Modules/socketmodule.c

cpython 3.14 @ ab2d84fe1023/Modules/socketmodule.c ↗

Modules/socketmodule.c wraps the POSIX socket API for socket. It handles file- descriptor lifecycle, blocking/timeout mode, error-code translation, and address family portability across POSIX and Windows.

Map

Lines	Symbol	Role
1-500	PySocketSockObject struct, sock_new, sock_close	Socket object lifecycle
501-1200	sock_connect, sock_bind, sock_listen, sock_accept	Connection API
1201-2000	sock_recv, sock_recvfrom, sock_send, sock_sendto, sock_sendall	Data transfer
2001-2800	sock_setsockopt, sock_getsockopt	Socket options
2801-3500	sock_setblocking, sock_settimeout, sock_gettimeout	Blocking mode
3501-4500	getaddrinfo, getnameinfo	Name resolution
4501-6500	inet_pton, inet_ntop, htons/htonl, module constants	Address conversion

Reading

Blocking vs timeout mode

sock.setblocking(False) calls fcntl(fd, F_SETFL, O_NONBLOCK). sock.settimeout(t) puts the socket in non-blocking mode and stores t in so_timeout. All blocking operations (recv, send, connect, accept) implement their own select/poll loop when timeout is set, rather than using SO_RCVTIMEO/SO_SNDTIMEO.

// CPython: Modules/socketmodule.c:850 internal_connect
static int
internal_connect(PySocketSockObject *s, struct sockaddr *addr, int addrlen,
                 int raise)
{
    int res;
    Py_BEGIN_ALLOW_THREADS
    res = connect(s->sock_fd, addr, addrlen);
    Py_END_ALLOW_THREADS
    if (res != 0) {
        if (errno == EINPROGRESS && s->sock_timeout > 0) {
            /* wait until writable */
            ...
        }
    }
    return res;
}

sendall

sock.sendall(data) retries send in a loop until all bytes are sent or an error occurs. Partial sends (when the OS buffer is full) cause a retry with the remaining bytes.

Error mapping

POSIX errno values are translated to OSError subclasses (ConnectionRefusedError, TimeoutError, etc.) by set_error() which maps ECONNREFUSED, ETIMEDOUT, etc.

gopy notes

Not yet ported. module/socket/ is planned. The Go backend will use net.Conn from the Go standard library, which handles the timeout and non-blocking mode internally. The address family constants (AF_INET, AF_INET6, etc.) are module-level integers.