.. efun:: int tls_available()
  :experimental:

  If the global TLS initialisation could not be set up, ``tls_is_available()`` returns 0, otherwise 1.

  It is not very useful to call any other tls_* efun if this one returns 0, since there is no TLS-encryption available.

  Most likely the global initialisation failed due to a missing or unreadable key resp. certificate-file.

  :history 3.3.474 introduced:
  :history 3.2.11 backported:

  .. seealso:: :efun:`tls_init_connection`, :efun:`tls_deinit_connection`, :efun:`tls_query_connection_state`, :efun:`tls_query_connection_info`, :efun:`tls_check_certificate`, :efun:`tls_refresh_certs`