cpython: 8b71cd67f548 (original) (raw)

--- a/Doc/library/socketserver.rst +++ b/Doc/library/socketserver.rst @@ -10,16 +10,34 @@ The :mod:socketserver module simplifies the task of writing network servers. -There are four basic server classes: :class:TCPServer uses the Internet TCP -protocol, which provides for continuous streams of data between the client and -server. :class:UDPServer uses datagrams, which are discrete packets of -information that may arrive out of order or be lost while in transit. The more -infrequently used :class:UnixStreamServer and :class:UnixDatagramServer -classes are similar, but use Unix domain sockets; they're not available on -non-Unix platforms. For more details on network programming, consult a book -such as -W. Richard Steven's UNIX Network Programming or Ralph Davis's Win32 Network -Programming. +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)[](#l1.38)

+

• 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 @@ -31,10 +49,12 @@ 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:handle method; this method will process incoming +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. Then call the -:meth:handle_request or :meth:serve_forever method of the server object to +: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. @@ -76,18 +96,33 @@ Note that :class:UnixDatagramServer de stream server is the address family, which is simply repeated in both Unix server classes. -Forking and threading versions of each type of server can be created using the -:class:ForkingMixIn and :class:ThreadingMixIn mix-in classes. For instance, -a threading UDP server class is created as follows:: + +.. class:: ForkingMixIn

•       ThreadingMixIn[](#l1.72)

+

• 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):[](#l1.78)

•      pass[](#l1.79)

• 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. +

-The mix-in class must come first, since it overrides a method defined in -:class:UDPServer. Setting the various attributes also change the -behavior of the underlying server mechanism. +.. class:: ForkingTCPServer

•       ForkingUDPServer[](#l1.91)

•       ThreadingTCPServer[](#l1.92)

•       ThreadingUDPServer[](#l1.93)

+

• 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:handle method. You can then run various versions of +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 @@ -109,7 +144,7 @@ has requested. Here a threading or fork 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:handle method. +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 @@ -127,227 +162,240 @@ connected for a long time (if threads or Server Objects -------------- -.. class:: BaseServer +.. 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.

• done in subclasses. The two parameters are stored in the respective
• :attr:server_address and :attr:RequestHandlerClass attributes.

-.. method:: BaseServer.fileno()

• .. 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.

•  Return an integer file descriptor for the socket on which the server is[](#l1.134)

•  listening.  This function is most commonly passed to :mod:`selectors`, to[](#l1.135)

•  allow monitoring multiple servers in the same process.[](#l1.136)

-.. method:: BaseServer.handle_request()

• .. 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: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:self.timeout
• seconds, :meth:handle_timeout will be called and :meth:handle_request
• will return.

•  Process a single request.  This function calls the following methods in[](#l1.149)

•  order: :meth:`get_request`, :meth:`verify_request`, and[](#l1.150)

•  :meth:`process_request`.  If the user-provided[](#l1.151)

•  :meth:`~BaseRequestHandler.handle` method of the[](#l1.152)

•  handler class raises an exception, the server's :meth:`handle_error` method[](#l1.153)

•  will be called.  If no request is received within :attr:`timeout`[](#l1.154)

•  seconds, :meth:`handle_timeout` will be called and :meth:`handle_request`[](#l1.155)

•  will return.[](#l1.156)

-.. method:: BaseServer.serve_forever(poll_interval=0.5)

• .. method:: serve_forever(poll_interval=0.5)

• Handle requests until an explicit :meth:shutdown request. Poll for
• shutdown every poll_interval seconds. Ignores :attr:self.timeout. 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.

•  Handle requests until an explicit :meth:`shutdown` request.  Poll for[](#l1.168)

•  shutdown every *poll_interval* seconds.[](#l1.169)

•  Ignores the :attr:`timeout` attribute.  It[](#l1.170)

•  also calls :meth:`service_actions`, which may be used by a subclass or mixin[](#l1.171)

•  to provide actions specific to a given service.  For example, the[](#l1.172)

•  :class:`ForkingMixIn` class uses :meth:`service_actions` to clean up zombie[](#l1.173)

•  child processes.[](#l1.174)

• .. versionchanged:: 3.3

•   Added ``service_actions`` call to the ``serve_forever`` method.[](#l1.177)

•  .. versionchanged:: 3.3[](#l1.178)

•     Added ``service_actions`` call to the ``serve_forever`` method.[](#l1.179)

-.. method:: BaseServer.service_actions()

• .. 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.

•  This is called in the :meth:`serve_forever` loop. This method can be[](#l1.188)

•  overridden by subclasses or mixin classes to perform actions specific to[](#l1.189)

•  a given service, such as cleanup actions.[](#l1.190)

+

•  .. versionadded:: 3.3[](#l1.192)

• .. versionadded:: 3.3

• .. method:: shutdown() +

•  Tell the :meth:`serve_forever` loop to stop and wait until it does.[](#l1.197)

-.. method:: BaseServer.shutdown()

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

• .. method:: server_close() +

•  Clean up the server. May be overridden.[](#l1.204)

-.. method:: BaseServer.server_close()

• .. attribute:: address_family

• Clean up the server. May be overridden. -
• .. versionadded:: 2.6

•  The family of protocols to which the server's socket belongs.[](#l1.213)

•  Common examples are :const:`socket.AF_INET` and :const:`socket.AF_UNIX`.[](#l1.214)

-.. attribute:: BaseServer.address_family

• .. attribute:: RequestHandlerClass

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

•  The user-provided request handler class; an instance of this class is created[](#l1.222)

•  for each request.[](#l1.223)

-.. attribute:: BaseServer.RequestHandlerClass

• .. attribute:: server_address

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

•  The address on which the server is listening.  The format of addresses varies[](#l1.231)

•  depending on the protocol family;[](#l1.232)

•  see the documentation for the :mod:`socket` module[](#l1.233)

•  for details.  For Internet protocols, this is a tuple containing a string giving[](#l1.234)

•  the address, and an integer port number: ``('127.0.0.1', 80)``, for example.[](#l1.235)

-.. attribute:: BaseServer.server_address

• .. attribute:: socket

• The address on which the server is listening. The format of addresses varies
• depending on the protocol family; see the documentation for the 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.

•  The socket object on which the server will listen for incoming requests.[](#l1.245)

-.. attribute:: BaseServer.socket

• The server classes support the following class variables: +
• .. XXX should class variables be covered before instance variables, or vice versa?

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

• .. attribute:: allow_reuse_address +

•  Whether the server will allow the reuse of an address.  This defaults to[](#l1.256)

•  :const:`False`, and can be set in subclasses to change the policy.[](#l1.257)

-The server classes support the following class variables: - -.. XXX should class variables be covered before instance variables, or vice versa?

• .. attribute:: request_queue_size

-.. attribute:: BaseServer.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.

•  The size of the request queue.  If it takes a long time to process a single[](#l1.269)

•  request, any requests that arrive while the server is busy are placed into a[](#l1.270)

•  queue, up to :attr:`request_queue_size` requests.  Once the queue is full,[](#l1.271)

•  further requests from clients will get a "Connection denied" error.  The default[](#l1.272)

•  value is usually 5, but this can be overridden by subclasses.[](#l1.273)

-.. attribute:: BaseServer.request_queue_size

• .. attribute:: socket_type

• 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.

•  The type of socket used by the server; :const:`socket.SOCK_STREAM` and[](#l1.284)

•  :const:`socket.SOCK_DGRAM` are two common values.[](#l1.285)

-.. attribute:: BaseServer.socket_type

• .. attribute:: timeout

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

•  Timeout duration, measured in seconds, or :const:`None` if no timeout is[](#l1.293)

•  desired.  If :meth:`handle_request` receives no incoming requests within the[](#l1.294)

•  timeout period, the :meth:`handle_timeout` method is called.[](#l1.295)

-.. attribute:: BaseServer.timeout

• 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.

• 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.

• .. XXX should the default implementations of these be documented, or should

•  it be assumed that the user will look at socketserver.py?[](#l1.307)

+

• .. method:: finish_request() +

•  Actually processes the request by instantiating :attr:`RequestHandlerClass` and[](#l1.311)

•  calling its :meth:`~BaseRequestHandler.handle` method.[](#l1.312)

-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.

• .. method:: get_request()

-.. XXX should the default implementations of these be documented, or should

• it be assumed that the user will look at socketserver.py? -

-.. method:: BaseServer.finish_request() -

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

•  Must accept a request from the socket, and return a 2-tuple containing the *new*[](#l1.327)

•  socket object to be used to communicate with the client, and the client's[](#l1.328)

•  address.[](#l1.329)

-.. method:: BaseServer.get_request()

• .. method:: handle_error(request, client_address)

• 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.

•  This function is called if the :meth:`~BaseRequestHandler.handle`[](#l1.338)

•  method of a :attr:`RequestHandlerClass` instance raises[](#l1.339)

•  an exception.  The default action is to print the traceback to[](#l1.340)

•  standard output and continue handling further requests.[](#l1.341)

-.. method:: BaseServer.handle_error(request, client_address)

• .. method:: handle_timeout()

• This function is called if the :attr:RequestHandlerClass's :meth:handle
• method raises an exception. The default action is to print the traceback to
• standard output and continue handling further requests.

•  This function is called when the :attr:`timeout` attribute has been set to a[](#l1.350)

•  value other than :const:`None` and the timeout period has passed with no[](#l1.351)

•  requests being received.  The default action for forking servers is[](#l1.352)

•  to collect the status of any child processes that have exited, while[](#l1.353)

•  in threading servers this method does nothing.[](#l1.354)

-.. method:: BaseServer.handle_timeout()

• .. method:: process_request(request, client_address)

• 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.

•  Calls :meth:`finish_request` to create an instance of the[](#l1.365)

•  :attr:`RequestHandlerClass`.  If desired, this function can create a new process[](#l1.366)

•  or thread to handle the request; the :class:`ForkingMixIn` and[](#l1.367)

•  :class:`ThreadingMixIn` classes do this.[](#l1.368)

-.. method:: BaseServer.process_request(request, client_address)

• .. Is there any point in documenting the following two functions?

•  What would the purpose of overriding them be: initializing server[](#l1.373)

•  instance variables, adding new network families?[](#l1.374)

• 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.

• .. method:: server_activate() +

•  Called by the server's constructor to activate the server.  The default behavior[](#l1.382)

•  for a TCP server just invokes :meth:`~socket.socket.listen`[](#l1.383)

•  on the server's socket.  May be overridden.[](#l1.384)

-.. 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_bind()

-.. method:: BaseServer.server_activate() -

• Called by the server's constructor to activate the server. The default behavior
• just :meth:listen\ s to the server's socket. May be overridden.

•  Called by the server's constructor to bind the socket to the desired address.[](#l1.396)

•  May be overridden.[](#l1.397)

-.. method:: BaseServer.server_bind()

• .. method:: verify_request(request, client_address)

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

•  Must return a Boolean value; if the value is :const:`True`, the request will[](#l1.405)

•  be processed, and if it's :const:`False`, the request will be denied.  This[](#l1.406)

•  function can be overridden to implement access controls for a server. The[](#l1.407)

•  default implementation always returns :const:`True`.[](#l1.408)

-.. method:: BaseServer.verify_request(request, client_address) +Request Handler Objects +----------------------- + +.. class:: BaseRequestHandler

• 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.

• 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.

-RequestHandler Objects ----------------------- - -The request handler class must define a new :meth:handle method, and can -override any of the following methods. A new instance is created for each -request.

• .. method:: setup()

- -.. method:: RequestHandler.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.

•  Called before the :meth:`handle` method to perform any initialization actions[](#l1.442)

•  required.  The default implementation does nothing.[](#l1.443)

-.. method:: RequestHandler.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.

• .. method:: handle()

• 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.
• However, this can be hidden by using the request handler subclasses
• :class:StreamRequestHandler or :class:DatagramRequestHandler, which
• override the :meth:setup and :meth:finish methods, and provide
• :attr:self.rfile and :attr:self.wfile attributes. :attr:self.rfile and
• :attr:self.wfile can be read or written, respectively, to get the request
• data or return data to the client.

•  This function must do all the work required to service a request.  The[](#l1.464)

•  default implementation does nothing.  Several instance attributes are[](#l1.465)

•  available to it; the request is available as :attr:`self.request`; the client[](#l1.466)

•  address as :attr:`self.client_address`; and the server instance as[](#l1.467)

•  :attr:`self.server`, in case it needs access to per-server information.[](#l1.468)

+

•  The type of :attr:`self.request` is different for datagram or stream[](#l1.470)

•  services.  For stream services, :attr:`self.request` is a socket object; for[](#l1.471)

•  datagram services, :attr:`self.request` is a pair of string and socket.[](#l1.472)

-.. method:: RequestHandler.setup()

• .. method:: finish() +

•  Called after the :meth:`handle` method to perform any clean-up actions[](#l1.478)

•  required.  The default implementation does nothing.  If :meth:`setup`[](#l1.479)

•  raises an exception, this function will not be called.[](#l1.480)

+

• Called before the :meth:handle method to perform any initialization actions
• required. The default implementation does nothing. +.. class:: StreamRequestHandler

•       DatagramRequestHandler[](#l1.486)

+

• 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.

Examples @@ -362,7 +410,7 @@ This is the server side:: class MyTCPHandler(socketserver.BaseRequestHandler): """

•   The RequestHandler class for our server.[](#l1.501)

•   The request handler class for our server.[](#l1.502)

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