354 lines
14 KiB
ReStructuredText
354 lines
14 KiB
ReStructuredText
******************************
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:mod:`socket` -- socket module
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******************************
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.. module:: socket
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:synopsis: socket module
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|see_cpython_module| :mod:`python:socket`.
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This module provides access to the BSD socket interface.
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.. admonition:: Difference to CPython
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:class: attention
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For efficiency and consistency, socket objects in MicroPython implement a `stream`
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(file-like) interface directly. In CPython, you need to convert a socket to
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a file-like object using `makefile()` method. This method is still supported
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by MicroPython (but is a no-op), so where compatibility with CPython matters,
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be sure to use it.
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Socket address format(s)
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------------------------
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The native socket address format of the ``socket`` module is an opaque data type
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returned by `getaddrinfo` function, which must be used to resolve textual address
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(including numeric addresses)::
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sockaddr = socket.getaddrinfo('www.micropython.org', 80)[0][-1]
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# You must use getaddrinfo() even for numeric addresses
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sockaddr = socket.getaddrinfo('127.0.0.1', 80)[0][-1]
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# Now you can use that address
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sock.connect(sockaddr)
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Using `getaddrinfo` is the most efficient (both in terms of memory and processing
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power) and portable way to work with addresses.
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However, ``socket`` module (note the difference with native MicroPython
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``socket`` module described here) provides CPython-compatible way to specify
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addresses using tuples, as described below. Note that depending on a
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:term:`MicroPython port`, ``socket`` module can be builtin or need to be
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installed from `micropython-lib` (as in the case of :term:`MicroPython Unix port`),
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and some ports still accept only numeric addresses in the tuple format,
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and require to use `getaddrinfo` function to resolve domain names.
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Summing up:
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* Always use `getaddrinfo` when writing portable applications.
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* Tuple addresses described below can be used as a shortcut for
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quick hacks and interactive use, if your port supports them.
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Tuple address format for ``socket`` module:
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* IPv4: *(ipv4_address, port)*, where *ipv4_address* is a string with
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dot-notation numeric IPv4 address, e.g. ``"8.8.8.8"``, and *port* is and
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integer port number in the range 1-65535. Note the domain names are not
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accepted as *ipv4_address*, they should be resolved first using
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`socket.getaddrinfo()`.
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* IPv6: *(ipv6_address, port, flowinfo, scopeid)*, where *ipv6_address*
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is a string with colon-notation numeric IPv6 address, e.g. ``"2001:db8::1"``,
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and *port* is an integer port number in the range 1-65535. *flowinfo*
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must be 0. *scopeid* is the interface scope identifier for link-local
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addresses. Note the domain names are not accepted as *ipv6_address*,
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they should be resolved first using `socket.getaddrinfo()`. Availability
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of IPv6 support depends on a :term:`MicroPython port`.
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Functions
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---------
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.. function:: getaddrinfo(host, port, af=0, type=0, proto=0, flags=0, /)
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Translate the host/port argument into a sequence of 5-tuples that contain all the
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necessary arguments for creating a socket connected to that service. Arguments
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*af*, *type*, and *proto* (which have the same meaning as for the `socket()` function)
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can be used to filter which kind of addresses are returned. If a parameter is not
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specified or zero, all combinations of addresses can be returned (requiring
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filtering on the user side).
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The resulting list of 5-tuples has the following structure::
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(family, type, proto, canonname, sockaddr)
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The following example shows how to connect to a given url::
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s = socket.socket()
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# This assumes that if "type" is not specified, an address for
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# SOCK_STREAM will be returned, which may be not true
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s.connect(socket.getaddrinfo('www.micropython.org', 80)[0][-1])
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Recommended use of filtering params::
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s = socket.socket()
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# Guaranteed to return an address which can be connect'ed to for
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# stream operation.
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s.connect(socket.getaddrinfo('www.micropython.org', 80, 0, SOCK_STREAM)[0][-1])
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.. admonition:: Difference to CPython
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:class: attention
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CPython raises a ``socket.gaierror`` exception (`OSError` subclass) in case
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of error in this function. MicroPython doesn't have ``socket.gaierror``
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and raises OSError directly. Note that error numbers of `getaddrinfo()`
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form a separate namespace and may not match error numbers from
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the :mod:`errno` module. To distinguish `getaddrinfo()` errors, they are
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represented by negative numbers, whereas standard system errors are
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positive numbers (error numbers are accessible using ``e.args[0]`` property
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from an exception object). The use of negative values is a provisional
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detail which may change in the future.
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.. function:: inet_ntop(af, bin_addr)
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Convert a binary network address *bin_addr* of the given address family *af*
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to a textual representation::
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>>> socket.inet_ntop(socket.AF_INET, b"\x7f\0\0\1")
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'127.0.0.1'
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.. function:: inet_pton(af, txt_addr)
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Convert a textual network address *txt_addr* of the given address family *af*
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to a binary representation::
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>>> socket.inet_pton(socket.AF_INET, "1.2.3.4")
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b'\x01\x02\x03\x04'
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Constants
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---------
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.. data:: AF_INET
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AF_INET6
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Address family types. Availability depends on a particular :term:`MicroPython port`.
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.. data:: SOCK_STREAM
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SOCK_DGRAM
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Socket types.
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.. data:: IPPROTO_UDP
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IPPROTO_TCP
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IP protocol numbers. Availability depends on a particular :term:`MicroPython port`.
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Note that you don't need to specify these in a call to `socket.socket()`,
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because `SOCK_STREAM` socket type automatically selects `IPPROTO_TCP`, and
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`SOCK_DGRAM` - `IPPROTO_UDP`. Thus, the only real use of these constants
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is as an argument to `setsockopt()`.
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.. data:: socket.SOL_*
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Socket option levels (an argument to `setsockopt()`). The exact
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inventory depends on a :term:`MicroPython port`.
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.. data:: socket.SO_*
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Socket options (an argument to `setsockopt()`). The exact
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inventory depends on a :term:`MicroPython port`.
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Constants specific to WiPy:
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.. data:: IPPROTO_SEC
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Special protocol value to create SSL-compatible socket.
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class socket
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============
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.. class:: socket(af=AF_INET, type=SOCK_STREAM, proto=IPPROTO_TCP, /)
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Create a new socket using the given address family, socket type and
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protocol number. Note that specifying *proto* in most cases is not
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required (and not recommended, as some MicroPython ports may omit
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``IPPROTO_*`` constants). Instead, *type* argument will select needed
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protocol automatically::
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# Create STREAM TCP socket
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socket(AF_INET, SOCK_STREAM)
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# Create DGRAM UDP socket
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socket(AF_INET, SOCK_DGRAM)
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Methods
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-------
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.. method:: socket.close()
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Mark the socket closed and release all resources. Once that happens, all future operations
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on the socket object will fail. The remote end will receive EOF indication if
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supported by protocol.
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Sockets are automatically closed when they are garbage-collected, but it is recommended
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to `close()` them explicitly as soon you finished working with them.
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.. method:: socket.bind(address)
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Bind the socket to *address*. The socket must not already be bound.
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.. method:: socket.listen([backlog])
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Enable a server to accept connections. If *backlog* is specified, it must be at least 0
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(if it's lower, it will be set to 0); and specifies the number of unaccepted connections
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that the system will allow before refusing new connections. If not specified, a default
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reasonable value is chosen.
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.. method:: socket.accept()
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Accept a connection. The socket must be bound to an address and listening for connections.
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The return value is a pair (conn, address) where conn is a new socket object usable to send
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and receive data on the connection, and address is the address bound to the socket on the
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other end of the connection.
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.. method:: socket.connect(address)
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Connect to a remote socket at *address*.
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.. method:: socket.send(bytes)
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Send data to the socket. The socket must be connected to a remote socket.
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Returns number of bytes sent, which may be smaller than the length of data
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("short write").
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.. method:: socket.sendall(bytes)
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Send all data to the socket. The socket must be connected to a remote socket.
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Unlike `send()`, this method will try to send all of data, by sending data
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chunk by chunk consecutively.
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The behaviour of this method on non-blocking sockets is undefined. Due to this,
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on MicroPython, it's recommended to use `write()` method instead, which
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has the same "no short writes" policy for blocking sockets, and will return
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number of bytes sent on non-blocking sockets.
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.. method:: socket.recv(bufsize)
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Receive data from the socket. The return value is a bytes object representing the data
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received. The maximum amount of data to be received at once is specified by bufsize.
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.. method:: socket.sendto(bytes, address)
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Send data to the socket. The socket should not be connected to a remote socket, since the
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destination socket is specified by *address*.
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.. method:: socket.recvfrom(bufsize)
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Receive data from the socket. The return value is a pair *(bytes, address)* where *bytes* is a
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bytes object representing the data received and *address* is the address of the socket sending
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the data.
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.. method:: socket.setsockopt(level, optname, value)
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Set the value of the given socket option. The needed symbolic constants are defined in the
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socket module (SO_* etc.). The *value* can be an integer or a bytes-like object representing
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a buffer.
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.. method:: socket.settimeout(value)
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**Note**: Not every port supports this method, see below.
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Set a timeout on blocking socket operations. The value argument can be a nonnegative floating
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point number expressing seconds, or None. If a non-zero value is given, subsequent socket operations
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will raise an `OSError` exception if the timeout period value has elapsed before the operation has
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completed. If zero is given, the socket is put in non-blocking mode. If None is given, the socket
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is put in blocking mode.
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Not every :term:`MicroPython port` supports this method. A more portable and
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generic solution is to use `select.poll` object. This allows to wait on
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multiple objects at the same time (and not just on sockets, but on generic
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`stream` objects which support polling). Example::
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# Instead of:
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s.settimeout(1.0) # time in seconds
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s.read(10) # may timeout
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# Use:
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poller = select.poll()
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poller.register(s, select.POLLIN)
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res = poller.poll(1000) # time in milliseconds
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if not res:
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# s is still not ready for input, i.e. operation timed out
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.. admonition:: Difference to CPython
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:class: attention
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CPython raises a ``socket.timeout`` exception in case of timeout,
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which is an `OSError` subclass. MicroPython raises an OSError directly
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instead. If you use ``except OSError:`` to catch the exception,
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your code will work both in MicroPython and CPython.
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.. method:: socket.setblocking(flag)
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Set blocking or non-blocking mode of the socket: if flag is false, the socket is set to non-blocking,
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else to blocking mode.
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This method is a shorthand for certain `settimeout()` calls:
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* ``sock.setblocking(True)`` is equivalent to ``sock.settimeout(None)``
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* ``sock.setblocking(False)`` is equivalent to ``sock.settimeout(0)``
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.. method:: socket.makefile(mode='rb', buffering=0, /)
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Return a file object associated with the socket. The exact returned type depends on the arguments
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given to makefile(). The support is limited to binary modes only ('rb', 'wb', and 'rwb').
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CPython's arguments: *encoding*, *errors* and *newline* are not supported.
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.. admonition:: Difference to CPython
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:class: attention
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As MicroPython doesn't support buffered streams, values of *buffering*
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parameter is ignored and treated as if it was 0 (unbuffered).
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.. admonition:: Difference to CPython
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:class: attention
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Closing the file object returned by makefile() WILL close the
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original socket as well.
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.. method:: socket.read([size])
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Read up to size bytes from the socket. Return a bytes object. If *size* is not given, it
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reads all data available from the socket until EOF; as such the method will not return until
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the socket is closed. This function tries to read as much data as
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requested (no "short reads"). This may be not possible with
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non-blocking socket though, and then less data will be returned.
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.. method:: socket.readinto(buf[, nbytes])
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Read bytes into the *buf*. If *nbytes* is specified then read at most
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that many bytes. Otherwise, read at most *len(buf)* bytes. Just as
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`read()`, this method follows "no short reads" policy.
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Return value: number of bytes read and stored into *buf*.
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.. method:: socket.readline()
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Read a line, ending in a newline character.
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Return value: the line read.
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.. method:: socket.write(buf)
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Write the buffer of bytes to the socket. This function will try to
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write all data to a socket (no "short writes"). This may be not possible
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with a non-blocking socket though, and returned value will be less than
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the length of *buf*.
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Return value: number of bytes written.
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.. exception:: socket.error
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MicroPython does NOT have this exception.
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.. admonition:: Difference to CPython
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:class: attention
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CPython used to have a ``socket.error`` exception which is now deprecated,
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and is an alias of `OSError`. In MicroPython, use `OSError` directly.
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