SilcClientEntry silc_client_get_client_by_id(SilcClient client,
                                                 SilcClientConnection conn,
                                                 SilcClientID *client_id);

    Find client entry by the client's ID.  Returns the entry or NULL
    if the entry was not found.  This checks the local cache and does
    not resolve anything from server.

    The returned SilcClientEntry has been referenced by the library and
    the caller must call silc_client_unref_client after the entry is not
    needed anymore.