Python 3.6.5 Documentation >  "http.server" — HTTP servers

"http.server" — HTTP servers
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**Source code:** Lib/http/server.py

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This module defines classes for implementing HTTP servers (Web
servers).

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.

The "HTTPServer" 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 (e.g. 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.

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 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.

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 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

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-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 a HTTP/1.1 compliant 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 chose to send "417
Expectation Failed" as a response header and "return False".

New 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:
"1xx", "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.

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 not buffered and sent directly the output stream.If the
*message* is not specified, the HTTP message corresponding the
response *code* is sent.

New 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.

New 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)

This class serves files from the current directory and below,
directly mapping the directory structure to HTTP requests.

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. The default is
signified by an empty string, and is considered to be
"application/octet-stream". The mapping is used case-
insensitively, and so should contain only lower-cased keys.

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 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 and the
contents are returned. Any "OSError" exception in opening the
requested file is mapped to a "404", "'File not found'" error.
Otherwise, the content type is guessed by calling the
"guess_type()" method, which in turn uses the *extensions_map*
variable.

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 invocation in the "http.server" module.

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 with a "port number" argument. Similar to the
previous example, this serves files relative to the current directory:

python -m http.server 8000

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

python -m http.server 8000 --bind 127.0.0.1

New in version 3.4: "--bind" 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".

Note: 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 8000