:mod:`socket` --- socket module =============================== .. module:: socket :synopsis: socket module 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 :std:term:`stream` (file-like) interface directly. In CPython, you need to convert a socket to a file-like object using :meth:`~socket.socket.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 ``socket`` module is an opaque data type returned by :func:`getaddrinfo` function, which must be used to resolve textual address (including numeric addresses):: sockaddr = socket.getaddrinfo('www.micropython.org', 80)[0][-1] # You must use getaddrinfo() even for numeric addresses sockaddr = socket.getaddrinfo('127.0.0.1', 80)[0][-1] # Now you can use that address sock.connect(sockaddr) Using :func:`getaddrinfo` is the most efficient (both in terms of memory and processing power) and portable way to work with addresses. The ``socket`` module also provides a CPython-compatible way to specify addresses using tuples, as described below. On the OpenMV Cam the ``socket`` module is built in; numeric addresses may be given directly in the tuple format, but domain names must first be resolved with :func:`getaddrinfo`. Summing up: * Always use :func:`getaddrinfo` to resolve host names. * Tuple addresses described below can be used as a shortcut for numeric addresses, for quick hacks and interactive use. Tuple address format for the ``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 an integer port number in the range 1-65535. Domain names are not accepted as *ipv4_address*; resolve them first using :func:`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. Domain names are not accepted as *ipv6_address*; resolve them first using :func:`getaddrinfo`. Functions --------- .. function:: getaddrinfo(host: str, port: int, af: int = 0, type: int = 0, proto: int = 0, flags: int = 0, /) -> List[Tuple] 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 :class:`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 = socket.socket() # This assumes that if "type" is not specified, an address for # SOCK_STREAM will be returned, which may be not true s.connect(socket.getaddrinfo('www.micropython.org', 80)[0][-1]) Recommended use of filtering params:: s = socket.socket() # Guaranteed to return an address which can be connect'ed to for # stream operation. s.connect(socket.getaddrinfo('www.micropython.org', 80, 0, SOCK_STREAM)[0][-1]) .. admonition:: Difference to CPython :class: attention CPython raises a ``socket.gaierror`` exception (:exc:`OSError` subclass) in case of error in this function. MicroPython doesn't have ``socket.gaierror`` and raises OSError directly. Note that error numbers of :func:`getaddrinfo()` form a separate namespace and may not match error numbers from the :mod:`errno` module. To distinguish :func:`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: int, bin_addr: bytes) -> str Convert a binary network address *bin_addr* of the given address family *af* to a textual representation:: >>> socket.inet_ntop(socket.AF_INET, b"\x7f\0\0\1") '127.0.0.1' .. function:: inet_pton(af: int, txt_addr: str) -> bytes Convert a textual network address *txt_addr* of the given address family *af* to a binary representation:: >>> socket.inet_pton(socket.AF_INET, "1.2.3.4") b'\x01\x02\x03\x04' Constants --------- .. data:: AF_INET :type: int IPv4 address family. .. data:: AF_INET6 :type: int IPv6 address family. .. data:: SOCK_STREAM :type: int Stream (TCP) socket type. .. data:: SOCK_DGRAM :type: int Datagram (UDP) socket type. .. data:: SOCK_RAW :type: int Raw socket type. .. data:: IPPROTO_IP :type: int The IP protocol level. Used as the *level* argument to :meth:`~socket.socket.setsockopt` together with the ``IP_*`` options. .. data:: IPPROTO_TCP :type: int The TCP protocol. You do not need to pass this to :class:`socket` (the :data:`SOCK_STREAM` socket type selects it automatically); its only real use is as the *level* argument to :meth:`~socket.socket.setsockopt` together with the ``TCP_*`` options. .. data:: SOL_SOCKET :type: int The socket option level. Used as the *level* argument to :meth:`~socket.socket.setsockopt` together with the ``SO_*`` options. .. data:: SO_REUSEADDR :type: int Allow the socket to bind to an address/port that is still in the ``TIME_WAIT`` state. .. data:: SO_BROADCAST :type: int Permit sending datagrams to a broadcast address. .. data:: SO_KEEPALIVE :type: int Enable periodic transmission of keep-alive probes on a connected socket. .. data:: SO_SNDTIMEO :type: int Send timeout, in milliseconds, passed as the *value* argument to :meth:`~socket.socket.setsockopt`. .. data:: SO_RCVTIMEO :type: int Receive timeout, in milliseconds, passed as the *value* argument to :meth:`~socket.socket.setsockopt`. .. data:: IP_ADD_MEMBERSHIP :type: int Join a multicast group. An :data:`IPPROTO_IP`-level :meth:`~socket.socket.setsockopt` option. .. data:: IP_DROP_MEMBERSHIP :type: int Leave a multicast group. An :data:`IPPROTO_IP`-level :meth:`~socket.socket.setsockopt` option. .. data:: TCP_NODELAY :type: int Disable Nagle's algorithm. An :data:`IPPROTO_TCP`-level :meth:`~socket.socket.setsockopt` option. .. data:: MSG_PEEK :type: int For :meth:`~socket.socket.recv` / :meth:`~socket.socket.recvfrom`: return data without removing it from the input queue. .. data:: MSG_DONTWAIT :type: int For :meth:`~socket.socket.recv` / :meth:`~socket.socket.recvfrom`: perform the operation in non-blocking mode. Classes ------- .. class:: socket(af: int = AF_INET, type: int = SOCK_STREAM, proto: int = IPPROTO_TCP, /) Create a new socket using the given address family, socket type and protocol number. Specifying *proto* is in most cases not required (and not recommended); the *type* argument selects the needed protocol automatically:: # Create STREAM TCP socket socket(AF_INET, SOCK_STREAM) # Create DGRAM UDP socket socket(AF_INET, SOCK_DGRAM) .. method:: close() -> None 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 :meth:`close()` them explicitly as soon you finished working with them. .. method:: bind(address: Any) -> None Bind the socket to *address*. The socket must not already be bound. .. method:: listen(backlog: int = 2) -> None 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:: accept() -> Tuple["socket", Tuple] 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:: connect(address: Any) -> None Connect to a remote socket at *address*. .. method:: send(bytes: bytes) -> int 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:: sendall(bytes: bytes) -> None Send all data to the socket. The socket must be connected to a remote socket. Unlike :meth:`send()`, this method will try to send all of data, by sending data chunk by chunk consecutively. The behaviour of this method on non-blocking sockets is undefined. Due to this, on MicroPython, it's recommended to use :meth:`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:: recv(bufsize: int, flags: int = 0) -> bytes 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. The optional *flags* argument is a bitwise OR of message flags (:data:`MSG_PEEK`, :data:`MSG_DONTWAIT`), which have the same meaning as in CPython. .. method:: sendto(bytes: bytes, address: Any) -> int Send data to the socket. The socket should not be connected to a remote socket, since the destination socket is specified by *address*. .. method:: recvfrom(bufsize: int, flags: int = 0) -> Tuple[bytes, Tuple] 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. See the :meth:`recv` function for an explanation of the optional *flags* argument. .. method:: setsockopt(level: int, optname: int, value: Union[int, bytes]) -> None 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:: settimeout(value: Optional[float]) -> None 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 :exc:`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. A portable and generic alternative is to use a :class:`select.poll` object. This allows waiting on multiple objects at the same time (and not just on sockets, but on generic :std:term:`stream` objects which support polling). Example:: # Instead of: s.settimeout(1.0) # time in seconds s.read(10) # may timeout # Use: poller = select.poll() poller.register(s, select.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 :exc:`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:: setblocking(flag: bool) -> None 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 :meth:`settimeout()` calls: * ``sock.setblocking(True)`` is equivalent to ``sock.settimeout(None)`` * ``sock.setblocking(False)`` is equivalent to ``sock.settimeout(0)`` .. method:: makefile(mode: str = 'rb', buffering: int = 0, /) -> Any 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:: read(size: int | None = None) -> bytes 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:: readinto(buf: bytearray | memoryview, nbytes: int | None = None) -> int 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 :meth:`read()`, this method follows "no short reads" policy. Return value: number of bytes read and stored into *buf*. .. method:: readline() -> bytes Read a line, ending in a newline character. Return value: the line read. .. method:: write(buf: bytes) -> int 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. .. note:: MicroPython does not implement ``socket.error``. CPython has a deprecated ``socket.error`` exception that is an alias of :exc:`OSError`; in MicroPython, use :exc:`OSError` directly to catch socket-related errors.