How to connect to multiple parallel SFTP using JSCH?

I'm using JSCH to connect to SFTP. What I'm trying to do is, I have some SFTP url, hostname and password stored in my database. Using query, I'll select ,say 5, url, hostname and password form my database and establish SFTP connection to transfer some file. I'm able to connect to SFTP one at time using a for or while loop. But I want to connect to SFTP parallelly. I tried the ExecutorService to create a thread pool to establish parallel connection but it is throwing an error.

ExecutorService executor = Executors.newFixedThreadPool(n);
for(int i = 0; i<n; i++){
Runnable task = new SFTPTask(outbound);
executor.submit(task);
}

executor.shutdown();
executor.awaitTermination(interval, TimeUnit.SECONDS);



class SFTPTask implements Runnable {

		SchedulerOutbound outbound;

		public SFTPTask(SchedulerOutbound outbound) {
			this.outbound = outbound;
		}

		@Override
		public void run() {

			List<SFTPUser> list = service.getList(outbound.getProvider());

			filename = outbound.getDataX12().split("IEA")[1].split("\\*")[2]
					.split("~")[0]
					+ "." + fileExt;

			try {
				BufferedOutputStream out = new BufferedOutputStream(
						new FileOutputStream(sourceFolder + filename));
				byte[] dataInByte = outbound.getDataX12().getBytes();
				out.write(dataInByte);

				out.flush();
				out.close();
			} catch (FileNotFoundException e) {

				e.printStackTrace();

			} catch (IOException e) {

				e.printStackTrace();

			}

			loginId = list.get(0).getLoginFk();
			url = list.get(0).getSftpUrl();
			login = list.get(0).getSftpLogin();
			password = list.get(0).getSftpPasswd();
			host = url.split("//")[1].split(":")[0];
			port = Integer.parseInt(url.split(":")[2]);
			System.out.println(loginId + url + login + password);
			try {

				JSch jsch = new JSch();
				session = jsch.getSession(login, host, port);
				session.setPassword(password);
				Properties config = new java.util.Properties();
				config.put("StrictHostKeyChecking", "no");
				session.connect();
				channel = session.openChannel("sftp");
				channel.connect();
				ChannelSftp channelSftp = (ChannelSftp) channel;

				channelSftp.cd(destFolder);

				File f = new File(sourceFolder + filename);

				channelSftp.put(new FileInputStream(f), f.getName());

				service.updateDataProcessed(outbound);
				 f.delete();
				channelSftp.exit();

			} catch (Exception e) {
				service.setAuthStatus(loginId, "failed");
				e.printStackTrace();

			} finally {
				if (channel != null) {
					channel.disconnect();
					session.disconnect();
					service.setAuthStatus(loginId, "success");
				}
			}
		}
	}
      

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I'm getting the following errors:

com.jcraft.jsch.JSchException: session is down

com.jcraft.jsch.JSchException: connection is closed by foreign host
spectrumsofttechAsked:
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mccarlConnect With a Mentor IT Business Systems Analyst / Software DeveloperCommented:
What you posted above must be some *edited* form of your code, and the bits that you have edited out and probably crucial to solving this problem!!

In particular I would need to see how and where you have declared the "session" and "channel" variables. My guess is that they are declared in a scope that means there is only one instance of these variable shared among ALL threads. And so, on line 57 for example, you will have all X number of threads trying to set the *same* session variable to different values. The same for the channel variable.
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Dave BaldwinFixer of ProblemsCommented:
Since SFTP runs thru SSH on port 22, I don't see how you can make multiple connections on the same port at the same time.  Unless there is a way to use multiple source ports on your machine.
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spectrumsofttechAuthor Commented:
Yes, host and port may be same but the sftp login and password will be different. Shouldn't it be possible to connect to multiple sftp in parallel, if you have different login and password credentials even though host and port are the same?
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Dave BaldwinFixer of ProblemsCommented:
I suspect that there is only one thread and only one instance of all the variables.  To make it even possible, you would have to have a thread for each instance (I believe) and multiple source ports.  I know that in TCPView when you see Firefox making multiple connections, all the source ports are different.  I may be wrong but I don't think you can have multiple instances or programs using the same port at the same time.
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spectrumsofttechAuthor Commented:
Your guess about session and channel was correct. That hint was enough to solve my problem. Thank you for the help.
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mccarlIT Business Systems Analyst / Software DeveloperCommented:
You're welcome, glad I could help! :)
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