使用java.net在Java中创建FTP客户端-拒绝连接：connect

Question

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;

public class FTPClient {
protected Socket sk;
protected BufferedReader in;
protected BufferedWriter out;

public static void main (String [] args){
    FTPClient fc1 = new FTPClient("sitename.org",21);
    fc1.Login("user", "password!");
}

FTPClient(String server, int port){
    try{
        this.sk = new Socket(server,port);
        this.in = new BufferedReader(new InputStreamReader(sk.getInputStream()));
        this.out = new BufferedWriter(new OutputStreamWriter(sk.getOutputStream()));

        String response = in.readLine();
        System.out.println(response);
    }
    catch(Exception e){
        System.out.println(e);
    }

}

public boolean Login(String user, String pass){
    boolean success = false;
    try{
        sendOut("USER " + user);
        sendOut("PASS " + pass);
        success = true;
        System.out.println("Waiting for response");
        String response = in.readLine();
        System.out.println(response);

    }
    catch(Exception e){
        System.out.println("Login Failure");
        success = false;
    }

    return(success);
}

public void sendOut(String command) throws Exception{
    if (sk == null){
        throw new Exception("Client is not connected!");
    }

    try{
        out.write(command + "\r\n");
        out.flush();
    }
    catch(Exception e){
        System.out.println(e);
    }
}

}

Hello, I wrote this code as a client to try to connect and login to a server with an FTP connection. However, I keep getting this error message, java.net.ConnectException: Connection refused: connect Can someone please help me?

Answer 1

You try to connect to a SSH server, hence you get the unexpected reply. The defualt FTP port is 21.

Answer 2

Ok... My School's server doesn't have FTP set up and opened on port 21. So, I started FTP on my server on port 21 and it properly connect now. Thanks for helping me trouble shoot guys.

Lessons learned: FTP is normally on port 21. However, if there are connection problems, one should check if the server is even listening on port 21 by logging on and using the "sudo netstat netstat -lntu" command. If FTP is not even on, one can install it by running "sudo apt-get install vsftpd".

Thanks everyone for helping me troubleshoot to the answer.