declare
proc {NewPortObjects ?AddPortObject ?Call}
   Sin P={NewPort Sin}

   proc {MsgLoop S1 Procs}
      case S1
      of add(I Proc Sync)|S2 then Procs2 in
         Procs2={AdjoinAt Procs I Proc}
         Sync=unit
         {MsgLoop S2 Procs2}
      [] msg(I M)|S2 then
         try {Procs.I M} catch _ then skip end
         {MsgLoop S2 Procs}
      [] nil then skip end
   end
in
   thread {MsgLoop Sin procs} end

   proc {AddPortObject I Proc}
   Sync in
      {Send P add(I Proc Sync)}
      {Wait Sync}
   end

   proc {Call I M}
      {Send P msg(I M)}
   end
end