Question

我知道这是我已经深入研究的一些异步难题，但是我试图在任何npm的各种FTP软件包的.list方法的回调中下载多个文件。

这样的事情（注意：这里的JSFTP只是node-ftp的一个包装器，我遇到了同样的问题）：

  ftp = new JSFTP(conf.FTPConfig)
  ftp.ls(conf.remoteFolder, (err, fileList) => {
    if (err) return console.error(err)

    for (let i=0; i<fileList.length; i++){
      file = fileList[i]
      ftp.get(file.name, `./Downloaded/${file.name}`, err => {
        if (err) return console.error(err)
        console.log(`${file.name} copied.`)
      })
    }
  })

如果我不使用循环只下载一个文件，一切正常。但是通过循环，我不断收到以下错误，并且我没有得到任何文件（除了一个或两个空文件占位符）：

（简而言之）：Error: 503 Bad sequence of commands，以及下方：'Probably trying a PASV operation while one is in progress

看起来它启动了我在循环中的所有.get调用（显然没有等待它们中的任何一个完成，这很好），但是然后无法以这种方式实际执行所有.get调用？它们不应该只是异步并行运行吗？

{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:257:11)
    at Ftp.parseResponse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:174:8)
    at Stream.<anonymous> (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:\Git\SenecaFTP\FTPMonitor\node_modules\duplexer\index.js:70:25)
    at emitOne (events.js:96:13)
    at ResponseParser.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:172:18)
    at ResponseParser.Readable.push (_stream_readable.js:130:10) code: 503 }
{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:257:11)
    at Ftp.parseResponse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:174:8)
    at Stream.<anonymous> (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:\Git\SenecaFTP\FTPMonitor\node_modules\duplexer\index.js:70:25)
    at emitOne (events.js:96:13)
    at ResponseParser.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:172:18)
    at ResponseParser.Readable.push (_stream_readable.js:130:10) code: 503 }
{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:257:11)
    at Ftp.parseResponse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:174:8)
    at Stream.<anonymous> (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:\Git\SenecaFTP\FTPMonitor\node_modules\duplexer\index.js:70:25)
    at emitOne (events.js:96:13)
    at ResponseParser.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:172:18)
    at ResponseParser.Readable.push (_stream_readable.js:130:10) code: 503 }
{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:257:11)
    at Ftp.parseResponse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:174:8)
    at Stream.<anonymous> (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:\Git\SenecaFTP\FTPMonitor\node_modules\duplexer\index.js:70:25)
    at emitOne (events.js:96:13)
    at ResponseParser.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:172:18)
    at ResponseParser.Readable.push (_stream_readable.js:130:10) code: 503 }
{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:257:11)
    at Ftp.parseResponse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:174:8)
    at Stream.<anonymous> (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:\Git\SenecaFTP\FTPMonitor\node_modules\duplexer\index.js:70:25)
    at emitOne (events.js:96:13)
    at ResponseParser.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:172:18)
    at ResponseParser.Readable.push (_stream_readable.js:130:10) code: 503 }
{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:257:11)
    at Ftp.parseResponse (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:174:8)
    at Stream.<anonymous> (C:\Git\SenecaFTP\FTPMonitor\node_modules\jsftp\lib\jsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:\Git\SenecaFTP\FTPMonitor\node_modules\duplexer\index.js:70:25)
    at emitOne (events.js:96:13)
    at ResponseParser.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:172:18)
    at ResponseParser.Readable.push (_stream_readable.js:130:10) code: 503 }
{ Error: connect ECONNREFUSED 192.168.100.161:61229
    at Object.exports._errnoException (util.js:1007:11)
    at exports._exceptionWithHostPort (util.js:1030:20)
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1080:14)
  code: 'ECONNREFUSED',
  errno: 'ECONNREFUSED',
  syscall: 'connect',
  address: '192.168.100.161',
  port: 61229,
  msg: 'Probably trying a PASV operation while one is in progress' }

Answer 1

在查看jsftp的源代码之后，它似乎创建了一个连接并只使用了一个套接字：https://github.com/sergi/jsftp/blob/master/lib/jsftp.js#L120

这意味着它不会为每个命令创建新连接，而是使用单个连接来发送命令。基本上，您可以通过为要上载的每个文件创建新的SFTP实例来避免这种情况。

基本上将代码重写为：

＆＃13;

ftp = new JSFTP(conf.FTPConfig)
  ftp.ls(conf.remoteFolder, (err, fileList) => {
    if (err) return console.error(err)

    for (let i=0; i<fileList.length; i++){
      file = fileList[i]
      new JSFTP(conf.FTPConfig).get(file.name, `./Downloaded/${file.name}`, err => {
        if (err) return console.error(err)
        console.log(`${file.name} copied.`)
      })
    }
  })

＆＃13;

但是我建议使用某种流控制库，例如async或使用基于promise的解决方案，因为它可能更容易管理。

使用我提到的async模块，在类似的解决方案上也存在类似的问题：Downloading multiple file from ftp site using node js

节点FTP：循环内的多个异步调用

1 个答案: