anchor.diff:                FileOpts, DoItFun,
                 EpochID, Wedged_p, CurrentEpochId);
           {error, enoent} when OptsHasRead ->
  -            ok = gen_tcp:send(Sock, <<"ERROR NO-SUCH-FILE\n">>);
  +            ok = NoSuchFileFun(Sock);
           _Else ->
  -            ok = gen_tcp:send(Sock, <<"ERROR BAD-IO\n">>)
  -    end.
  -
  +            ok = BadIoFun(Sock)
  +    end.
   
   do_net_server_write(Sock, OffsetHex, LenHex, FileBin, DataDir,
                       EpochID, Wedged_p, CurrentEpochId) ->
  
positive.code: do_net_server_readwrite_common2(Sock, OffsetHex, LenHex, FileBin, DataDir,
                                  FileOpts, DoItFun,
                                  EpochID, Wedged_p, CurrentEpochId) ->
      <<Offset:64/big>> = machi_util:hexstr_to_bin(OffsetHex),
      <<Len:32/big>> = machi_util:hexstr_to_bin(LenHex),
      {_, Path} = machi_util:make_data_filename(DataDir, FileBin),
  
negative.code:           epoch_id        :: 'undefined' | pv1_epoch(),
            dbg_props = []  :: list(), % proplist
            props = []      :: list()  % proplist
           }).
  
  -record(http_goop, {
            len                                   % content-length
           }).
  
  start_link([{FluName, TcpPort, DataDir}|Rest])
  