'Send a PORT command with the current host and the given
port number.'

def sendport(self, host, port):

    hbytes = host.split('.')
    pbytes = [repr((port // 256)), repr((port % 256))]
    bytes = (hbytes + pbytes)
    cmd = ('PORT    ' + ','.join(bytes))
    return self.voidcmd(cmd)
