JSch Client Exec Channel Example with flushing data — run command passwd
JSch is a pure Java library that implemens SSH2. However, it is poorly documented and finding a good example is difficult. I’ll demonstrate how we can use JSch in a more efficient manner, I chose the “passwd” command because it prompts you for a new password when you type it into the shell terminal. Let’s begin by implementing the “host” class:
Continue by implementing auth method classes:
Carry on with the implementation of the Authentication class, which has a user name and a corresponding authentication method:
Let’s implement an enumeration to keep track of different ssh channel types:
Carry on with the implementation of the Client Session Operator which takes host name, authentication and preferably the connection port as parameters to init and start session as well as create appropriate ssh channel. (Only the Exec channel will be implemented)
Lets create the most important class that will allow us to operate more efficiently:
ExecInteract is a class that takes an exec channel and a command string as parameters and runs it on that channel.
- executeTimeout is the amount of time to run commands on channel and get a response. Extended classes have the ability to adjust this as needed.- If the execute timed out and the channel is yet not closed, the channelDisconnectTimer is responsible for disconnecting the channel.- flushing functions will be explained later.
Let’s make StandardExecInteract class that takes a command and executes it on channel exec, then waits for a response.
At this stage, see an example of command running using the Standard Interact class:
This is the ide output:
When you perform the passwd command, the exec channel console prompts you for a new password and waits for interact; if no interact occurs after 2000 milliseconds, the channel is immediately closed.
Let’s make a class that runs the passwd command and flushes the new password (twice) (systematically) when the exec channel prompts for it.
The ide result is: