"Connection is not open" FTP Android

Question

每次尝试连接时，我都会遇到异常 "Connection is not open"。当我尝试通过 FileZilla 或浏览器访问时，服务器运行良好。

我正在使用 apache-common-net 库。

private Boolean downloadAndSaveFile(String server, int portNumber,
                                    String user, String password, String filename, File localFile)
        throws IOException {
    FTPClient ftp = null;

    try {
        ftp = new FTPClient();
        ftp.connect(server, portNumber);

        ftp.login(user, password);

        ftp.setFileType(FTP.BINARY_FILE_TYPE);

        ftp.enterLocalPassiveMode();

        OutputStream outputStream = null;
        boolean success = false;
        try {
            outputStream = new BufferedOutputStream(new FileOutputStream(
                    localFile));
            success = ftp.retrieveFile(filename, outputStream);
        } finally {
            if (outputStream != null) {
                outputStream.close();
            }
        }

        return success;
    } finally {
        if (ftp != null) {
            ftp.logout();
            ftp.disconnect();
        }
    }
}

实施：

 private Boolean buttonDo(String atividade, int groupPosition, int childPosition)  {
    try {
        downloadAndSaveFile(servidor, porta, user, password, filename, filelocation);

    }catch (IOException e) {
        Toast.makeText(_context,e.getMessage(),Toast.LENGTH_SHORT).show();

    }
    return false;
}

日志：

java.io.IOException: Connection is not open
 at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:514)
 at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:648)
 at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:622)
 at org.apache.commons.net.ftp.FTP.quit(FTP.java:904)
 at org.apache.commons.net.ftp.FTPClient.logout(FTPClient.java:1148)
 at com.joaobernardos.joaobernardo.gave.ExpandableListAdapter.downloadAndSaveFile(ExpandableListAdapter.java:124)
 at com.joaobernardos.joaobernardo.gave.ExpandableListAdapter.buttonDo(ExpandableListAdapter.java:198)
 at com.joaobernardos.joaobernardo.gave.ExpandableListAdapter.access0(ExpandableListAdapter.java:34)
 at com.joaobernardos.joaobernardo.gave.ExpandableListAdapter.onClick(ExpandableListAdapter.java:241)
 at android.view.View.performClick(View.java:4756)
 at android.view.View$PerformClick.run(View.java:19761)
 at android.os.Handler.handleCallback(Handler.java:739)
 at android.os.Handler.dispatchMessage(Handler.java:95)
 at android.os.Looper.loop(Looper.java:135)
 at android.app.ActivityThread.main(ActivityThread.java:5253)
 at java.lang.reflect.Method.invoke(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:372)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

所以，我去探索 FTP.class 并发现了导致异常的原因：

 public int sendCommand(String command, String args) throws IOException {
    if(this._controlOutput_ == null) {
        throw new IOException("Connection is not open");
    } else {
        String message = this.__buildMessage(command, args);
        this.__send(message);
        this.fireCommandSent(command, message);
        this.__getReply();
        return this._replyCode;
    }
}

我没有使用工作线程。我是不是该？我该如何实施？

Answer 1

确保发送正确的端口号。请与服务器管理员核实。端口不一定是 22，有时可能会为 FTP

设置不同的端口号

Answer 2

当您“尝试连接” 时，您没有遇到异常。当您注销时，您会得到它。

我猜想，实际发生的是，try 块中的代码抛出异常，而没有实际连接。然后您尝试在 finally 块中注销，抛出什么，因为您从未登录过。

删除 ftp.logout() 和 ftp.disconnect() 以避免吞下主要异常，看看什么时候是您的实际问题。

当您在 GUI 线程上执行网络操作时，很可能这是实际问题所在。主要例外可以是 NetworkOnMainThreadExeption.
参见 How to fix 'android.os.NetworkOnMainThreadException'?

Answer 3

先注销 ftp.logout()，然后 ftp.disconnect()，对我有用:)

public boolean disconnectFromFtpServer() {
    try {
        ftpClient.logout();
        ftpClient.disconnect();
        return true;
    } catch (IOException ioException) {
        ioException.printStackTrace();
    }
    return false;
}

"Connection is not open" FTP Android

"Connection is not open" FTP Android

java

ftp

android

apache-commons-net