java - FTP 在 5 分钟不活动后不工作

Question

我有一个进行模拟的应用程序。在每次模拟开始时，都会创建 FTP 连接，然后完成一些上传/下载文件操作。然后开始仿真。仿真结束后，再次进行一些上传文件操作，备份仿真相关文件夹

如果模拟时间超过 5 分钟，我们会遇到问题。与此同时，FTP 连接空闲。我会遇到以下异常。

java.net.SocketException: Software caused connection abort: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:202)
at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:272)
at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:276)
at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:122)
at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:212)
at java.io.BufferedWriter.flush(BufferedWriter.java:236)
at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:477)
at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:537)
at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:586)
at org.apache.commons.net.ftp.FTP.quit(FTP.java:794)
at org.apache.commons.net.ftp.FTPClient.logout(FTPClient.java:788)


Caused by: java.net.SocketException: Software caused connection abort: recv failed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
at java.io.InputStreamReader.read(InputStreamReader.java:167)
at java.io.BufferedReader.fill(BufferedReader.java:136)
at java.io.BufferedReader.readLine(BufferedReader.java:299)
at java.io.BufferedReader.readLine(BufferedReader.java:362)
at org.apache.commons.net.ftp.FTP.__getReply(FTP.java:295)
at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:495)
at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:537)
at org.apache.commons.net.ftp.FTP.mkd(FTP.java:1363)
at org.apache.commons.net.ftp.FTPClient.makeDirectory(FTPClient.java:1971)

我在模拟完成后尝试了以下操作，我尝试重新初始化 FTP，但没有成功。我看到 FTP 端的连接是 Activity 的

1)FTPClient.isConnected()方法返回true

2)当我调用 FTPClient.connect() 时，它抛出异常 FTP is already initialized

3)我尝试在 FTP 的连接方法中设置超时。

public boolean connect() throws IllegalStateException, FileTransferException {
    /*
     * Precondition checks
     */
    final FTPClient clientBefore = this.getClient();
    if (clientBefore != null && clientBefore.isConnected()) {
        throw new IllegalStateException("FTP Client is already initialized");
    }
    // Create the client
    final FTPClient client = new FTPClient();
    client.setConnectTimeout(600000);
    client.setDefaultTimeout(600000);
    // FTPClientConfig conf = new FTPClientConfig(FTPClientConfig.SYST_NT);
    // client.configure(conf);
    log.trace("Connecting to FTP Server at " + config.getCanonicalForm());
    try {
        client.connect(config.getHost(), config.getPort());
        client.setSoTimeout(600000);
    } catch (final IOException ioe) {
        throw new FileTransferException("Error in connecting to " + config.getCanonicalForm(),
                ioe);
    }
    log.trace("Connected to FTP Server at: " + config.getCanonicalForm());
    this.setClient(client);
    // Check that the last operation succeeded
    this.checkLastOperation();
    boolean result;
    try {
        // Login
        if (client.login(config.getUserName(), config.getPassword())) {
            result = true;
            // If there's a pwd defined, cd into it.
            final String pwd = this.getPresentWorkingDirectory();
            if (pwd != null) {
                this.cd(pwd);
            }
        } else {
            result = false;
        }
    } catch (final Exception e) {
        throw new FileTransferException("Could not log in", e);
    }
    return result;
}

现在，我陷入了僵局，我不知道是什么问题

Answer 1

如果您真的必须保持连接有效，请对服务器运行 NOOP 命令，以便控制连接保持有效。

要么手动执行:

client.sendNoOp();

或者设置客户端以固定的间隔速率执行:

client.setControlKeepAliveTimeout(300); // set timeout to 5 minutes

但如果你能避免浪费资源，logout和 disconect在初始下载阶段之后，进行本地处理和 connect/login之后再次上传。