Question

我已经建立了一个具有RETR和LIST命令的FTP客户端，但是遇到了问题。在我实现RETR命令后，我不断收到此错误：

1:220-FileZilla Server version 0.9.50 beta
1:220-written by Tim Kosse (tim.kosse@filezilla-project.org)
1:220 Please visit https://filezilla-project.org/
2331 Password required for geek
3230 Logged on
5227 Entering Passive Mode (127,0,0,1,217,137)
6200 Type set to A
7150 Opening data channel for directory listing of "/"
5227 Entering Passive Mode (127,0,0,1,217,139)
150 Opening data channel for directory listing of "/"
8501 Syntax error
Exception in thread "main" java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at ftp.ftp.connect(ftp.java:135)
at ftp.test.main(test.java:12)

此外，在我实现RETR命令后，客户端停止提供LIST命令;它不会告诉文件夹中有哪些文件。

public class ftp{
public synchronized void connect(String host, int port, String user,
        String pass) throws IOException {
    Socket socket = new Socket(host, port);

    BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
    BufferedWriter writer = new BufferedWriter(
            new OutputStreamWriter(socket.getOutputStream()));


    String response = reader.readLine();

    if (!response.startsWith("220-")) {
        throw new IOException(
                "FTP modtog et ukendt svar, da den blev forbundet til FTP server: "
                        + response);
    } else {System.out.println("1:"+response);
    response = reader.readLine();
    System.out.println("1:"+response);
    response = reader.readLine();
    System.out.println("1:"+response);


    }
    writer.write("user geek"+"\r\n");
    writer.flush();
    response= reader.readLine();
    System.out.println("2"+response);

    writer.write("PASS hello" +"\r\n");
    writer.flush();
    response= reader.readLine();
    System.out.println("3"+response);



    writer.write("pasv"+"\r\n");
    writer.flush();
    response= reader.readLine();
    System.out.println("5"+response );
    String [] r=response.trim().split(",");

    String reg=r[4];
    String add= r[5].replace(")", "");
    int m = Integer.parseInt(reg);
    int a = Integer.parseInt(add);

    int port1 = m*256+a;

    Socket datasocket = new Socket("127.0.0.1", port1);
    writer.write("type A\r\n");
    writer.flush();
    response= reader.readLine();
    System.out.println("6"+response);
    BufferedReader reader2 = new BufferedReader(new InputStreamReader(datasocket.getInputStream()));


    writer.write("LIST\r\n");
    writer.flush();
    response = reader.readLine();
    System.out.println("7" + response);

    List<String> files = new ArrayList<>();
    String text;
    while ((text = reader2.readLine()) != null) {
        String filename = parseFilename(text);
        files.add(filename);
    }
    reader2.close();
    datasocket.close();
    reader.readLine();

    for (String file : files) {
        int passivePort = getPort(reader, writer);
        writer.write("RETR\r\n");
        writer.flush();
        System.out.println(response);
        byte[] mybytearray = new byte[1024];

        try (Socket filesocket = new Socket("localhost", passivePort);
                InputStream is = filesocket.getInputStream();
                FileOutputStream fos = new FileOutputStream("c:/Users/Username/Desktop/FTP/" + file)) {
            int count;
            while ((count = is.read(mybytearray)) >= 0) {
                fos.write(mybytearray, 0, count);
            }
        }
    }

                writer.write("RETR\r\n");
            writer.flush();
            response= reader.readLine();
            System.out.println("8"+response);

                Socket filsocket = new Socket ("localhost", port1);
                InputStream is = null;
                FileOutputStream fos = null;

                byte[] mybytearray = new byte[1024];
            try {
                    is = filsocket.getInputStream();
                    fos = new FileOutputStream("myfile.txt");

                    int count;
                    while ((count = is.read(mybytearray)) >= 0) {
                        fos.write(mybytearray, 0, count);
                    }
                } finally {
                fos.close();
                    is.close();
                filsocket.close();
            }

}

private String parseFilename(String text) {

    return "abc.txt";
}

private int getPort(BufferedReader reader, BufferedWriter writer) throws IOException { //this is line 135
    String response;
    writer.write("PASV" + "\r\n");
    writer.flush();
    response = reader.readLine();
    System.out.println("5" + response);
    String[] r = response.trim().split(",");

    String reg = r[4];
    String add = r[5].replace(")", "");
    int m = Integer.parseInt(reg);
    int a = Integer.parseInt(add);

    return m * 256 + a;
}


}

提前致谢：）

Answer 1

RETR命令有一个必需参数，用于指定要下载的文件的名称。服务器如何知道，你想要下载哪个文件？

writer.write("RETR " + file + "\r\n");

请参阅RFC 959：

RETR <SP> <pathname> <CRLF>

无论如何，为什么要自己实现FTP协议？使用一些现有的实现，例如FTPClient from Apache Commons。

获取＆＃34; 501语法错误＆＃34;向FTP服务器发出RETR命令时

1 个答案: