How to transfer a file to ssh server in an ssh-connection made by paramiko?

Try this:

s = paramiko.SSHClient()
s.set_missing_host_key_policy(paramiko.AutoAddPolicy())
s.connect("xxx.xxx.xxx.xxx",22,username=xxx,password='',timeout=4)

sftp = s.open_sftp()
sftp.put('/home/me/file.ext', '/remote/home/file.ext')

Here is another example from https://www.programcreek.com/python/example/4561/paramiko.SSHClient

def copy_file(hostname, port, username, password, src, dst):
    client = paramiko.SSHClient()
    client.load_system_host_keys()
    print (" Connecting to %s \n with username=%s... \n" %(hostname,username))
    t = paramiko.Transport(hostname, port)
    t.connect(username=username,password=password)
    sftp = paramiko.SFTPClient.from_transport(t)
    print ("Copying file: %s to path: %s" %(src, dst))
    sftp.put(src, dst)
    sftp.close()
    t.close()