Fix tests on windows

    #[cfg(windows)]

    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {

        use std::os::windows::prelude::*;

        use libc;

        use ws2_32;

        let n = unsafe {

            libc::send(self.0.as_raw_socket(),

            ws2_32::send(self.0.as_raw_socket(),

                         buf.as_ptr() as *const _,

                         buf.len() as libc::c_int,

                         0)