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circuitpython/docs/library/usocket.rst

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