anchor.diff:  using a Virtual Layer 2 packet facility.
   
   CAUTION: This transport is very experimental.  To utilize it at
  -         present, the library must be built with support, and the
  -         ZeroTierOne `dev` branch must be included; this will require
  -         linking against a suitable `libzerotiercore` static library.         
  +present, the library must be built with support, and the
  +ZeroTierOne `dev` branch must be included; this will require
  +linking against a suitable `libzerotiercore` static library.         
   
   NOTE: The `libzerotiercore` library at present is covered under different
  -      license terms than the rest of _nng_.  Please be careful to review
  -      and adhere to the licensing terms.
  +license terms than the rest of _nng_.  Please be careful to review
  +and adhere to the licensing terms.
   
   While ZeroTier makes use of the host's IP stack (and UDP in particular),
   this transport does not use or require an IP stack on the virtual
  
positive.code:   is to use an ephemeral node.
  + 
  NOTE: If this option is set to different values on different sockets,
        dialers, or listeners, then separate nodes will be created.  It
        is perfectly valid for an application to have multiple node identities
        in this fashion.
  
  *NNG_OPT_ZT_NWID*::
  
  
negative.code: Listening nodes may also elide their own node number, as well as the
  delimiter seperating the node number.
  
  Socket Address
  ~~~~~~~~~~~~~~
  
  When using an `nng_sockaddr` structure, the actual structure is of type
  `struct nng_sockaddr_zt`.  This type has the following definition:
  
  [source,c]
  --------
  #define NNG_AF_ZT 5
  
  struct nng_sockaddr_zt {
      uint16_t sa_family;  // must be NNG_AF_ZT
      uint64_t sa_nwid;    // 40-bit network ID
      uint64_t sa_nodeid;  // 64-bit node ID
      uint32_t sa_port;    // 24-bit application port
  }
  --------
  
  The `sa_family` member will have the value `NNG_AF_ZT` (5).  The remaining
  members are, unlike TCP socket address, in native byte order.  Only the
  lower 24-bits of the `sa_port` may be used.  Likewise only the lower 40-bits
  of the `sa_nwid` may be used.
  
  Node Presence
  ~~~~~~~~~~~~~
  