TransportOSError in chat example

[Swader]

Repro:

• nim c -r --threads:on examples/chat.nim
• ./example/chat

Then, open another instance on the same machine. Result:

λ examples\chat.exe
chat.nim(130)            chat
asyncmacro2.nim(334)     main
asyncmacro2.nim(36)      main_continue
chat.nim(108)            mainIter
stream.nim(1299)         start
stream.nim(935)          resumeAccept
stream.nim(804)          acceptPipeLoop
common.nim(476)          raiseTransportOsError
[[reraised from:
chat.nim(130)            chat
asyncloop.nim(915)       waitFor
asyncfutures2.nim(432)   read
]]
Error: unhandled exception: (5) Access is denied.

Async traceback:
  chat.nim(130)        chat
  asyncmacro2.nim(334) main
  asyncmacro2.nim(36)  main_continue
  chat.nim(108)        mainIter
  stream.nim(1299)     start
  stream.nim(935)      resumeAccept
  stream.nim(804)      acceptPipeLoop
  common.nim(476)      raiseTransportOsError
Exception message: (5) Access is denied.

Exception type: [TransportOsError]