FileZilla SFTP Disconnected from Server: A Comparison of Java Code and FileZilla Configuration

When attempting to connect to an SFTP server using a Java code, it is not uncommon to encounter errors that are not present when using FileZilla or other GUI-based clients. One such error is the 'connection is closed by foreign host' message, which can be frustrating and challenging to resolve. In this article, we will examine the possible causes of this error and explore ways to troubleshoot and resolve it.

The Java code used in this example is as follows:

```

Session session = jsch.getSession('test', 'localhost', 21)

JSch jsch = new JSch()

```

This code attempts to establish a connection to an SFTP server on localhost, using port 21 and the username 'test'. However, when run, it produces the error message 'connection is closed by foreign host'.

The error message suggests that the remote host (in this case, the SFTP server) has terminated the connection. This can occur due to a number of reasons, including:

1. Authentication issues: The username or password used in the Java code may be incorrect or not recognized by the SFTP server.

2. Connection timeouts: The Java code may be timing out before establishing a connection to the SFTP server.

3. Firewall or network configuration issues: Firewalls or network configurations may be blocking the connection between the Java code and the SFTP server.

To troubleshoot this issue, it is essential to examine the error message in more detail and consider the following potential causes:

1. Check the username and password: Verify that the username and password used in the Java code are correct and match those configured on the SFTP server.

2. Inspect the connection timeout settings: Check the connection timeout settings in the Java code and ensure they are set to a reasonable value, such as 30 seconds or more.

3. Verify firewall and network configurations: Check that firewalls and network configurations do not block the connection between the Java code and the SFTP server.

In contrast, FileZilla is able to establish a successful connection to the same SFTP server without any errors. This suggests that the issue lies with the Java code or its configuration rather than the SFTP server itself.

To resolve this issue, it may be necessary to modify the Java code to address the potential causes outlined above. For example, adding additional error handling or modifying the timeout settings can help prevent the connection from being closed prematurely.

In conclusion, when attempting to connect to an SFTP server using a Java code and encountering errors like 'connection is closed by foreign host', it is essential to examine the error message carefully and consider potential causes such as authentication issues, connection timeouts, or firewall and network configuration issues. By troubleshooting these potential causes and modifying the Java code accordingly, it may be possible to establish a successful connection to the SFTP server.

Filezilla sftp disconnected from server