Endpoint implementations of various SSH interactions.
| Class | AuthenticationFailed | An SSH session could not be established because authentication was not successful. | 
| Class | SSHCommandAddress | An SSHCommandAddressinstance represents the address of an SSH server, a username which was used
to authenticate with that server, and a command which was run there. | 
| Class | SSHCommandClientEndpoint | SSHCommandClientEndpointexposes the command-executing functionality of SSH servers. | 
| Interface | _ISSHConnectionCreator | An _ISSHConnectionCreatorknows how to create SSH connections somehow. | 
| Class | _CommandChannel | A _CommandChannelexecutes a command in a session channel and connects its input and output 
to anIProtocolprovider. | 
| Class | _ConnectionReady | _ConnectionReadyis anSSHConnection(an SSH service) which only propagates the serviceStarted event to aDeferredto
be handled elsewhere. | 
| Class | _UserAuth | _UserAuthimplements the client part of SSH user authentication in the convenient way
a user might expect if they are familiar with the interactive ssh 
command line client. | 
| Class | _CommandTransport | _CommandTransportis an SSH client transport which includes a host key verification 
step before it will proceed to secure the connection. | 
| Class | _ReadFile | A weakly file-like object which can be used with KnownHostsFileto respond in the negative to all prompts for decisions. | 
| Class | _NewConnectionHelper | _NewConnectionHelperimplements_ISSHConnectionCreatorby establishing a brand new SSH connection, securing it, and 
authenticating. | 
| Class | _ExistingConnectionHelper | _ExistingConnectionHelperimplements_ISSHConnectionCreatorby handing out an existing SSH connection which is supplied to its 
initializer. |