:mod:`usocket` -- socket module

.. module:: usocket
 :synopsis: socket module

|see_cpython_module| :mod:`python:socket`.

This module provides access to the BSD socket interface.

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. Note that depending on a :term:`MicroPython port`, socket module can be builtin or need to be installed from micropython-lib (as in the case of :term:`MicroPython Unix port`), and some ports still accept only numeric addresses in the tuple format, and require to use getaddrinfo function to resolve domain names.

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(). Availability of IPv6 support depends on a :term:`MicroPython port`.

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, af=0, type=0, proto=0, flags=0, /)

 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. Arguments
 *af*, *type*, and *proto* (which have the same meaning as for the `socket()` function)
 can be used to filter which kind of addresses are returned. If a parameter is not
 specified or zero, all combinations of addresses can be returned (requiring
 filtering on the user side).

 The resulting list of 5-tuples has the following structure::

 (family, type, proto, canonname, sockaddr)

 The following example shows how to connect to a given url::

 s = usocket.socket()
 # This assumes that if "type" is not specified, an address for
 # SOCK_STREAM will be returned, which may be not true
 s.connect(usocket.getaddrinfo('www.micropython.org', 80)[0][-1])

 Recommended use of filtering params::

 s = usocket.socket()
 # Guaranteed to return an address which can be connect'ed to for
 # stream operation.
 s.connect(usocket.getaddrinfo('www.micropython.org', 80, 0, SOCK_STREAM)[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
 the :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"\x7f0円0円1円")
 '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 :term:`MicroPython port`.

.. data:: SOCK_STREAM
 SOCK_DGRAM

 Socket types.

.. data:: IPPROTO_UDP
 IPPROTO_TCP

 IP protocol numbers. Availability depends on a particular :term:`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 :term:`MicroPython port`.

.. data:: usocket.SO_*

 Socket options (an argument to `setsockopt()`). The exact
 inventory depends on a :term:`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 :term:`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.

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