Implementing SSH shell terminal in webapp using JSch

I am trying to implement a shell terminal in a webapp using websocket in spring. I am able to send a single command to the JSch "exec" channel and send the output back to the websocket.

The problem I am having is:

1. I am not able to retain the state of the shell like working directory, when I send a second command. How can I retain the previous state? I have tried using the same session but it does not work.

    public String sendCommand(String command) {
        StringBuilder outputBuffer = new StringBuilder();
   
        try {
            Channel channel = sesConnection.openChannel("exec");
            ((ChannelExec) channel).setCommand(command);
            InputStream commandOutput = channel.getInputStream();
            channel.connect();
            int readByte = commandOutput.read();
   
            while (readByte != 0xffffffff) {
                outputBuffer.append((char) readByte);
                readByte = commandOutput.read();
            }
   
            channel.disconnect();
        } catch (IOException ioX) {
            logWarning(ioX.getMessage());
            return null;
        } catch (JSchException jschX) {
            logWarning(jschX.getMessage());
            return null;
        }
   
        return outputBuffer.toString();
    }
   

   To send back to the websocket, in the controller I have :

   private SSHManager getSSHInstance() {
       String errorMessage = null;
   
       if (sshInstance == null) {
           sshInstance = new SSHManager(username, password, host, "", port);
           errorMessage = sshInstance.connect();
           System.out.println("Instance created");
           if (errorMessage != null) {
               throw new RuntimeException("Could not create an ssh connection");
           }
       }
       System.out.println("Returning created instance");
       return sshInstance;
   }
   
   @MessageMapping("/user")
   @SendTo("/topic/user")
   public UserResponse getResponse(String command) {
   
       SSHManager currInstance = getSSHInstance();
       String result = currInstance.sendCommand(command);
       return new UserResponse(result);
   }
   

2. I tried using the "shell" channel instead of "exec" which worked for getting the input and output through standard input and output stream but I could not get the real-time input and output from/back to the websocket and UI. I am not sure how to proceed from here. Any direction on where/what to look would be very helpful.

   Here is my code for the SSH terminal through standard input/output stream:

   import com.jcraft.jsch.*;
   
   public class Terminal{
       public static void main(String[] args){
   
           try{
               JSch jsch=new JSch();
   
               String host = "127.0.0.1";
               String user = "user";
               String password = "pass";
   
               Session session=jsch.getSession(user, host, 5679);
   
               session.setPassword(password);
               session.setConfig("StrictHostKeyChecking", "no");
               session.connect(10000);
   
               Channel channel=session.openChannel("shell");
   
               channel.setInputStream(System.in);
               channel.setOutputStream(System.out);
               channel.connect(3*1000);
           }
           catch(Exception e){
               System.out.println(e.getMessage());
           }
       }
   }
   

   To send the command from the UI, I have the following:

   function sendCommand() {
       if (stompClient != null) {
           stompClient.send("/app/user", {}, JSON.stringify({'command': $("#command").val()}));
       }
   }
   

If you want to implement an interactive shell, you have to use the "shell" channel, not the "exec" channel. The "exec" channel is intended for automating individual commands.

Some references:

• What is the difference between the 'shell' channel and the 'exec' channel in JSch
• JSch Shell.java example