How to tell if an SFTP upload was successful using JSch

Question

Unfortunately the getExitStatus() method always returns -1 so i can't use that to tell me whether or not a file upload worked. I tried to use the getInputStream() method of the Channel class but whenever i tried to read from the inputstream my code blocked forever as if the Channel instance was still open/connected (even though the isConnected and isClosed() were false and true respectively - suggesting that the Channel was indeed closed). The following code always blocks after i try to read a byte of data from the input stream:

public class Put {

public static void main(String[] args) throws IOException {

    Session session = null; 
    Channel channel = null; 
    ChannelSftp channelSftp = null; 
    InputStream in = null; 
    JSch jsch = new JSch();

    try {
        jsch.setKnownHosts("known_hosts");
        session = jsch.getSession("user", "host", 22);
        session.setPassword("password");

        session.connect();
        channel = session.openChannel("sftp");
        channel.setInputStream(null);
        stdout = channel.getInputStream();

        channel.connect();
        channelSftp = (ChannelSftp)channel;
        channelSftp.cd("/path/to/sftp");


        channelSftp.put("/path/to/localfile", "/path/to/remotefile");

    } catch (JSchException e) {
        System.out.println(e.getMessage());
        e.printStackTrace();
    } catch (SftpException e) {
        System.out.println(e.id);
        System.out.println(e.getMessage());
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {

        if(channelSftp != null && channelSftp.isConnected())channelSftp.exit();
        if(channel != null && channel.isConnected()) channel.disconnect();
        if(session != null && session.isConnected()) session.disconnect();
    }

    System.out.println("Channel is connected? " + channel.isConnected()); // returns false as i would expect
    System.out.println("Channel is closed? " + channel.isClosed()); // returns true as i would expect
    System.out.println(stdout.available()); // returns 0
    System.out.println(stdout.read()); // code blocks here

}

}

I suppose my questions are:

1. Why is my code blocking whenever i try to read from the input stream (even though the Channel is indeed closed)

2. What is the way to tell if a file upload worked or not. I guess if a SFTPException is thrown that's unsuccessful otherwise i can assume it was successful?

Answer 1

I guess if a SFTPException is thrown that's unsuccessful otherwise i can assume it was successful?

That is correct. The various ChannelSftp.put() functions will throw an exception if they fail for any reason. If you want to double-check, you could call ChannelSftp.stat() or ...lstat() on the remote filename afterwards to check it. But be aware that another process could hypothetically delete or move the remote file before you got a chance to check it.

You don't normally need to access the input or output streams of a ChannelSftp. getExitStatus() would tell you the exit status of the SFTP session as a whole, rather than the result of a particular operation.

JCraft has an example program illustrating how to do SFTP that you might find useful.