sock = socket.socket(
    socket.AF_INET,
    socket.SOCK_STREAM | socket.SOCK_NONBLOCK)
will still create a non-blocking socket on OSes that support
SOCK_NONBLOCK, but sock.type will be set to
socket.SOCK_STREAM.
Changed in version 3.9: The CAN_J1939 protocol was added.
Changed in version 3.10: The IPPROTO_MPTCP protocol was added.
socket.socketpair([family[, type[, proto]]])¶
Build a pair of connected socket objects using the given address family, socket
type, and protocol number.  Address family, socket type, and protocol number are
as for the socket() function above. The default family is AF_UNIX
if defined on the platform; otherwise, the default is AF_INET.
The newly created sockets are non-inheritable.
Changed in version 3.2: The returned socket objects now support the whole socket API, rather
than a subset.
Changed in version 3.4: The returned sockets are now non-inheritable.
Changed in version 3.5: Windows support added.
socket.create_connection




    
(address, timeout=GLOBAL_DEFAULT, source_address=None, *, all_errors=False)¶
Connect to a TCP service listening on the internet address (a 2-tuple
(host, port)), and return the socket object.  This is a higher-level
function than socket.connect(): if host is a non-numeric hostname,
it will try to resolve it for both AF_INET and AF_INET6,
and then try to connect to all possible addresses in turn until a
connection succeeds.  This makes it easy to write clients that are
compatible to both IPv4 and IPv6.
Passing the optional timeout parameter will set the timeout on the
socket instance before attempting to connect.  If no timeout is
supplied, the global default timeout setting returned by
getdefaulttimeout() is used.
If supplied, source_address must be a 2-tuple (host, port) for the
socket to bind to as its source address before connecting.  If host or port
are ‘’ or 0 respectively the OS default behavior will be used.
When a connection cannot be created, an exception is raised. By default,
it is the exception from the last address in the list. If all_errors
is True, it is an ExceptionGroup containing the errors of all
attempts.
Changed in version 3.2: source_address was added.
Changed in version 3.11: all_errors was added.
socket.create_server(address, *, family=AF_INET, backlog=None, reuse_port=False, dualstack_ipv6=False)¶
Convenience function which creates a TCP socket bound to address (a 2-tuple
(host, port)) and returns the socket object.
family should be either AF_INET or AF_INET6.
backlog is the queue size passed to socket.listen(); if not specified
, a default reasonable value is chosen.
reuse_port dictates whether to set the SO_REUSEPORT socket option.
If dualstack_ipv6 is true, family is AF_INET6 and the platform
supports it the socket will be able to accept both IPv4 and IPv6 connections,
else it will raise ValueError. Most POSIX platforms and Windows are
supposed to support this functionality.
When this functionality is enabled the address returned by
socket.getpeername() when an IPv4 connection occurs will be an IPv6
address represented as an IPv4-mapped IPv6 address.
If dualstack_ipv6 is false it will explicitly disable this functionality
on platforms that enable it by default (e.g. Linux).
This parameter can be used in conjunction with has_dualstack_ipv6():
import socket
addr = ("", 8080)  # all interfaces, port 8080
if socket.has_dualstack_ipv6():
    s = socket.create_server(addr, family=socket.AF_INET6, dualstack_ipv6=True)
else:
    s = socket.create_server(addr)
On POSIX platforms the SO_REUSEADDR socket option is set in order to
immediately reuse previous sockets which were bound on the same address
and remained in TIME_WAIT state.
Added in version 3.8.
socket.has_dualstack_ipv6()¶
Return True if the platform supports creating a TCP socket which can
handle both IPv4 and IPv6 connections.
Added in version 3.8.
socket.fromfd(fd, family, type, proto=0)¶
Duplicate the file descriptor fd (an integer as returned by a file object’s
fileno() method) and build a socket object from the result.  Address
family, socket type and protocol number are as for the socket() function
above. The file descriptor should refer to a socket, but this is not checked —
subsequent operations on the object may fail if the file descriptor is invalid.
This function is rarely needed, but can be used to get or set socket options on
a socket passed to a program as standard input or output (such as a server
started by the Unix inet daemon).  The socket is assumed to be in blocking mode.
The newly created socket is non-inheritable.
Changed in version 3.4: The returned socket is now non-inheritable.
socket.fromshare(data)¶
Instantiate a socket from data obtained from the socket.share()
method.  The socket is assumed to be in blocking mode.
Availability: Windows.
Added in version 3.3.
socket.SocketType¶
This is a Python type object that represents the socket object type. It is the
same as type(socket(...)).
socket.close(fd)¶
Close a socket file descriptor. This is like os.close(), but for
sockets. On some platforms (most notably Windows) os.close()
does not work for socket file descriptors.
Added in version 3.7.
socket.getaddrinfo(host, port, family=AF_UNSPEC, type=0, proto=0, flags=0)¶
This function wraps the C function getaddrinfo of the underlying system.
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.
host is a domain name, a string representation of an IPv4/v6 address
or None. port is a string service name such as 'http', a numeric
port number or None.  By passing None as the value of host
and port, you can pass NULL to the underlying C API.
The family, type and proto arguments can be optionally specified
in order to provide options and limit the list of addresses returned.
Pass their default values (AF_UNSPEC, 0, and 0, respectively)
to not limit the results. See the note below for details.
The flags argument can be one or several of the AI_* constants,
and will influence how results are computed and returned.
For example, AI_NUMERICHOST will disable domain name resolution
and will raise an error if host is a domain name.
The function returns a list of 5-tuples with the following structure:
(family, type, proto, canonname, sockaddr)
In these tuples, family, type, proto are all integers and are
meant to be passed to the socket() function.  canonname will be
a string representing the canonical name of the host if
AI_CANONNAME is part of the flags argument; else canonname
will be empty.  sockaddr is a tuple describing a socket address, whose
format depends on the returned family (a (address, port) 2-tuple for
AF_INET, a (address, port, flowinfo, scope_id) 4-tuple for
AF_INET6), and is meant to be passed to the socket.connect()




    

method.
If you intend to use results from getaddrinfo() to create a socket
(rather than, for example, retrieve canonname),
consider limiting the results by type (e.g. SOCK_STREAM or
SOCK_DGRAM) and/or proto (e.g. IPPROTO_TCP or
IPPROTO_UDP) that your application can handle.
The behavior with default values of family, type, proto
and flags is system-specific.
Many systems (for example, most Linux configurations) will return a sorted
list of all matching addresses.
These addresses should generally be tried in order until a connection succeeds
(possibly tried in parallel, for example, using a Happy Eyeballs algorithm).
In these cases, limiting the type and/or proto can help eliminate
unsuccessful or unusable connection attempts.
Some systems will, however, only return a single address.
(For example, this was reported on Solaris and AIX configurations.)
On these systems, limiting the type and/or proto helps ensure that
this address is usable.
Raises an auditing event socket.getaddrinfo with arguments host, port, family, type, protocol.
The following example fetches address information for a hypothetical TCP
connection to example.org on port 80 (results may differ on your
system if IPv6 isn’t enabled):
>>> socket.getaddrinfo("example.org", 80, proto=socket.IPPROTO_TCP)
[(socket.AF_INET6, socket.SOCK_STREAM,
 6, '', ('2606:2800:220:1:248:1893:25c8:1946', 80, 0, 0)),
 (socket.AF_INET, socket.SOCK_STREAM,
 6, '', ('93.184.216.34', 80))]
Changed in version 3.2: parameters can now be passed using keyword arguments.
Changed in version 3.7: for IPv6 multicast addresses, string representing an address will not
contain %scope_id part.
socket.getfqdn([name])¶
Return a fully qualified domain name for name. If name is omitted or empty,
it is interpreted as the local host.  To find the fully qualified name, the
hostname returned by gethostbyaddr() is checked, followed by aliases for the
host, if available.  The first name which includes a period is selected.  In
case no fully qualified domain name is available and name was provided,
it is returned unchanged.  If name was empty or equal to '0.0.0.0',
the hostname from gethostname() is returned.
socket.gethostbyname(hostname)¶
Translate a host name to IPv4 address format.  The IPv4 address is returned as a
string, such as  '100.50.200.5'.  If the host name is an IPv4 address itself
it is returned unchanged.  See gethostbyname_ex() for a more complete
interface. gethostbyname() does not support IPv6 name resolution, and
getaddrinfo() should be used instead for IPv4/v6 dual stack support.
Raises an auditing event socket.gethostbyname with argument hostname.
Availability: not WASI.
socket.gethostbyname_ex(hostname)¶
Translate a host name to IPv4 address format, extended interface. Return a
3-tuple (hostname, aliaslist, ipaddrlist) where hostname is the host’s
primary host name, aliaslist is a (possibly
empty) list of alternative host names for the same address, and ipaddrlist is
a list of IPv4 addresses for the same interface on the same host (often but not
always a single address). gethostbyname_ex() does not support IPv6 name
resolution, and getaddrinfo() should be used instead for IPv4/v6 dual
stack support.
Raises an auditing event socket.gethostbyname with argument hostname.
Availability: not WASI.
socket.gethostname()¶
Return a string containing the hostname of the machine where  the Python
interpreter is currently executing.
Raises an auditing event socket.gethostname with no arguments.
Note: gethostname() doesn’t always return the fully qualified domain
name; use getfqdn() for that.
Availability: not WASI.
socket.gethostbyaddr(ip_address)¶
Return a 3-tuple (hostname, aliaslist, ipaddrlist) where hostname is the
primary host name responding to the given ip_address, aliaslist is a
(possibly empty) list of alternative host names for the same address, and
ipaddrlist is a list of IPv4/v6 addresses for the same interface on the same
host (most likely containing only a single address). To find the fully qualified
domain name, use the function getfqdn(). gethostbyaddr() supports
both IPv4 and IPv6.
Raises an auditing event socket.gethostbyaddr with argument ip_address.
Availability: not WASI.
socket.getnameinfo(sockaddr, flags)¶
Translate a socket address sockaddr into a 2-tuple (host, port). Depending
on the settings of flags, the result can contain a fully qualified domain name
or numeric address representation in host.  Similarly, port can contain a
string port name or a numeric port number.
For IPv6 addresses, %scope_id is appended to the host part if sockaddr
contains meaningful scope_id. Usually this happens for multicast addresses.
For more information about flags you can consult getnameinfo(3).
Raises an auditing event socket.getnameinfo with argument sockaddr.
Availability: not WASI.
socket.getprotobyname(protocolname)¶
Translate an internet protocol name (for example, 'icmp') to a constant
suitable for passing as the (optional) third argument to the socket()
function.  This is usually only needed for sockets opened in “raw” mode
(SOCK_RAW); for the normal socket modes, the correct protocol is chosen
automatically if the protocol is omitted or zero.
Availability: not WASI.
socket.getservbyname(servicename[, protocolname])¶
Translate an internet service name and protocol name to a port number for that
service.  The optional protocol name, if given, should be 'tcp' or
'udp', otherwise any protocol will match.
Raises an auditing event socket.getservbyname with arguments servicename, protocolname.
Availability: not WASI.
socket.getservbyport(port[, protocolname])¶
Translate an internet port number and protocol name to a service name for that
service.  The optional protocol name, if given, should be 'tcp' or
'udp', otherwise any protocol will match.
Raises an auditing event socket.getservbyport with arguments port, protocolname.
Availability: not WASI.
socket.ntohl(x)¶
Convert 32-bit positive integers from network to host byte order.  On machines
where the host byte order is the same as network byte order, this is a no-op;
otherwise, it performs a 4-byte swap operation.
socket.ntohs(x)¶
Convert 16-bit positive integers from network to host byte order.  On machines
where the host byte order is the same as network byte order, this is a no-op;
otherwise, it performs a 2-byte swap operation.




    

Changed in version 3.10: Raises OverflowError if x does not fit in a 16-bit unsigned
integer.
socket.htonl(x)¶
Convert 32-bit positive integers from host to network byte order.  On machines
where the host byte order is the same as network byte order, this is a no-op;
otherwise, it performs a 4-byte swap operation.
socket.htons(x)¶
Convert 16-bit positive integers from host to network byte order.  On machines
where the host byte order is the same as network byte order, this is a no-op;
otherwise, it performs a 2-byte swap operation.
Changed in version 3.10: Raises OverflowError if x does not fit in a 16-bit unsigned
integer.
socket.inet_aton(ip_string)¶
Convert an IPv4 address from dotted-quad string format (for example,
‘123.45.67.89’) to 32-bit packed binary format, as a bytes object four characters in
length.  This is useful when conversing with a program that uses the standard C
library and needs objects of type in_addr, which is the C type
for the 32-bit packed binary this function returns.
inet_aton() also accepts strings with less than three dots; see the
Unix manual page inet(3) for details.
If the IPv4 address string passed to this function is invalid,
OSError will be raised. Note that exactly what is valid depends on
the underlying C implementation of inet_aton().
inet_aton() does not support IPv6, and inet_pton() should be used
instead for IPv4/v6 dual stack support.
socket.inet_ntoa(packed_ip)¶
Convert a 32-bit packed IPv4 address (a bytes-like object four
bytes in length) to its standard dotted-quad string representation (for example,
‘123.45.67.89’).  This is useful when conversing with a program that uses the
standard C library and needs objects of type in_addr, which
is the C type for the 32-bit packed binary data this function takes as an
argument.
If the byte sequence passed to this function is not exactly 4 bytes in
length, OSError will be raised. inet_ntoa() does not
support IPv6, and inet_ntop() should be used instead for IPv4/v6 dual
stack support.
Changed in version 3.5: Writable bytes-like object is now accepted.
socket.inet_pton(address_family, ip_string)¶
Convert an IP address from its family-specific string format to a packed,
binary format. inet_pton() is useful when a library or network protocol
calls for an object of type in_addr (similar to
inet_aton()) or in6_addr.
Supported values for address_family are currently AF_INET and
AF_INET6. If the IP address string ip_string is invalid,
OSError will be raised. Note that exactly what is valid depends on
both the value of address_family and the underlying implementation of
inet_pton().
Availability: Unix, Windows.
Changed in version 3.4: Windows support added
socket.inet_ntop(address_family, packed_ip)¶
Convert a packed IP address (a bytes-like object of some number of
bytes) to its standard, family-specific string representation (for
example, '7.10.0.5' or '5aef:2b::8').
inet_ntop() is useful when a library or network protocol returns an
object of type in_addr (similar to inet_ntoa()) or
in6_addr.
Supported values for address_family are currently AF_INET and
AF_INET6. If the bytes object packed_ip is not the correct
length for the specified address family, ValueError will be raised.
OSError is raised for errors from the call to inet_ntop().
Availability: Unix, Windows.
Changed in version 3.4: Windows support added
Changed in version 3.5: Writable bytes-like object is now accepted.
socket.CMSG_LEN(length)¶
Return the total length, without trailing padding, of an ancillary
data item with associated data of the given length.  This value
can often be used as the buffer size for recvmsg() to
receive a single item of ancillary data, but RFC 3542 requires
portable applications to use CMSG_SPACE() and thus include
space for padding, even when the item will be the last in the
buffer.  Raises OverflowError if length is outside the
permissible range of values.
Availability: Unix, not WASI.
Most Unix platforms.
Added in version 3.3.
socket.CMSG_SPACE(length)¶
Return the buffer size needed for recvmsg() to
receive an ancillary data item with associated data of the given
length, along with any trailing padding.  The buffer space needed
to receive multiple items is the sum of the CMSG_SPACE()
values for their associated data lengths.  Raises
OverflowError if length is outside the permissible range
of values.
Note that some systems might support ancillary data without
providing this function.  Also note that setting the buffer size
using the results of this function may not precisely limit the
amount of ancillary data that can be received, since additional
data may be able to fit into the padding area.
Availability: Unix, not WASI.
most Unix platforms.
Added in version 3.3.
socket.getdefaulttimeout()¶
Return the default timeout in seconds (float) for new socket objects. A value
of None indicates that new socket objects have no timeout. When the socket
module is first imported, the default is None.
socket.setdefaulttimeout(timeout)¶
Set the default timeout in seconds (float) for new socket objects.  When
the socket module is first imported, the default is None.  See
settimeout() for possible values and their respective
meanings.
socket.sethostname(name)¶
Set the machine’s hostname to name.  This will raise an
OSError if you don’t have enough rights.
Raises an auditing event socket.sethostname with argument name.
Availability: Unix, not Android.
Added in version 3.3.
socket.if_nameindex()¶
Return a list of network interface information
(index int, name string) tuples.
OSError if the system call fails.
Availability: Unix, Windows, not WASI.
Added in version 3.3.
Changed in version 3.8: Windows support was added.
On Windows network interfaces have different names in different contexts
(all names are examples):
UUID: {FB605B73-AAC2-49A6-9A2F-25416AEA0573}
name: ethernet_32770




    

friendly name: vEthernet (nat)
description: Hyper-V Virtual Ethernet Adapter
This function returns names of the second form from the list, ethernet_32770
in this example case.
socket.if_nametoindex(if_name)¶
Return a network interface index number corresponding to an
interface name.
OSError if no interface with the given name exists.
Availability: Unix, Windows, not WASI.
Added in version 3.3.
Changed in version 3.8: Windows support was added.
See also
“Interface name” is a name as documented in if_nameindex().
socket.if_indextoname(if_index)¶
Return a network interface name corresponding to an
interface index number.
OSError if no interface with the given index exists.
Availability: Unix, Windows, not WASI.
Added in version 3.3.
Changed in version 3.8: Windows support was added.
See also
“Interface name” is a name as documented in if_nameindex().
socket.send_fds(sock, buffers, fds[, flags[, address]])¶
Send the list of file descriptors fds over an AF_UNIX socket sock.
The fds parameter is a sequence of file descriptors.
Consult sendmsg() for the documentation of these parameters.
Availability: Unix, not WASI.
Unix platforms supporting sendmsg()
and SCM_RIGHTS mechanism.
Added in version 3.9.
socket.recv_fds(sock, bufsize, maxfds[, flags])¶
Receive up to maxfds file descriptors from an AF_UNIX socket sock.
Return (msg, list(fds), flags, addr).
Consult recvmsg() for the documentation of these parameters.
Availability: Unix, not WASI.
Unix platforms supporting recvmsg()
and SCM_RIGHTS mechanism.
Added in version 3.9.
Any truncated integers at the end of the list of file descriptors.
Socket Objects¶
Socket objects have the following methods.  Except for
makefile(), these correspond to Unix system calls applicable
to sockets.
Changed in version 3.2: Support for the context manager protocol was added.  Exiting the
context manager is equivalent to calling close().
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.
The newly created socket is non-inheritable.
Changed in version 3.4: The socket is now non-inheritable.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.bind(address)¶
Bind the socket to address.  The socket must not already be bound. (The format
of address depends on the address family — see above.)
Raises an auditing event socket.bind with arguments self, address.
Availability: not WASI.
socket.close()¶
Mark the socket closed.  The underlying system resource (e.g. a file
descriptor) is also closed when all file objects from makefile()
are closed.  Once that happens, all future operations on the socket
object will fail. The remote end will receive no more data (after
queued data is flushed).
Sockets are automatically closed when they are garbage-collected, but
it is recommended to close() them explicitly, or to use a
with statement around them.
Changed in version 3.6: OSError is now raised if an error occurs when the underlying
close() call is made.
close() releases the resource associated with a connection but
does not necessarily close the connection immediately.  If you want
to close the connection in a timely fashion, call shutdown()
before close().
socket.connect(address)¶
Connect to a remote socket at address. (The format of address depends on the
address family — see above.)
If the connection is interrupted by a signal, the method waits until the
connection completes, or raises a TimeoutError on timeout, if the
signal handler doesn’t raise an exception and the socket is blocking or has
a timeout. For non-blocking sockets, the method raises an
InterruptedError exception if the connection is interrupted by a
signal (or the exception raised by the signal handler).
Raises an auditing event socket.connect with arguments self, address.
Changed in version 3.5: The method now waits until the connection completes instead of raising an
InterruptedError exception if the connection is interrupted by a
signal, the signal handler doesn’t raise an exception and the socket is
blocking or has a timeout (see the PEP 475 for the rationale).
Availability: not WASI.
socket.connect_ex(address)¶
Like connect(address), but return an error indicator instead of raising an
exception for errors returned by the C-level connect() call (other
problems, such as “host not found,” can still raise exceptions).  The error
indicator is 0 if the operation succeeded, otherwise the value of the
errno variable.  This is useful to support, for example, asynchronous
connects.
Raises an auditing event socket.connect with arguments self, address.
Availability: not WASI.
socket.detach()¶
Put the socket object into closed state without actually closing the
underlying file descriptor.  The file descriptor is returned, and can
be reused for other purposes.
Added in version 3.2.
The newly created socket is non-inheritable.
Changed in version 3.4: The socket is now non-inheritable.
Availability: not WASI.
socket.fileno()¶
Return the socket’s file descriptor (a small integer), or -1 on failure. This
is useful with select.select().
Under Windows the small integer returned by this method cannot be used where a
file descriptor can be used (such as os.fdopen()




    
).  Unix does not have
this limitation.
socket.get_inheritable()¶
Get the inheritable flag of the socket’s file
descriptor or socket’s handle: True if the socket can be inherited in
child processes, False if it cannot.
Added in version 3.4.
socket.getpeername()¶
Return the remote address to which the socket is connected.  This is useful to
find out the port number of a remote IPv4/v6 socket, for instance. (The format
of the address returned depends on the address family — see above.)  On some
systems this function is not supported.
socket.getsockname()¶
Return the socket’s own address.  This is useful to find out the port number of
an IPv4/v6 socket, for instance. (The format of the address returned depends on
the address family — see above.)
socket.getsockopt(level, optname[, buflen])¶
Return the value of the given socket option (see the Unix man page
getsockopt(2)).  The needed symbolic constants (SO_* etc.)
are defined in this module.  If buflen is absent, an integer option is assumed
and its integer value is returned by the function.  If buflen is present, it
specifies the maximum length of the buffer used to receive the option in, and
this buffer is returned as a bytes object.  It is up to the caller to decode the
contents of the buffer (see the optional built-in module struct for a way
to decode C structures encoded as byte strings).
Availability: not WASI.
socket.getblocking()¶
Return True if socket is in blocking mode, False if in
non-blocking.
This is equivalent to checking socket.gettimeout() != 0.
Added in version 3.7.
socket.gettimeout()¶
Return the timeout in seconds (float) associated with socket operations,
or None if no timeout is set.  This reflects the last call to
setblocking() or settimeout().
socket.ioctl(control, option)¶
The ioctl() method is a limited interface to the WSAIoctl system
interface.  Please refer to the Win32 documentation for more
information.
On other platforms, the generic fcntl.fcntl() and fcntl.ioctl()
functions may be used; they accept a socket object as their first argument.
Currently only the following control codes are supported:
SIO_RCVALL, SIO_KEEPALIVE_VALS, and SIO_LOOPBACK_FAST_PATH.
Availability: Windows
Changed in version 3.6: SIO_LOOPBACK_FAST_PATH was added.
socket.listen([backlog])¶
Enable a server to accept connections.  If backlog is specified, it must
be at least 0 (if it is lower, it is set to 0); it specifies the number of
unaccepted connections that the system will allow before refusing new
connections. If not specified, a default reasonable value is chosen.
Availability: not WASI.
Changed in version 3.5: The backlog parameter is now optional.
socket.makefile(mode='r', buffering=None, *, encoding=None, errors=None, newline=None)¶
Return a file object associated with the socket.  The exact returned
type depends on the arguments given to makefile().  These arguments are
interpreted the same way as by the built-in open() function, except
the only supported mode values are 'r' (default), 'w', 'b', or
a combination of those.
The socket must be in blocking mode; it can have a timeout, but the file
object’s internal buffer may end up in an inconsistent state if a timeout
occurs.
Closing the file object returned by makefile() won’t close the
original socket unless all other file objects have been closed and
socket.close() has been called on the socket object.
On Windows, the file-like object created by makefile() cannot be
used where a file object with a file descriptor is expected, such as the
stream arguments of subprocess.Popen().
socket.recv(bufsize[, flags])¶
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. A returned empty bytes object indicates that the client has disconnected.
See the Unix manual page recv(2) for the meaning of the optional argument
flags; it defaults to zero.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.recvfrom(bufsize[, flags])¶
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 Unix manual page
recv(2) for the meaning of the optional argument flags; it defaults
to zero. (The format of address depends on the address family — see above.)
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
Changed in version 3.7: For multicast IPv6 address, first item of address does not contain
%scope_id part anymore. In order to get full IPv6 address use
getnameinfo().
socket.recvmsg(bufsize[, ancbufsize[, flags]])¶
Receive normal data (up to bufsize bytes) and ancillary data from
the socket.  The ancbufsize argument sets the size in bytes of
the internal buffer used to receive the ancillary data; it defaults
to 0, meaning that no ancillary data will be received.  Appropriate
buffer sizes for ancillary data can be calculated using
CMSG_SPACE() or CMSG_LEN(), and items which do not fit
into the buffer might be truncated or discarded.  The flags
argument defaults to 0 and has the same meaning as for
recv().
The return value is a 4-tuple: (data, ancdata, msg_flags,
address).  The data item is a bytes object holding the
non-ancillary data received.  The ancdata item is a list of zero
or more tuples (cmsg_level, cmsg_type, cmsg_data) representing
the ancillary data (control messages) received: cmsg_level and
cmsg_type are integers specifying the protocol level and
protocol-specific type respectively, and cmsg_data is a
bytes object holding the associated data.  The msg_flags
item is the bitwise OR of various flags indicating conditions on
the received message; see your system documentation for details.
If the receiving socket is unconnected, address is the address of
the sending socket, if available; otherwise, its value is
unspecified.




    

On some systems, sendmsg() and recvmsg() can be used to
pass file descriptors between processes over an AF_UNIX
socket.  When this facility is used (it is often restricted to
SOCK_STREAM sockets), recvmsg() will return, in its
ancillary data, items of the form (socket.SOL_SOCKET,
socket.SCM_RIGHTS, fds), where fds is a bytes object
representing the new file descriptors as a binary array of the
native C int type.  If recvmsg() raises an
exception after the system call returns, it will first attempt to
close any file descriptors received via this mechanism.
Some systems do not indicate the truncated length of ancillary data
items which have been only partially received.  If an item appears
to extend beyond the end of the buffer, recvmsg() will issue
a RuntimeWarning, and will return the part of it which is
inside the buffer provided it has not been truncated before the
start of its associated data.
On systems which support the SCM_RIGHTS mechanism, the
following function will receive up to maxfds file descriptors,
returning the message data and a list containing the descriptors
(while ignoring unexpected conditions such as unrelated control
messages being received).  See also sendmsg().
import socket, array
def recv_fds(sock, msglen, maxfds):
    fds = array.array("i")   # Array of ints
    msg, ancdata, flags, addr = sock.recvmsg(msglen, socket.CMSG_LEN(maxfds * fds.itemsize))
    for cmsg_level, cmsg_type, cmsg_data in ancdata:
        if cmsg_level == socket.SOL_SOCKET and cmsg_type == socket.SCM_RIGHTS:
            # Append data, ignoring any truncated integers at the end.
            fds.frombytes(cmsg_data[:len(cmsg_data) - (len(cmsg_data) % fds.itemsize)])
    return msg, list(fds)
Availability: Unix.
Most Unix platforms.
Added in version 3.3.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.recvmsg_into(buffers[, ancbufsize[, flags]])¶
Receive normal data and ancillary data from the socket, behaving as
recvmsg() would, but scatter the non-ancillary data into a
series of buffers instead of returning a new bytes object.  The
buffers argument must be an iterable of objects that export
writable buffers (e.g. bytearray objects); these will be
filled with successive chunks of the non-ancillary data until it
has all been written or there are no more buffers.  The operating
system may set a limit (sysconf() value SC_IOV_MAX)
on the number of buffers that can be used.  The ancbufsize and
flags arguments have the same meaning as for recvmsg().
The return value is a 4-tuple: (nbytes, ancdata, msg_flags,
address), where nbytes is the total number of bytes of
non-ancillary data written into the buffers, and ancdata,
msg_flags and address are the same as for recvmsg().
Example:
>>> import socket
>>> s1, s2 = socket.socketpair()
>>> b1 = bytearray(b'----')
>>> b2 = bytearray(b'0123456789')
>>> b3 = bytearray(b'--------------')
>>> s1.send(b'Mary had a little lamb')
>>> s2.recvmsg_into([b1, memoryview(b2)[2:9], b3])
(22, [], 0, None)
>>> [b1, b2, b3]
[bytearray(b'Mary'), bytearray(b'01 had a 9'), bytearray(b'little lamb---')]
Availability: Unix.
Most Unix platforms.
Added in version 3.3.
socket.recvfrom_into(buffer[, nbytes[, flags]])¶
Receive data from the socket, writing it into buffer instead of creating a
new bytestring.  The return value is a pair (nbytes, address) where nbytes is
the number of bytes received and address is the address of the socket sending
the data.  See the Unix manual page recv(2) for the meaning of the
optional argument flags; it defaults to zero.  (The format of address
depends on the address family — see above.)
socket.recv_into(buffer[, nbytes[, flags]])¶
Receive up to nbytes bytes from the socket, storing the data into a buffer
rather than creating a new bytestring.  If nbytes is not specified (or 0),
receive up to the size available in the given buffer.  Returns the number of
bytes received.  See the Unix manual page recv(2) for the meaning
of the optional argument flags; it defaults to zero.
socket.send(bytes[, flags])¶
Send data to the socket.  The socket must be connected to a remote socket.  The
optional flags argument has the same meaning as for recv() above.
Returns the number of bytes sent. Applications are responsible for checking that
all data has been sent; if only some of the data was transmitted, the
application needs to attempt delivery of the remaining data. For further
information on this topic, consult the Socket Programming HOWTO.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.sendall(bytes[, flags])¶
Send data to the socket.  The socket must be connected to a remote socket.  The
optional flags argument has the same meaning as for recv() above.
Unlike send(), this method continues to send data from bytes until
either all data has been sent or an error occurs.  None is returned on
success.  On error, an exception is raised, and there is no way to determine how
much data, if any, was successfully sent.
Changed in version 3.5: The socket timeout is no longer reset each time data is sent successfully.
The socket timeout is now the maximum total duration to send all data.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.sendto(bytes, flags




    
, address)
Send data to the socket.  The socket should not be connected to a remote socket,
since the destination socket is specified by address.  The optional flags
argument has the same meaning as for recv() above.  Return the number of
bytes sent. (The format of address depends on the address family — see
above.)
Raises an auditing event socket.sendto with arguments self, address.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.sendmsg(buffers[, ancdata[, flags[, address]]])¶
Send normal and ancillary data to the socket, gathering the
non-ancillary data from a series of buffers and concatenating it
into a single message.  The buffers argument specifies the
non-ancillary data as an iterable of
bytes-like objects
(e.g. bytes objects); the operating system may set a limit
(sysconf() value SC_IOV_MAX) on the number of buffers
that can be used.  The ancdata argument specifies the ancillary
data (control messages) as an iterable of zero or more tuples
(cmsg_level, cmsg_type, cmsg_data), where cmsg_level and
cmsg_type are integers specifying the protocol level and
protocol-specific type respectively, and cmsg_data is a
bytes-like object holding the associated data.  Note that
some systems (in particular, systems without CMSG_SPACE())
might support sending only one control message per call.  The
flags argument defaults to 0 and has the same meaning as for
send().  If address is supplied and not None, it sets a
destination address for the message.  The return value is the
number of bytes of non-ancillary data sent.
The following function sends the list of file descriptors fds
over an AF_UNIX socket, on systems which support the
SCM_RIGHTS mechanism.  See also recvmsg().
import socket, array
def send_fds(sock, msg, fds):
    return sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, array.array("i", fds))])
Availability: Unix, not WASI.
Most Unix platforms.
Raises an auditing event socket.sendmsg with arguments self, address.
Added in version 3.3.
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise
an exception, the method now retries the system call instead of raising
an InterruptedError exception (see PEP 475 for the rationale).
socket.sendmsg_afalg([msg, ]*, op[, iv[, assoclen[, flags]]])¶
Specialized version of sendmsg() for AF_ALG socket.
Set mode, IV, AEAD associated data length and flags for AF_ALG socket.
Availability: Linux >= 2.6.38.
Added in version 3.6.
socket.sendfile(file, offset=0, count=None)¶
Send a file until EOF is reached by using high-performance
os.sendfile and return the total number of bytes which were sent.
file must be a regular file object opened in binary mode. If
os.sendfile is not available (e.g. Windows) or file is not a
regular file send() will be used instead. offset tells from where to
start reading the file. If specified, count is the total number of bytes
to transmit as opposed to sending the file until EOF is reached. File
position is updated on return or also in case of error in which case
file.tell() can be used to figure out the number of
bytes which were sent. The socket must be of SOCK_STREAM type.
Non-blocking sockets are not supported.
Added in version 3.5.
socket.set_inheritable(inheritable)¶
Set the inheritable flag of the socket’s file
descriptor or socket’s handle.
Added in version 3.4.
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(0.0)
Changed in version 3.7: The method no longer applies SOCK_NONBLOCK flag on
socket.type.
socket.settimeout(value)¶
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 a
timeout 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.
For further information, please consult the notes on socket timeouts.
Changed in version 3.7: The method no longer toggles SOCK_NONBLOCK flag on
socket.type.
socket.setsockopt(level, optname, value: int | Buffer)¶
socket.setsockopt(level, optname, None, optlen: int)
Set the value of the given socket option (see the Unix manual page
setsockopt(2)).  The needed symbolic constants are defined in this
module (SO_* etc. <socket-unix-constants>).  The value can be an integer,
None or a bytes-like object representing a buffer. In the latter
case it is up to the caller to ensure that the bytestring contains the
proper bits (see the optional built-in module struct for a way to
encode C structures as bytestrings). When value is set to None




    
,
optlen argument is required. It’s equivalent to calling setsockopt() C
function with optval=NULL and optlen=optlen.
Changed in version 3.5: Writable bytes-like object is now accepted.
Changed in version 3.6: setsockopt(level, optname, None, optlen: int) form added.
Availability: not WASI.
socket.shutdown(how)¶
Shut down one or both halves of the connection.  If how is SHUT_RD,
further receives are disallowed.  If how is SHUT_WR, further sends
are disallowed.  If how is SHUT_RDWR, further sends and receives are
disallowed.
Availability: not WASI.
socket.share(process_id)¶
Duplicate a socket and prepare it for sharing with a target process.  The
target process must be provided with process_id.  The resulting bytes object
can then be passed to the target process using some form of interprocess
communication and the socket can be recreated there using fromshare().
Once this method has been called, it is safe to close the socket since
the operating system has already duplicated it for the target process.
Availability: Windows.
Added in version 3.3.
Note that there are no methods read() or write(); use
recv() and send() without flags argument instead.
Socket objects also have these (read-only) attributes that correspond to the
values given to the socket constructor.
socket.family¶
The socket family.
Notes on socket timeouts¶
A socket object can be in one of three modes: blocking, non-blocking, or
timeout.  Sockets are by default always created in blocking mode, but this
can be changed by calling setdefaulttimeout().
In blocking mode, operations block until complete or the system returns
an error (such as connection timed out).
In non-blocking mode, operations fail (with an error that is unfortunately
system-dependent) if they cannot be completed immediately: functions from the
select module can be used to know when and whether a socket is available
for reading or writing.
In timeout mode, operations fail if they cannot be completed within the
timeout specified for the socket (they raise a timeout exception)
or if the system returns an error.
At the operating system level, sockets in timeout mode are internally set
in non-blocking mode.  Also, the blocking and timeout modes are shared between
file descriptors and socket objects that refer to the same network endpoint.
This implementation detail can have visible consequences if e.g. you decide
to use the fileno() of a socket.
Timeouts and the connect method¶
The connect() operation is also subject to the timeout
setting, and in general it is recommended to call settimeout()
before calling connect() or pass a timeout parameter to
create_connection().  However, the system network stack may also
return a connection timeout error of its own regardless of any Python socket
timeout setting.
Timeouts and the accept method¶
If getdefaulttimeout() is not None, sockets returned by
the accept() method inherit that timeout.  Otherwise, the
behaviour depends on settings of the listening socket:
if the listening socket is in blocking mode or in timeout mode,
the socket returned by accept() is in blocking mode;
if the listening socket is in non-blocking mode, whether the socket
returned by accept() is in blocking or non-blocking mode
is operating system-dependent.  If you want to ensure cross-platform
behaviour, it is recommended you manually override this setting.
Example¶
Here are four minimal example programs using the TCP/IP protocol: a server that
echoes all data that it receives back (servicing only one client), and a client
using it.  Note that a server must perform the sequence socket(),
bind(), listen(), accept() (possibly
repeating the accept() to service more than one client), while a
client only needs the sequence socket(), connect().  Also
note that the server does not sendall()/recv() on
the socket it is listening on but on the new socket returned by
accept().
The first two examples support IPv4 only.
# Echo server program
import socket
HOST = ''                 # Symbolic name meaning all available interfaces
PORT = 50007              # Arbitrary non-privileged port
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen(1)
    conn, addr = s.accept()
    with conn:
        print('Connected by', addr)
        while True:
            data = conn.recv(1024)
            if not data: break
            conn.sendall(data)
# Echo client program
import socket
HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((HOST, PORT))
    s.sendall(b'Hello, world')
    data = s.recv(1024)
print('Received', repr(data))
The next two examples are identical to the above two, but support both IPv4 and
IPv6. The server side will listen to the first address family available (it
should listen to both instead). On most of IPv6-ready systems, IPv6 will take
precedence and the server may not accept IPv4 traffic. The client side will try
to connect to all the addresses returned as a result of the name resolution, and
sends traffic to the first one connected successfully.
# Echo server program
import socket
import sys
HOST = None               # Symbolic name meaning all available interfaces
PORT = 50007              # Arbitrary non-privileged port
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC,
                              socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
    af, socktype, proto, canonname, sa = res
    try:
        s = socket.socket(af, socktype, proto)
    except OSError as msg:
        s = None




    

        continue
    try:
        s.bind(sa)
        s.listen(1)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print('could not open socket')
    sys.exit(1)
conn, addr = s.accept()
with conn:
    print('Connected by', addr)
    while True:
        data = conn.recv(1024)
        if not data: break
        conn.send(data)
# Echo client program
import socket
import sys
HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM):
    af, socktype, proto, canonname, sa = res
    try:
        s = socket.socket(af, socktype, proto)
    except OSError as msg:
        s = None
        continue
    try:
        s.connect(sa)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print('could not open socket')
    sys.exit(1)
with s:
    s.sendall(b'Hello, world')
    data = s.recv(1024)
print('Received', repr(data))
The next example shows how to write a very simple network sniffer with raw
sockets on Windows. The example requires administrator privileges to modify
the interface:
import socket
# the public network interface
HOST = socket.gethostbyname(socket.gethostname())
# create a raw socket and bind it to the public interface
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP)
s.bind((HOST, 0))
# Include IP headers
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
# receive all packets
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
# receive a packet
print(s.recvfrom(65565))
# disabled promiscuous mode
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)
The next example shows how to use the socket interface to communicate to a CAN
network using the raw socket protocol. To use CAN with the broadcast
manager protocol instead, open a socket with:
socket.socket(socket.AF_CAN, socket.SOCK_DGRAM, socket.CAN_BCM)
After binding (CAN_RAW) or connecting (CAN_BCM) the socket, you
can use the socket.send() and socket.recv() operations (and
their counterparts) on the socket object as usual.
This last example might require special privileges:
import socket
import struct
# CAN frame packing/unpacking (see 'struct can_frame' in <linux/can.h>)
can_frame_fmt = "=IB3x8s"
can_frame_size = struct.calcsize(can_frame_fmt)
def build_can_frame(can_id, data):
    can_dlc = len(data)
    data = data.ljust(8, b'\x00')
    return struct.pack(can_frame_fmt, can_id, can_dlc, data)
def dissect_can_frame(frame):
    can_id, can_dlc, data = struct.unpack(can_frame_fmt, frame)
    return (can_id, can_dlc, data[:can_dlc])
# create a raw socket and bind it to the 'vcan0' interface
s = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
s.bind(('vcan0',))
while True:
    cf, addr = s.recvfrom(can_frame_size)
    print('Received: can_id=%x, can_dlc=%x, data=%s' % dissect_can_frame(cf))
    try:
        s.send(cf)
    except OSError:
        print('Error sending CAN frame')
    try:
        s.send(build_can_frame(0x01, b'\x01\x02\x03'))
    except OSError:
        print('Error sending CAN frame')
Running an example several times with too small delay between executions, could
lead to this error:
OSError: [Errno 98] Address already in use
This is because the previous execution has left the socket in a TIME_WAIT
state, and can’t be immediately reused.
There is a socket flag to set, in order to prevent this,
socket.SO_REUSEADDR:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
the SO_REUSEADDR flag tells the kernel to reuse a local socket in
TIME_WAIT state, without waiting for its natural timeout to expire.
See also
For an introduction to socket programming (in C), see the following papers:
An Introductory 4.3BSD Interprocess Communication Tutorial, by Stuart Sechrest
An Advanced 4.3BSD Interprocess Communication Tutorial, by Samuel J.  Leffler et
both in the UNIX Programmer’s Manual, Supplementary Documents 1 (sections
PS1:7 and PS1:8).  The platform-specific reference material for the various
socket-related system calls are also a valuable source of information on the
details of socket semantics.  For Unix, refer to the manual pages; for Windows,
see the WinSock (or Winsock 2) specification.  For IPv6-ready APIs, readers may
want to refer to RFC 3493 titled Basic Socket Interface Extensions for IPv6.
    This page is licensed under the Python Software Foundation License Version 2.
    Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License.
      See History and License for more information.