. If the query component of the URL is
      present, then "path" includes the query. Using the terminology
      of **RFC 3986**, "path" here includes "hier-part" and the
      "query".

   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"
      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 5322** 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.

      Changed in version 3.6: This is an "io.BufferedIOBase" stream.

   "BaseHTTPRequestHandler" has the following attributes:

   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 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 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 example, the server can choose to send "417
      Expectation Failed" as a response header and "return False".

      Added in version 3.2.

   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:
      "1*xx*", "204 No Content", "205 Reset Content", "304 Not
      Modified".

      Changed in version 3.4: 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.

      Changed in version 3.3: 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.

      This method does not reject input containing CRLF sequences.

      Changed in version 3.2: 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 are not buffered and sent directly the output stream. If
      the *message* is not specified, the HTTP message corresponding
      the response *code*  is sent.

      This method does not reject *message* containing CRLF sequences.

      Added in version 3.2.

   end_headers()

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

      Changed in version 3.2: 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.

      Added in version 3.3.

   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.

      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.

      Changed in version 3.3: 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, extra_response_headers=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.

   Changed in version 3.7: Added the *directory* parameter.

   Changed in version 3.9: The *directory* parameter accepts a *path-
   like object*.

   Changed in version 3.15: Added *extra_response_headers* parameter.

   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.

   default_content_type

      Specifies the Content-Type header value sent when the MIME type
      cannot be guessed from the file extension of the requested URL.
      By default, it is set to "'application/octet-stream'".

      Added in version 3.15.

   index_pages

      Specifies the filenames that are treated as directory index
      pages.

      Defaults to "("index.html", "index.htm")".

      Added in version 3.12.

   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.

      Changed in version 3.9: This dictionary is no longer filled with
      the default system mappings, but only contains overrides.

   extra_response_headers

      A sequence of "(name, value)" pairs containing user-defined
      extra HTTP response headers to add to each successful HTTP
      status 200 response. These headers are not included in other
      status code responses.

      Headers that the server sends automatically such as "Content-
      Type" will not be overwritten by "extra_response_headers".

   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()

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

      If the request was mapped to a directory, the directory is
      checked for an index page as specified by "index_pages". 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 an "'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.

      The instance attribute "extra_response_headers" is a sequence of
      "(name, value)" pairs containing user-defined extra response
      headers.

      Then follows a blank line signifying the end of the headers, and
      then the contents of the file are output.

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

      Changed in version 3.7: Support of the "'If-Modified-Since'"
      header.

   list_directory(path)

      Helper to list the contents of *path* when no index page is
      present.

      This returns either a *file-like object* (which must be closed
      by the caller) or "None" to indicate an error, in which case the
      caller has nothing further to do. In either case, the headers
      are sent.

   guess_type(path)

      Guess the type of the file at the given *path*.

      This returns a string of the form "type/subtype", usable for a
      MIME Content-type header.

      The default implementation looks the file’s extension up in
      "extensions_map", falling back to "mimetypes.guess_file_type()"
      and then to "default_content_type".

      Changed in version 3.13: Add "mimetypes.guess_file_type()" as a
      fallback.

The "SimpleHTTPRequestHandler" class can be used to create a very
basic webserver serving files relative to the current directory as
follows:

   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()

"SimpleHTTPRequestHandler" can also be subclassed to enhance behavior,
such as using different index file names by overriding the class
attribute "index_pages".


Command-line interface
======================

"http.server" can also be invoked directly using the "-m" switch of
the interpreter.  The following example illustrates how to serve files
relative to the current directory:

   python -m http.server [OPTIONS] [port]

The following options are accepted:

port

   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

-b, --bind <address>

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

      python -m http.server --bind 127.0.0.1

   Added in version 3.4.

   Changed in version 3.8: Support IPv6 in the "--bind" option.

-d, --directory <dir>

   Specifies a directory to which it should serve the files. By
   default, the server uses the current directory. For example, the
   following command uses a specific directory:

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

   Added in version 3.7.

-p, --protocol <version>

   Specifies the HTTP version to which the server is conformant. By
   default, the server is conformant to HTTP/1.0. For example, the
   following command runs an HTTP/1.1 conformant server:

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

   Added in version 3.11.

--content-type <content_type>

   Specifies the default Content-Type HTTP header used when the MIME
   type cannot be guessed from the URL’s file extension. By default,
   the server uses "'application/octet-stream'":

      python -m http.server --content-type text/html

   Added in version 3.15.

--tls-cert

   Specifies a TLS certificate chain for HTTPS connections:

      python -m http.server --tls-cert fullchain.pem

   Added in version 3.14.

--tls-key

   Specifies a private key file for HTTPS connections.

   This option requires "--tls-cert" to be specified.

   Added in version 3.14.

--tls-password-file

   Specifies the password file for password-protected private keys:

      python -m http.server \
             --tls-cert cert.pem \
             --tls-key key.pem \
             --tls-password-file password.txt

   This option requires "--tls-cert" to be specified.

   Added in version 3.14.

-H, --header <header> <value>

   Specify an additional HTTP Response Header to send on successful
   HTTP 200 responses. Can be used multiple times to send additional
   custom response headers. Headers that are sent automatically by the
   server (for instance Content-Type) will not be overwritten by the
   server.

   Added in version 3.15.


Security considerations
=======================

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

Methods "BaseHTTPRequestHandler.send_header()" and
"BaseHTTPRequestHandler.send_response_only()" assume sanitized input
and do not perform input validation such as checking for the presence
of CRLF sequences. Untrusted input may result in HTTP header injection
attacks.

Earlier versions of Python did not scrub control characters from the
log messages emitted to stderr from "python -m http.server" or the
default "BaseHTTPRequestHandler" ".log_message" implementation. This
could allow remote clients connecting to your server to send nefarious
control codes to your terminal.

Changed in version 3.12: Control characters are scrubbed in stderr
logs.
