anchor.diff:      S = ok(gen_udp:open(0, [{ifaddr,SAddr},{active,false}])),
       C = ok(gen_udp:open(0, [local,{active,false}])),
       SAddr = ok(inet:sockname(S)),
  -    {local,<<>>} = ok(inet:sockname(C)),
  -    local_handshake(S, SAddr, C, {unspec,<<>>}),
  +    local_handshake(S, SAddr, C, undefined),
       ok = gen_udp:close(S),
       ok = gen_udp:close(C),
       %%
  
positive.code:     S = ok(gen_udp:open(0, [{ifaddr,SAddr},{active,false}])),
      C0 = ok(gen_udp:open(0, [local,{active,false}])),
      SAddr = ok(inet:sockname(S)),
      {local,<<>>} = ok(inet:sockname(C0)),
      Fd = ok(prim_inet:getfd(C0)),
      C = ok(gen_udp:open(0, [{fd,Fd},local,{active,false}])),
      {local,<<>>} = ok(inet:sockname(C)),
      local_handshake(S, SAddr, C, {unspec,<<>>}),
      ok = gen_udp:close(S),
      ok = gen_udp:close(C),
      ok = gen_udp:close(C0),
  
negative.code:     SData = "9876543210",
      CData = "0123456789",
      ok = gen_udp:send(C, SAddr, 0, CData),
      case ok(gen_tcp:recv(S, 112)) of
  	{{unspec,<<>>}, 0, CData} when CAddr =:= undefined ->
  	    ok;
  	{{local,<<>>}, 0, CData} when CAddr =:= undefined ->
  	    ok;
  	{CAddr, 0, CData} when CAddr =/= undefined ->
  	    ok = gen_udp:send(S, CAddr, 0, SData),
  	    {SAddr, 0, SData} = ok(gen_tcp:recv(C, 112)),
  	    ok
  
      end.
  
  %%
  %% Utils
  