SSH: Work with subsystems in the SSH server
Subsystems is an easy method to extend SSH protocol with support for third-party application layer protocols. Essentially, an SSH subsystem can be viewed as a named tunnel type which can be used to forward data of specific protocol. The most well-known subsystem is SFTP.
Subsystems work in exactly the same way as SSH channels of other type. For each activated subsystem channel you receive a TElSSHTunnelConnection object which you then use for sending and receiving data over the channel.
An important difference, however, is that you must specify the names of all subsystems that you want to use explicitly via the AllowedSubsystems property of your TElSSHServer object. This was done for security reasons so that only legitimate subsystems could have been created by the connecting users.
The procedure is therefore as following: