Execute a command on a remote Shell using JSCH

[Marco Zanini]

Hi to all, I'm trying to remotely execute a command on a Linux shell using SSH. I'm using JSCH. But sometimes when I call the connect(int timeout) command it doesn't work, and sometimes seems that it blocks.

This is the code:

//executes a command on the remote shell
	public boolean executeCommand(String command) throws JSchException, IOException{
		if(!session.isConnected()){ 
			System.out.println("[SSHClient] Session not connected!"); 
			this.connectSession();
		} 
		ChannelExec channel = (ChannelExec) createChannel("exec");
		System.out.println("[SSHClient] Eseguo il comando: " + command);
		channel.setCommand(command + "\n");
		
		//connectInOut("linux", channel, System.in, System.out);
		// get I/O streams for remote scp
        OutputStream out=channel.getOutputStream();
	    //channel.setInputStream(null);
	    channel.setErrStream(System.err);
	    //channel.setOutputStream(System.out);
	    
	    //Do I have to connect to send commands?
	    //Allocate a pseudo-terminal 
	    //channel.setPty(true);
	    if(!session.isConnected()){ 
			System.out.println("[SSHClient] Sessione non connessa!"); 
			this.connectSession();
		} 
	    channel.connect(3000);
	    while(!channel.isConnected()){
			try {
				System.out.println("[SSHClient] Aspetto che la exec si connetta.");
				Thread.sleep(1000);
				channel.connect(1000);
			} catch (InterruptedException e) {e.printStackTrace(); System.out.println("[SSHClient] Thread interrotto.");}
		}
	    System.out.println("[SSHClient] Exec channel connected");
	    //channel.run();
	    
	    InputStream in = channel.getInputStream();
	    byte[] tmp=new byte[1024];
		while(true){
		    while(in.available()>0){
		      int i=in.read(tmp, 0, 1024);
		      if(i<0)break;
		      System.out.print(new String(tmp, 0, i));
		    }
		    if(channel.isClosed()){
		      System.out.println("exit-status: "+channel.getExitStatus());
		      break;
		    }
		    try{Thread.sleep(1000);}catch(Exception ee){ee.printStackTrace();}
	    }
		
	    channel.disconnect();
	    System.out.println("[SSHClient] Exec channel disconnected");
	    
		return true;
	}

How can I develop an error-proof connection?