如何测试Java SSH客户端JSch？本地测试遇连接拒绝问题求助

Hey there! Let's work through this JSch connection issue together—since you're testing locally, this should be fixable with a few straightforward checks and tweaks.

1. First, Make Sure Your Local SSH Server is Running #

This is the most common cause of the "connection refused" error when testing locally:

• Windows: You need to enable the OpenSSH Server feature first. Head to Settings > Apps > Optional features > Add a feature, search for "OpenSSH Server", install it, then open services.msc, find "OpenSSH SSH Server", set its startup type to Automatic, and start the service.
• macOS/Linux: SSH servers are usually pre-installed, but double-check if it's running. Use sudo systemctl status sshd (Linux) or sudo launchctl list | grep sshd (macOS) to verify. If it's stopped, start it with sudo systemctl start sshd (Linux) or sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist (macOS).

2. Fix Your Connection Details in the Code #

Your current code uses placeholders like "username" and "host ip"—swap these for local-specific values:

• user: Use your actual local machine username (run whoami in terminal to get this)
• host: Replace with "localhost" or "127.0.0.1" (both point directly to your own machine)
• port: 22 is the default SSH port, but double-check your SSH server config (usually /etc/ssh/sshd_config on Linux/macOS, or Windows SSH settings) to confirm it's not using a different port.

3. Verify Your Private Key Setup #

• Path correctness: On Linux/macOS, the private key path should be ~/.ssh/id_rsa (note the tilde, which points to your home folder—using just .ssh/id_rsa will look in your Java program's current working directory, not your home). On Windows, it's typically C:\Users\YourUsername\.ssh\id_rsa.
• Permissions: SSH rejects keys with overly open permissions. On Linux/macOS, run chmod 600 ~/.ssh/id_rsa to lock down access. On Windows, right-click the file > Properties > Security > Advanced, and ensure only your user account has access to it.

4. Test the SSH Connection Manually First #

Before debugging code, test a local SSH connection via terminal to rule out server issues:

ssh your-local-username@localhost -p 22

If this works, the problem is in your code; if not, fix the SSH server or config first.

5. Revised Local Test Code #

Here's a tweaked version of your code with local-friendly values and basic error handling to help you debug:

import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;

public class LocalJSchTest {
    public static void main(String[] arg) {
        try {
            JSch jsch = new JSch();
            // Auto-get your local username
            String user = System.getProperty("user.name");
            String host = "localhost";
            int port = 22;
            // Auto-point to your home directory's private key
            String privateKey = System.getProperty("user.home") + "/.ssh/id_rsa";

            jsch.addIdentity(privateKey);
            System.out.println("Connecting to " + host + ":" + port + " as " + user);

            Session session = jsch.getSession(user, host, port);
            // Disable strict host checking for local testing (don't do this in production!)
            session.setConfig("StrictHostKeyChecking", "no");
            session.connect();

            System.out.println("Successfully connected!");
            // Add your SSH operations here (e.g., run commands, transfer files)

            session.disconnect();
        } catch (Exception e) {
            System.out.println("Connection failed: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

Quick Final Check #

If you still get the error, make sure your local firewall isn't blocking port 22—temporarily disable it for testing to confirm. And remember, for production code, never disable StrictHostKeyChecking; instead, add your local host key to the known_hosts file first.

内容的提问来源于stack exchange，提问作者Aleksandar Grujic