FM / library

/usr/share/doc/python3-docs/html/_sources/library/

/usr/share/doc/python3-docs/html/_sources/library

Name	Size	Mode	Actions
2to3.rst.txt	15898	0644	edit dl rm
abc.rst.txt	11805	0644	edit dl rm
aifc.rst.txt	7503	0644	edit dl rm
allos.rst.txt	678	0644	edit dl rm
archiving.rst.txt	440	0644	edit dl rm
argparse.rst.txt	77480	0644	edit dl rm
array.rst.txt	10812	0644	edit dl rm
ast.rst.txt	10159	0644	edit dl rm
asynchat.rst.txt	8528	0644	edit dl rm
asyncio-dev.rst.txt	13398	0644	edit dl rm
asyncio-eventloop.rst.txt	33701	0644	edit dl rm
asyncio-eventloops.rst.txt	7660	0644	edit dl rm
asyncio-protocol.rst.txt	25170	0644	edit dl rm
asyncio-queue.rst.txt	4328	0644	edit dl rm
asyncio-stream.rst.txt	14363	0644	edit dl rm
asyncio-subprocess.rst.txt	15544	0644	edit dl rm
asyncio-sync.rst.txt	9078	0644	edit dl rm
asyncio-task.rst.txt	25406	0644	edit dl rm
asyncio.rst.txt	2272	0644	edit dl rm
asyncore.rst.txt	13624	0644	edit dl rm
atexit.rst.txt	3669	0644	edit dl rm
audioop.rst.txt	10712	0644	edit dl rm
base64.rst.txt	10371	0644	edit dl rm
bdb.rst.txt	12985	0644	edit dl rm
binary.rst.txt	654	0644	edit dl rm
binascii.rst.txt	6539	0644	edit dl rm
binhex.rst.txt	1709	0644	edit dl rm
bisect.rst.txt	5398	0644	edit dl rm
builtins.rst.txt	1465	0644	edit dl rm
bz2.rst.txt	8825	0644	edit dl rm
calendar.rst.txt	10988	0644	edit dl rm
cgi.rst.txt	22650	0644	edit dl rm
cgitb.rst.txt	2918	0644	edit dl rm
chunk.rst.txt	5094	0644	edit dl rm
cmath.rst.txt	9326	0644	edit dl rm
cmd.rst.txt	13795	0644	edit dl rm
code.rst.txt	7817	0644	edit dl rm
codecs.rst.txt	75564	0644	edit dl rm
codeop.rst.txt	3021	0644	edit dl rm
collections.abc.rst.txt	12861	0644	edit dl rm
collections.rst.txt	46063	0644	edit dl rm
colorsys.rst.txt	1820	0644	edit dl rm
compileall.rst.txt	8975	0644	edit dl rm
concurrency.rst.txt	673	0644	edit dl rm
concurrent.futures.rst.txt	16910	0644	edit dl rm
concurrent.rst.txt	171	0644	edit dl rm
configparser.rst.txt	48756	0644	edit dl rm
constants.rst.txt	3331	0644	edit dl rm
contextlib.rst.txt	28175	0644	edit dl rm
copy.rst.txt	3378	0644	edit dl rm
copyreg.rst.txt	2182	0644	edit dl rm
crypt.rst.txt	5122	0644	edit dl rm
crypto.rst.txt	411	0644	edit dl rm
csv.rst.txt	19902	0644	edit dl rm
ctypes.rst.txt	88613	0644	edit dl rm
curses.ascii.rst.txt	8920	0644	edit dl rm
curses.panel.rst.txt	2764	0644	edit dl rm
curses.rst.txt	76397	0644	edit dl rm
custominterp.rst.txt	569	0644	edit dl rm
datatypes.rst.txt	751	0644	edit dl rm
datetime.rst.txt	90524	0644	edit dl rm
dbm.rst.txt	14293	0644	edit dl rm
debug.rst.txt	471	0644	edit dl rm
decimal.rst.txt	74869	0644	edit dl rm
development.rst.txt	704	0644	edit dl rm
difflib.rst.txt	29861	0644	edit dl rm
dis.rst.txt	32567	0644	edit dl rm
distribution.rst.txt	452	0644	edit dl rm
distutils.rst.txt	1974	0644	edit dl rm
doctest.rst.txt	71743	0644	edit dl rm
dummy_threading.rst.txt	784	0644	edit dl rm
email.charset.rst.txt	9293	0644	edit dl rm
email.compat32-message.rst.txt	33493	0644	edit dl rm
email.contentmanager.rst.txt	9112	0644	edit dl rm
email.encoders.rst.txt	2715	0644	edit dl rm
email.errors.rst.txt	4792	0644	edit dl rm
email.examples.rst.txt	1915	0644	edit dl rm
email.generator.rst.txt	13637	0644	edit dl rm
email.header.rst.txt	9188	0644	edit dl rm
email.headerregistry.rst.txt	17957	0644	edit dl rm
email.iterators.rst.txt	2795	0644	edit dl rm
email.message.rst.txt	33008	0644	edit dl rm
email.mime.rst.txt	11721	0644	edit dl rm
email.parser.rst.txt	14092	0644	edit dl rm
email.policy.rst.txt	27022	0644	edit dl rm
email.rst.txt	6785	0644	edit dl rm
email.util.rst.txt	9214	0644	edit dl rm
ensurepip.rst.txt	4987	0644	edit dl rm
enum.rst.txt	32751	0644	edit dl rm
errno.rst.txt	6811	0644	edit dl rm
exceptions.rst.txt	25570	0644	edit dl rm
faulthandler.rst.txt	6136	0644	edit dl rm
fcntl.rst.txt	7152	0644	edit dl rm
filecmp.rst.txt	5623	0644	edit dl rm
fileformats.rst.txt	287	0644	edit dl rm
fileinput.rst.txt	8051	0644	edit dl rm
filesys.rst.txt	961	0644	edit dl rm
fnmatch.rst.txt	3103	0644	edit dl rm
formatter.rst.txt	13242	0644	edit dl rm
fpectl.rst.txt	4180	0644	edit dl rm
fractions.rst.txt	6364	0644	edit dl rm
frameworks.rst.txt	391	0644	edit dl rm
ftplib.rst.txt	17552	0644	edit dl rm
functional.rst.txt	365	0644	edit dl rm
functions.rst.txt	71621	0644	edit dl rm
functools.rst.txt	18503	0644	edit dl rm
gc.rst.txt	9694	0644	edit dl rm
getopt.rst.txt	6557	0644	edit dl rm
getpass.rst.txt	1882	0644	edit dl rm
gettext.rst.txt	25588	0644	edit dl rm
glob.rst.txt	3508	0644	edit dl rm
grp.rst.txt	2417	0644	edit dl rm
gzip.rst.txt	8301	0644	edit dl rm
hashlib.rst.txt	26523	0644	edit dl rm
heapq.rst.txt	13402	0644	edit dl rm
hmac.rst.txt	4020	0644	edit dl rm
html.entities.rst.txt	1319	0644	edit dl rm
html.parser.rst.txt	11275	0644	edit dl rm
html.rst.txt	1304	0644	edit dl rm
http.client.rst.txt	18870	0644	edit dl rm
http.cookiejar.rst.txt	27832	0644	edit dl rm
http.cookies.rst.txt	8645	0644	edit dl rm
http.rst.txt	7096	0644	edit dl rm
http.server.rst.txt	17639	0644	edit dl rm
i18n.rst.txt	408	0644	edit dl rm
idle.rst.txt	25834	0644	edit dl rm
imaplib.rst.txt	20367	0644	edit dl rm
imghdr.rst.txt	2938	0644	edit dl rm
imp.rst.txt	15548	0644	edit dl rm
importlib.rst.txt	53563	0644	edit dl rm
index.rst.txt	2258	0644	edit dl rm
inspect.rst.txt	53928	0644	edit dl rm
internet.rst.txt	992	0644	edit dl rm
intro.rst.txt	2645	0644	edit dl rm
io.rst.txt	40328	0644	edit dl rm
ipaddress.rst.txt	32340	0644	edit dl rm
ipc.rst.txt	649	0644	edit dl rm
itertools.rst.txt	38459	0644	edit dl rm
json.rst.txt	27876	0644	edit dl rm
keyword.rst.txt	617	0644	edit dl rm
language.rst.txt	522	0644	edit dl rm
linecache.rst.txt	2408	0644	edit dl rm
locale.rst.txt	25470	0644	edit dl rm
logging.config.rst.txt	33886	0644	edit dl rm
logging.handlers.rst.txt	42497	0644	edit dl rm
logging.rst.txt	60479	0644	edit dl rm
lzma.rst.txt	17361	0644	edit dl rm
macpath.rst.txt	707	0644	edit dl rm
mailbox.rst.txt	63055	0644	edit dl rm
mailcap.rst.txt	3691	0644	edit dl rm
markup.rst.txt	679	0644	edit dl rm
marshal.rst.txt	4855	0644	edit dl rm
math.rst.txt	14375	0644	edit dl rm
mimetypes.rst.txt	9839	0644	edit dl rm
misc.rst.txt	247	0644	edit dl rm
mm.rst.txt	431	0644	edit dl rm
mmap.rst.txt	11232	0644	edit dl rm
modulefinder.rst.txt	3240	0644	edit dl rm
modules.rst.txt	355	0644	edit dl rm
msilib.rst.txt	18612	0644	edit dl rm
msvcrt.rst.txt	4392	0644	edit dl rm
multiprocessing.rst.txt	104494	0644	edit dl rm
netdata.rst.txt	339	0644	edit dl rm
netrc.rst.txt	3007	0644	edit dl rm
nis.rst.txt	1993	0644	edit dl rm
nntplib.rst.txt	21821	0644	edit dl rm
numbers.rst.txt	8089	0644	edit dl rm
numeric.rst.txt	696	0644	edit dl rm
operator.rst.txt	18989	0644	edit dl rm
optparse.rst.txt	76996	0644	edit dl rm
os.path.rst.txt	16419	0644	edit dl rm
os.rst.txt	137534	0644	edit dl rm
ossaudiodev.rst.txt	17845	0644	edit dl rm
othergui.rst.txt	2822	0644	edit dl rm
parser.rst.txt	15148	0644	edit dl rm
pathlib.rst.txt	30045	0644	edit dl rm
pdb.rst.txt	19454	0644	edit dl rm
persistence.rst.txt	591	0644	edit dl rm
pickle.rst.txt	37440	0644	edit dl rm
pickletools.rst.txt	3729	0644	edit dl rm
pipes.rst.txt	2557	0644	edit dl rm
pkgutil.rst.txt	8730	0644	edit dl rm
platform.rst.txt	9624	0644	edit dl rm
plistlib.rst.txt	7398	0644	edit dl rm
poplib.rst.txt	8197	0644	edit dl rm
posix.rst.txt	3694	0644	edit dl rm
pprint.rst.txt	14274	0644	edit dl rm
profile.rst.txt	27969	0644	edit dl rm
pty.rst.txt	3123	0644	edit dl rm
pwd.rst.txt	2739	0644	edit dl rm
pyclbr.rst.txt	3297	0644	edit dl rm
pydoc.rst.txt	4688	0644	edit dl rm
pyexpat.rst.txt	28620	0644	edit dl rm
python.rst.txt	475	0644	edit dl rm
py_compile.rst.txt	3851	0644	edit dl rm
queue.rst.txt	7268	0644	edit dl rm
quopri.rst.txt	2571	0644	edit dl rm
random.rst.txt	18503	0644	edit dl rm
re.rst.txt	64936	0644	edit dl rm
readline.rst.txt	11943	0644	edit dl rm
reprlib.rst.txt	5162	0644	edit dl rm
resource.rst.txt	12291	0644	edit dl rm
rlcompleter.rst.txt	2294	0644	edit dl rm
runpy.rst.txt	8285	0644	edit dl rm
sched.rst.txt	4842	0644	edit dl rm
secrets.rst.txt	5930	0644	edit dl rm
select.rst.txt	28175	0644	edit dl rm
selectors.rst.txt	8925	0644	edit dl rm
shelve.rst.txt	8390	0644	edit dl rm
shlex.rst.txt	16441	0644	edit dl rm
shutil.rst.txt	26014	0644	edit dl rm
signal.rst.txt	17218	0644	edit dl rm
site.rst.txt	9628	0644	edit dl rm
smtpd.rst.txt	10806	0644	edit dl rm
smtplib.rst.txt	23439	0644	edit dl rm
sndhdr.rst.txt	1994	0644	edit dl rm
socket.rst.txt	68202	0644	edit dl rm
socketserver.rst.txt	23712	0644	edit dl rm
spwd.rst.txt	2958	0644	edit dl rm
sqlite3.rst.txt	39215	0644	edit dl rm
ssl.rst.txt	96021	0644	edit dl rm
stat.rst.txt	9805	0644	edit dl rm
statistics.rst.txt	15301	0644	edit dl rm
stdtypes.rst.txt	179240	0644	edit dl rm
string.rst.txt	35374	0644	edit dl rm
stringprep.rst.txt	4279	0644	edit dl rm
struct.rst.txt	19581	0644	edit dl rm
subprocess.rst.txt	45793	0644	edit dl rm
sunau.rst.txt	7390	0644	edit dl rm
superseded.rst.txt	258	0644	edit dl rm
symbol.rst.txt	975	0644	edit dl rm
symtable.rst.txt	4964	0644	edit dl rm
sys.rst.txt	58273	0644	edit dl rm
sysconfig.rst.txt	8749	0644	edit dl rm
syslog.rst.txt	4302	0644	edit dl rm
tabnanny.rst.txt	2007	0644	edit dl rm
tarfile.rst.txt	31749	0644	edit dl rm
telnetlib.rst.txt	7899	0644	edit dl rm
tempfile.rst.txt	13857	0644	edit dl rm
termios.rst.txt	3751	0644	edit dl rm
test.rst.txt	25764	0644	edit dl rm
text.rst.txt	584	0644	edit dl rm
textwrap.rst.txt	10519	0644	edit dl rm
threading.rst.txt	39257	0644	edit dl rm
time.rst.txt	32967	0644	edit dl rm
timeit.rst.txt	13000	0644	edit dl rm
tk.rst.txt	1639	0644	edit dl rm
tkinter.rst.txt	33027	0644	edit dl rm
tkinter.scrolledtext.rst.txt	1255	0644	edit dl rm
tkinter.tix.rst.txt	22653	0644	edit dl rm
tkinter.ttk.rst.txt	58489	0644	edit dl rm
token.rst.txt	2607	0644	edit dl rm
tokenize.rst.txt	10002	0644	edit dl rm
trace.rst.txt	6914	0644	edit dl rm
traceback.rst.txt	17854	0644	edit dl rm
tracemalloc.rst.txt	22089	0644	edit dl rm
tty.rst.txt	1097	0644	edit dl rm
turtle.rst.txt	71221	0644	edit dl rm
types.rst.txt	9999	0644	edit dl rm
typing.rst.txt	34332	0644	edit dl rm
undoc.rst.txt	780	0644	edit dl rm
unicodedata.rst.txt	5762	0644	edit dl rm
unittest.mock-examples.rst.txt	46206	0644	edit dl rm
unittest.mock.rst.txt	85991	0644	edit dl rm
unittest.rst.txt	93304	0644	edit dl rm
unix.rst.txt	446	0644	edit dl rm
urllib.error.rst.txt	2199	0644	edit dl rm
urllib.parse.rst.txt	27332	0644	edit dl rm
urllib.request.rst.txt	59360	0644	edit dl rm
urllib.robotparser.rst.txt	2969	0644	edit dl rm
urllib.rst.txt	466	0644	edit dl rm
uu.rst.txt	2387	0644	edit dl rm
uuid.rst.txt	8760	0644	edit dl rm
venv.rst.txt	20621	0644	edit dl rm
warnings.rst.txt	20152	0644	edit dl rm
wave.rst.txt	6870	0644	edit dl rm
weakref.rst.txt	21328	0644	edit dl rm
webbrowser.rst.txt	9783	0644	edit dl rm
windows.rst.txt	272	0644	edit dl rm
winreg.rst.txt	24073	0644	edit dl rm
winsound.rst.txt	5134	0644	edit dl rm
wsgiref.rst.txt	33047	0644	edit dl rm
xdrlib.rst.txt	8078	0644	edit dl rm
xml.dom.minidom.rst.txt	10198	0644	edit dl rm
xml.dom.pulldom.rst.txt	5186	0644	edit dl rm
xml.dom.rst.txt	39507	0644	edit dl rm
xml.etree.elementtree.rst.txt	43871	0644	edit dl rm
xml.rst.txt	6071	0644	edit dl rm
xml.sax.handler.rst.txt	15399	0644	edit dl rm
xml.sax.reader.rst.txt	12133	0644	edit dl rm
xml.sax.rst.txt	7159	0644	edit dl rm
xml.sax.utils.rst.txt	3901	0644	edit dl rm
xmlrpc.client.rst.txt	23071	0644	edit dl rm
xmlrpc.rst.txt	475	0644	edit dl rm
xmlrpc.server.rst.txt	14990	0644	edit dl rm
zipapp.rst.txt	17392	0644	edit dl rm
zipfile.rst.txt	24005	0644	edit dl rm
zipimport.rst.txt	5805	0644	edit dl rm
zlib.rst.txt	13912	0644	edit dl rm
_dummy_thread.rst.txt	762	0644	edit dl rm
_thread.rst.txt	6886	0644	edit dl rm
__future__.rst.txt	5245	0644	edit dl rm
__main__.rst.txt	904	0644	edit dl rm

Edit: /usr/share/doc/python3-docs/html/_sources/library/socketserver.rst.txt (23712B)

:mod:`socketserver` --- A framework for network servers
=======================================================

.. module:: socketserver
   :synopsis: A framework for network servers.

**Source code:** :source:`Lib/socketserver.py`

--------------

The :mod:`socketserver` module simplifies the task of writing network servers.

There are four basic concrete server classes:

.. class:: TCPServer(server_address, RequestHandlerClass, bind_and_activate=True)

This uses the Internet TCP protocol, which provides for
   continuous streams of data between the client and server.
   If *bind_and_activate* is true, the constructor automatically attempts to
   invoke :meth:`~BaseServer.server_bind` and
   :meth:`~BaseServer.server_activate`.  The other parameters are passed to
   the :class:`BaseServer` base class.

.. class:: UDPServer(server_address, RequestHandlerClass, bind_and_activate=True)

This uses datagrams, which are discrete packets of information that may
   arrive out of order or be lost while in transit.  The parameters are
   the same as for :class:`TCPServer`.

.. class:: UnixStreamServer(server_address, RequestHandlerClass, bind_and_activate=True)
           UnixDatagramServer(server_address, RequestHandlerClass, bind_and_activate=True)

These more infrequently used classes are similar to the TCP and
   UDP classes, but use Unix domain sockets; they're not available on
   non-Unix platforms.  The parameters are the same as for
   :class:`TCPServer`.

These four classes process requests :dfn:`synchronously`; each request must be
completed before the next request can be started.  This isn't suitable if each
request takes a long time to complete, because it requires a lot of computation,
or because it returns a lot of data which the client is slow to process.  The
solution is to create a separate process or thread to handle each request; the
:class:`ForkingMixIn` and :class:`ThreadingMixIn` mix-in classes can be used to
support asynchronous behaviour.

Creating a server requires several steps.  First, you must create a request
handler class by subclassing the :class:`BaseRequestHandler` class and
overriding its :meth:`~BaseRequestHandler.handle` method;
this method will process incoming
requests.  Second, you must instantiate one of the server classes, passing it
the server's address and the request handler class. It is recommended to use
the server in a :keyword:`with` statement. Then call the
:meth:`~BaseServer.handle_request` or
:meth:`~BaseServer.serve_forever` method of the server object to
process one or many requests.  Finally, call :meth:`~BaseServer.server_close`
to close the socket (unless you used a :keyword:`with` statement).

When inheriting from :class:`ThreadingMixIn` for threaded connection behavior,
you should explicitly declare how you want your threads to behave on an abrupt
shutdown.  The :class:`ThreadingMixIn` class defines an attribute
*daemon_threads*, which indicates whether or not the server should wait for
thread termination.  You should set the flag explicitly if you would like
threads to behave autonomously; the default is :const:`False`, meaning that
Python will not exit until all threads created by :class:`ThreadingMixIn` have
exited.

Server classes have the same external methods and attributes, no matter what
network protocol they use.

Server Creation Notes
---------------------

There are five classes in an inheritance diagram, four of which represent
synchronous servers of four types::

+------------+
   | BaseServer |
   +------------+
         |
         v
   +-----------+        +------------------+
   | TCPServer |------->| UnixStreamServer |
   +-----------+        +------------------+
         |
         v
   +-----------+        +--------------------+
   | UDPServer |------->| UnixDatagramServer |
   +-----------+        +--------------------+

Note that :class:`UnixDatagramServer` derives from :class:`UDPServer`, not from
:class:`UnixStreamServer` --- the only difference between an IP and a Unix
stream server is the address family, which is simply repeated in both Unix
server classes.

.. class:: ForkingMixIn
           ThreadingMixIn

Forking and threading versions of each type of server can be created
   using these mix-in classes.  For instance, :class:`ThreadingUDPServer`
   is created as follows::

class ThreadingUDPServer(ThreadingMixIn, UDPServer):
          pass

The mix-in class comes first, since it overrides a method defined in
   :class:`UDPServer`.  Setting the various attributes also changes the
   behavior of the underlying server mechanism.

:class:`ForkingMixIn` and the Forking classes mentioned below are
   only available on POSIX platforms that support :func:`~os.fork`.

.. class:: ForkingTCPServer
           ForkingUDPServer
           ThreadingTCPServer
           ThreadingUDPServer

These classes are pre-defined using the mix-in classes.

To implement a service, you must derive a class from :class:`BaseRequestHandler`
and redefine its :meth:`~BaseRequestHandler.handle` method.
You can then run various versions of
the service by combining one of the server classes with your request handler
class.  The request handler class must be different for datagram or stream
services.  This can be hidden by using the handler subclasses
:class:`StreamRequestHandler` or :class:`DatagramRequestHandler`.

Of course, you still have to use your head!  For instance, it makes no sense to
use a forking server if the service contains state in memory that can be
modified by different requests, since the modifications in the child process
would never reach the initial state kept in the parent process and passed to
each child.  In this case, you can use a threading server, but you will probably
have to use locks to protect the integrity of the shared data.

On the other hand, if you are building an HTTP server where all data is stored
externally (for instance, in the file system), a synchronous class will
essentially render the service "deaf" while one request is being handled --
which may be for a very long time if a client is slow to receive all the data it
has requested.  Here a threading or forking server is appropriate.

In some cases, it may be appropriate to process part of a request synchronously,
but to finish processing in a forked child depending on the request data.  This
can be implemented by using a synchronous server and doing an explicit fork in
the request handler class :meth:`~BaseRequestHandler.handle` method.

Another approach to handling multiple simultaneous requests in an environment
that supports neither threads nor :func:`~os.fork` (or where these are too
expensive or inappropriate for the service) is to maintain an explicit table of
partially finished requests and to use :mod:`selectors` to decide which
request to work on next (or whether to handle a new incoming request).  This is
particularly important for stream services where each client can potentially be
connected for a long time (if threads or subprocesses cannot be used).  See
:mod:`asyncore` for another way to manage this.

.. XXX should data and methods be intermingled, or separate?
   how should the distinction between class and instance variables be drawn?

Server Objects
--------------

.. class:: BaseServer(server_address, RequestHandlerClass)

This is the superclass of all Server objects in the module.  It defines the
   interface, given below, but does not implement most of the methods, which is
   done in subclasses.  The two parameters are stored in the respective
   :attr:`server_address` and :attr:`RequestHandlerClass` attributes.

.. method:: fileno()

Return an integer file descriptor for the socket on which the server is
      listening.  This function is most commonly passed to :mod:`selectors`, to
      allow monitoring multiple servers in the same process.

.. method:: handle_request()

Process a single request.  This function calls the following methods in
      order: :meth:`get_request`, :meth:`verify_request`, and
      :meth:`process_request`.  If the user-provided
      :meth:`~BaseRequestHandler.handle` method of the
      handler class raises an exception, the server's :meth:`handle_error` method
      will be called.  If no request is received within :attr:`timeout`
      seconds, :meth:`handle_timeout` will be called and :meth:`handle_request`
      will return.

.. method:: serve_forever(poll_interval=0.5)

Handle requests until an explicit :meth:`shutdown` request.  Poll for
      shutdown every *poll_interval* seconds.
      Ignores the :attr:`timeout` attribute.  It
      also calls :meth:`service_actions`, which may be used by a subclass or mixin
      to provide actions specific to a given service.  For example, the
      :class:`ForkingMixIn` class uses :meth:`service_actions` to clean up zombie
      child processes.

.. versionchanged:: 3.3
         Added ``service_actions`` call to the ``serve_forever`` method.

.. method:: service_actions()

This is called in the :meth:`serve_forever` loop. This method can be
      overridden by subclasses or mixin classes to perform actions specific to
      a given service, such as cleanup actions.

.. versionadded:: 3.3

.. method:: shutdown()

Tell the :meth:`serve_forever` loop to stop and wait until it does.

.. method:: server_close()

Clean up the server. May be overridden.

.. attribute:: address_family

The family of protocols to which the server's socket belongs.
      Common examples are :const:`socket.AF_INET` and :const:`socket.AF_UNIX`.

.. attribute:: RequestHandlerClass

The user-provided request handler class; an instance of this class is created
      for each request.

.. attribute:: server_address

The address on which the server is listening.  The format of addresses varies
      depending on the protocol family;
      see the documentation for the :mod:`socket` module
      for details.  For Internet protocols, this is a tuple containing a string giving
      the address, and an integer port number: ``('127.0.0.1', 80)``, for example.

.. attribute:: socket

The socket object on which the server will listen for incoming requests.

The server classes support the following class variables:

.. XXX should class variables be covered before instance variables, or vice versa?

.. attribute:: allow_reuse_address

Whether the server will allow the reuse of an address.  This defaults to
      :const:`False`, and can be set in subclasses to change the policy.

.. attribute:: request_queue_size

The size of the request queue.  If it takes a long time to process a single
      request, any requests that arrive while the server is busy are placed into a
      queue, up to :attr:`request_queue_size` requests.  Once the queue is full,
      further requests from clients will get a "Connection denied" error.  The default
      value is usually 5, but this can be overridden by subclasses.

.. attribute:: socket_type

The type of socket used by the server; :const:`socket.SOCK_STREAM` and
      :const:`socket.SOCK_DGRAM` are two common values.

.. attribute:: timeout

Timeout duration, measured in seconds, or :const:`None` if no timeout is
      desired.  If :meth:`handle_request` receives no incoming requests within the
      timeout period, the :meth:`handle_timeout` method is called.

There are various server methods that can be overridden by subclasses of base
   server classes like :class:`TCPServer`; these methods aren't useful to external
   users of the server object.

.. XXX should the default implementations of these be documented, or should
      it be assumed that the user will look at socketserver.py?

.. method:: finish_request(request, client_address)

Actually processes the request by instantiating :attr:`RequestHandlerClass` and
      calling its :meth:`~BaseRequestHandler.handle` method.

.. method:: get_request()

Must accept a request from the socket, and return a 2-tuple containing the *new*
      socket object to be used to communicate with the client, and the client's
      address.

.. method:: handle_error(request, client_address)

This function is called if the :meth:`~BaseRequestHandler.handle`
      method of a :attr:`RequestHandlerClass` instance raises
      an exception.  The default action is to print the traceback to
      standard error and continue handling further requests.

.. versionchanged:: 3.6
         Now only called for exceptions derived from the :exc:`Exception`
         class.

.. method:: handle_timeout()

This function is called when the :attr:`timeout` attribute has been set to a
      value other than :const:`None` and the timeout period has passed with no
      requests being received.  The default action for forking servers is
      to collect the status of any child processes that have exited, while
      in threading servers this method does nothing.

.. method:: process_request(request, client_address)

Calls :meth:`finish_request` to create an instance of the
      :attr:`RequestHandlerClass`.  If desired, this function can create a new process
      or thread to handle the request; the :class:`ForkingMixIn` and
      :class:`ThreadingMixIn` classes do this.

.. Is there any point in documenting the following two functions?
      What would the purpose of overriding them be: initializing server
      instance variables, adding new network families?

.. method:: server_activate()

Called by the server's constructor to activate the server.  The default behavior
      for a TCP server just invokes :meth:`~socket.socket.listen`
      on the server's socket.  May be overridden.

.. method:: server_bind()

Called by the server's constructor to bind the socket to the desired address.
      May be overridden.

.. method:: verify_request(request, client_address)

Must return a Boolean value; if the value is :const:`True`, the request will
      be processed, and if it's :const:`False`, the request will be denied.  This
      function can be overridden to implement access controls for a server. The
      default implementation always returns :const:`True`.

.. versionchanged:: 3.6
      Support for the :term:`context manager` protocol was added.  Exiting the
      context manager is equivalent to calling :meth:`server_close`.

Request Handler Objects
-----------------------

.. class:: BaseRequestHandler

This is the superclass of all request handler objects.  It defines
   the interface, given below.  A concrete request handler subclass must
   define a new :meth:`handle` method, and can override any of
   the other methods.  A new instance of the subclass is created for each
   request.

.. method:: setup()

Called before the :meth:`handle` method to perform any initialization actions
      required.  The default implementation does nothing.

.. method:: handle()

This function must do all the work required to service a request.  The
      default implementation does nothing.  Several instance attributes are
      available to it; the request is available as :attr:`self.request`; the client
      address as :attr:`self.client_address`; and the server instance as
      :attr:`self.server`, in case it needs access to per-server information.

The type of :attr:`self.request` is different for datagram or stream
      services.  For stream services, :attr:`self.request` is a socket object; for
      datagram services, :attr:`self.request` is a pair of string and socket.

.. method:: finish()

Called after the :meth:`handle` method to perform any clean-up actions
      required.  The default implementation does nothing.  If :meth:`setup`
      raises an exception, this function will not be called.

.. class:: StreamRequestHandler
           DatagramRequestHandler

These :class:`BaseRequestHandler` subclasses override the
   :meth:`~BaseRequestHandler.setup` and :meth:`~BaseRequestHandler.finish`
   methods, and provide :attr:`self.rfile` and :attr:`self.wfile` attributes.
   The :attr:`self.rfile` and :attr:`self.wfile` attributes can be
   read or written, respectively, to get the request data or return data
   to the client.

The :attr:`rfile` attributes of both classes support the
   :class:`io.BufferedIOBase` readable interface, and
   :attr:`DatagramRequestHandler.wfile` supports the
   :class:`io.BufferedIOBase` writable interface.

.. versionchanged:: 3.6
      :attr:`StreamRequestHandler.wfile` also supports the
      :class:`io.BufferedIOBase` writable interface.

Examples
--------

:class:`socketserver.TCPServer` Example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the server side::

import socketserver

class MyTCPHandler(socketserver.BaseRequestHandler):
       """
       The request handler class for our server.

It is instantiated once per connection to the server, and must
       override the handle() method to implement communication to the
       client.
       """

def handle(self):
           # self.request is the TCP socket connected to the client
           self.data = self.request.recv(1024).strip()
           print("{} wrote:".format(self.client_address[0]))
           print(self.data)
           # just send back the same data, but upper-cased
           self.request.sendall(self.data.upper())

if __name__ == "__main__":
       HOST, PORT = "localhost", 9999

# Create the server, binding to localhost on port 9999
       with socketserver.TCPServer((HOST, PORT), MyTCPHandler) as server:
           # Activate the server; this will keep running until you
           # interrupt the program with Ctrl-C
           server.serve_forever()

An alternative request handler class that makes use of streams (file-like
objects that simplify communication by providing the standard file interface)::

class MyTCPHandler(socketserver.StreamRequestHandler):

def handle(self):
           # self.rfile is a file-like object created by the handler;
           # we can now use e.g. readline() instead of raw recv() calls
           self.data = self.rfile.readline().strip()
           print("{} wrote:".format(self.client_address[0]))
           print(self.data)
           # Likewise, self.wfile is a file-like object used to write back
           # to the client
           self.wfile.write(self.data.upper())

The difference is that the ``readline()`` call in the second handler will call
``recv()`` multiple times until it encounters a newline character, while the
single ``recv()`` call in the first handler will just return what has been sent
from the client in one ``sendall()`` call.

This is the client side::

import socket
   import sys

HOST, PORT = "localhost", 9999
   data = " ".join(sys.argv[1:])

# Create a socket (SOCK_STREAM means a TCP socket)
   with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
       # Connect to server and send data
       sock.connect((HOST, PORT))
       sock.sendall(bytes(data + "\n", "utf-8"))

# Receive data from the server and shut down
       received = str(sock.recv(1024), "utf-8")

print("Sent:     {}".format(data))
   print("Received: {}".format(received))

The output of the example should look something like this:

Server:

.. code-block:: shell-session

$ python TCPServer.py
   127.0.0.1 wrote:
   b'hello world with TCP'
   127.0.0.1 wrote:
   b'python is nice'

Client:

.. code-block:: shell-session

$ python TCPClient.py hello world with TCP
   Sent:     hello world with TCP
   Received: HELLO WORLD WITH TCP
   $ python TCPClient.py python is nice
   Sent:     python is nice
   Received: PYTHON IS NICE

:class:`socketserver.UDPServer` Example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the server side::

import socketserver

class MyUDPHandler(socketserver.BaseRequestHandler):
       """
       This class works similar to the TCP handler class, except that
       self.request consists of a pair of data and client socket, and since
       there is no connection the client address must be given explicitly
       when sending data back via sendto().
       """

def handle(self):
           data = self.request[0].strip()
           socket = self.request[1]
           print("{} wrote:".format(self.client_address[0]))
           print(data)
           socket.sendto(data.upper(), self.client_address)

if __name__ == "__main__":
       HOST, PORT = "localhost", 9999
       with socketserver.UDPServer((HOST, PORT), MyUDPHandler) as server:
           server.serve_forever()

This is the client side::

import socket
   import sys

HOST, PORT = "localhost", 9999
   data = " ".join(sys.argv[1:])

# SOCK_DGRAM is the socket type to use for UDP sockets
   sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# As you can see, there is no connect() call; UDP has no connections.
   # Instead, data is directly sent to the recipient via sendto().
   sock.sendto(bytes(data + "\n", "utf-8"), (HOST, PORT))
   received = str(sock.recv(1024), "utf-8")

print("Sent:     {}".format(data))
   print("Received: {}".format(received))

The output of the example should look exactly like for the TCP server example.

Asynchronous Mixins
~~~~~~~~~~~~~~~~~~~

To build asynchronous handlers, use the :class:`ThreadingMixIn` and
:class:`ForkingMixIn` classes.

An example for the :class:`ThreadingMixIn` class::

import socket
   import threading
   import socketserver

class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler):

def handle(self):
           data = str(self.request.recv(1024), 'ascii')
           cur_thread = threading.current_thread()
           response = bytes("{}: {}".format(cur_thread.name, data), 'ascii')
           self.request.sendall(response)

class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer):
       pass

def client(ip, port, message):
       with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
           sock.connect((ip, port))
           sock.sendall(bytes(message, 'ascii'))
           response = str(sock.recv(1024), 'ascii')
           print("Received: {}".format(response))

if __name__ == "__main__":
       # Port 0 means to select an arbitrary unused port
       HOST, PORT = "localhost", 0

server = ThreadedTCPServer((HOST, PORT), ThreadedTCPRequestHandler)
       with server:
           ip, port = server.server_address

# Start a thread with the server -- that thread will then start one
           # more thread for each request
           server_thread = threading.Thread(target=server.serve_forever)
           # Exit the server thread when the main thread terminates
           server_thread.daemon = True
           server_thread.start()
           print("Server loop running in thread:", server_thread.name)

client(ip, port, "Hello World 1")
           client(ip, port, "Hello World 2")
           client(ip, port, "Hello World 3")

server.shutdown()

The output of the example should look something like this:

.. code-block:: shell-session

$ python ThreadedTCPServer.py
   Server loop running in thread: Thread-1
   Received: Thread-2: Hello World 1
   Received: Thread-3: Hello World 2
   Received: Thread-4: Hello World 3

The :class:`ForkingMixIn` class is used in the same way, except that the server
will spawn a new process for each request.
Available only on POSIX platforms that support :func:`~os.fork`.

cmd: