base_events.py 文件源码

def _check_resolved_address(sock, address):
    # Ensure that the address is already resolved to avoid the trap of hanging
    # the entire event loop when the address requires doing a DNS lookup.
    family = sock.family
    if family == socket.AF_INET:
        host, port = address
    elif family == socket.AF_INET6:
        host, port = address[:2]
    else:
        return

    type_mask = 0
    if hasattr(socket, 'SOCK_NONBLOCK'):
        type_mask |= socket.SOCK_NONBLOCK
    if hasattr(socket, 'SOCK_CLOEXEC'):
        type_mask |= socket.SOCK_CLOEXEC
    # Use getaddrinfo(flags=AI_NUMERICHOST) to ensure that the address is
    # already resolved.
    try:
        socket.getaddrinfo(host, port,
                           family=family,
                           type=(sock.type & ~type_mask),
                           proto=sock.proto,
                           flags=socket.AI_NUMERICHOST)
    except socket.gaierror as err:
        raise ValueError("address must be resolved (IP address), got %r: %s"
                         % (address, err))