节点FTP:循环中的多个异步调用

Question

我知道这是我已经进入的一些异步难题，但是我正在尝试下载多个文件，从npm的各种FTP软件包的.list方法中进行回调。p>所以类似的东西（注意：JSFTP这里只是node-ftp周围的包装器，我对此有同样的问题）：

  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.`)
      })
    }
  })

如果我不使用循环而只下载一个文件，则一切正常。但是，有了循环，我不断遇到以下错误，但我没有得到任何文件（一个或两个空的文件占位符除外）：

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

看起来它在循环中启动了我所有的.get调用（显然没有等待任何一个都可以完成，这很好），但是随后无法实际执行所有操作。他们不仅应该并行，异步运行吗？

{ Error: 503 Bad sequence of commands.
    at Ftp.parse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:257:11)
    at Ftp.parseResponse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:174:8)
    at Stream.<anonymous> (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:GitSenecaFTPFTPMonitornode_modulesduplexerindex.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:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:257:11)
    at Ftp.parseResponse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:174:8)
    at Stream.<anonymous> (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:GitSenecaFTPFTPMonitornode_modulesduplexerindex.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:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:257:11)
    at Ftp.parseResponse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:174:8)
    at Stream.<anonymous> (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:GitSenecaFTPFTPMonitornode_modulesduplexerindex.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:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:257:11)
    at Ftp.parseResponse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:174:8)
    at Stream.<anonymous> (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:GitSenecaFTPFTPMonitornode_modulesduplexerindex.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:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:257:11)
    at Ftp.parseResponse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:174:8)
    at Stream.<anonymous> (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:GitSenecaFTPFTPMonitornode_modulesduplexerindex.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:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:257:11)
    at Ftp.parseResponse (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:174:8)
    at Stream.<anonymous> (C:GitSenecaFTPFTPMonitornode_modulesjsftplibjsftp.js:146:24)
    at emitOne (events.js:96:13)
    at Stream.emit (events.js:188:7)
    at ResponseParser.reemit (C:GitSenecaFTPFTPMonitornode_modulesduplexerindex.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

查看了JSFTP的源后，似乎是创建一个连接，仅使用一个套接字：https：//github.com/sergi/sergi/jsftp/jsftp/blob/master/master/lib/jsftp.js＃l120

这意味着它不会为每个命令创建一个新连接，而是使用单个连接来发送命令。基本上，您如何通过为要上传的每个文件创建一个新的SFTP实例来规避这一点。

基本上将代码重新加工到此：

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.`)
      })
    }
  })

但是，我建议使用某种流控制库，例如async或使用基于承诺的解决方案，因为它可能更易于管理。

使用我提到的async模块，也有类似的问题，因此使用节点JS