# 15.3 Built-in Module `ctb`

This module provides a partial interface to the Macintosh Communications Toolbox. Currently, only Connection Manager tools are supported. It may not be available in all Mac Python versions.

`error`
  The exception raised on errors.

`cmData`
  ,cmCntl ,cmAttn Flags for the channel argument of the Read and Write methods.

`cmFlagsEOM`
  End-of-message flag for Read and Write.

`choose*`
  Values returned by Choose.

`cmStatus*`
  Bits in the status as returned by Status.

`available` ()
  Return 1 if the communication toolbox is available, zero otherwise.

`CMNew` (name, sizes)
  Create a connection object using the connection tool named name. sizes is a 6-tuple given buffer sizes for data in, data out, control in, control out, attention in and attention out. Alternatively, passing `None` will result in default buffer sizes.

- 15.3.1 connection object