Lib/socket.py

Source:

cpython 3.14 @ ab2d84fe1023/Lib/socket.py ↗

Lib/socket.py is a Python wrapper around the _socket C extension. It re-exports all constants and the low-level socket class from _socket, then adds convenience functions (create_connection, create_server, getfqdn), context-manager support on socket, the makefile() bridge to io, and the socketpair helper.

Map

Lines	Symbol	Role
1-80	imports, re-exports	Import all from _socket; platform guards
81-200	socket subclass	Adds __enter__/__exit__, makefile, sendfile
201-350	create_connection	DNS lookup + connect with timeout and source_address
351-450	create_server	Convenience server socket with SO_REUSEADDR
451-600	getfqdn, gethostbyname_ex wrappers	DNS helpers
601-900	socketpair, fromfd, fromshare	Socket construction helpers

Reading

create_connection

create_connection(address, timeout, source_address) calls getaddrinfo to resolve the host, iterates the results, and tries each address family in turn, returning the first successfully connected socket. This handles IPv4/IPv6 dual-stack transparently.

# CPython: Lib/socket.py:201 create_connection
def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT,
                      source_address=None, *, all_errors=False):
    host, port = address
    exceptions = []
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
        af, socktype, proto, canonname, sa = res
        sock = socket(af, socktype, proto)
        try:
            sock.settimeout(timeout)
            if source_address:
                sock.bind(source_address)
            sock.connect(sa)
            exceptions.clear()
            return sock
        except error as exc:
            exceptions.append(exc)
            sock.close()
    ...

makefile() and the io bridge

socket.makefile(mode, buffering) wraps the socket's file descriptor in a FileIO, wraps that in a BufferedReader or BufferedWriter, and optionally wraps that in a TextIOWrapper. The closefd=False flag is used so the socket fd is not closed when the file object is garbage collected.

# CPython: Lib/socket.py:235 socket.makefile
def makefile(self, mode="r", buffering=None, *,
             encoding=None, errors=None, newline=None):
    for c in mode:
        if c not in {"r", "w", "b"}:
            raise ValueError("invalid mode %r" % mode)
    writing = "w" in mode
    reading = "r" in mode or not writing
    raw = SocketIO(self, mode)
    ...
    return io.TextIOWrapper(buffer, encoding, errors, newline)

create_server

create_server(address, *, family=AF_INET, backlog=None, reuse_port=False, dualstack_ipv6=False) creates a listening socket with SO_REUSEADDR set and calls bind + listen. The dualstack_ipv6 flag enables IPV6_V6ONLY=0 on platforms that support it.

gopy notes

Not yet ported. The planned package path is module/socket/. Go's net package provides net.Dial, net.Listen, and net.LookupHost which cover the same functionality. The makefile() bridge maps to wrapping a net.Conn in a bufio.ReadWriter.