__connect_nonblock

static VALUE
sock_connect_nonblock(VALUE sock, VALUE addr, VALUE ex)
{
    VALUE rai;
    rb_io_t *fptr;
    int n;

    SockAddrStringValueWithAddrinfo(addr, rai);
    addr = rb_str_new4(addr);
    GetOpenFile(sock, fptr);
    rb_io_set_nonblock(fptr);
    n = connect(fptr->fd, (struct sockaddr*)RSTRING_PTR(addr), RSTRING_SOCKLEN(addr));
    if (n < 0) {
        int e = errno;
        if (e == EINPROGRESS) {
            if (ex == Qfalse) {
                return sym_wait_writable;
            }
            rb_readwrite_syserr_fail(RB_IO_WAIT_WRITABLE, e, "connect(2) would block");
        }
        if (e == EISCONN) {
            if (ex == Qfalse) {
                return INT2FIX(0);
            }
        }
        rsock_syserr_fail_raddrinfo_or_sockaddr(e, "connect(2)", addr, rai);
    }

    return INT2FIX(n);
}