The following is a list of general response codes that may be sent by
   the NNTP server.  These are not specific to any one command, but may
   be returned as the result of a connection, a failure, or some unusual
   condition.

   In general, 1xx codes may be ignored or displayed as desired;  code
   200 or 201 is sent upon initial connection to the NNTP server
   depending upon posting permission; code 400 will be sent when the
   NNTP server discontinues service (by operator request, for example);
   and 5xx codes indicate that the command could not be performed for
   some unusual reason.

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      199 debug output

      200 server ready - posting allowed
      201 server ready - no posting allowed

      400 service discontinued

      500 command not recognized
      501 command syntax error
      502 access restriction or permission denied
      503 program fault - command not performed