在 Swift 中实现 FTP 文件传输（STOR）？

Question

我正在开发一个用 Swift 编写的客户端 iOS 应用，它允许用户在 FTP 服务器 上传输文件。我知道 Apple 提供了 API 来执行此操作，但它们自 2016 年以来已被弃用，我需要一个替代方案。我也知道 FTP 不安全，但我必须这样做。我的目标是通过服务器打开一个 Socket 并向它发送命令以传输文件。我正在使用BlueSocket，但我无法得到它。这是我的代码：

do {
    let socket = try Socket.create()
                    
    try socket.connect(to: "127.0.0.1", port: 21)
    let answer = try socket.readString()
    print(answer!)
                    
    try socket.write(from: "USER test\r\n")
    let userAnswer = try socket.readString()
    print(userAnswer!)
                    
    try socket.write(from: "PASS 0000\r\n")
    let passwordAnswer = try socket.readString()
    print(passwordAnswer!)
                    
    try socket.write(from: "PASV\r\n")
    let passiveModeAnswer = try socket.readString()
    print(passiveModeAnswer!)
                    
    try socket.write(from: "STOR myFile.txt\r\n")
    let storAnswer = try socket.readString()
    print(storAnswer!)

    /* CODE FOR SENDING FILE BELOW */

} catch let error as NSError {
    print(error.debugDescription)
}

我目前正在本地服务器上工作，并且登录成功。服务器已准备好接受数据。我在控制台中看到了这个：

150 Ok to receive data.

这是我用来发送文件的代码：

guard let path = Bundle.main.path(forResource: "myFile", ofType: "txt"),
      let fileInputStream = InputStream(fileAtPath: path) 
else {
    return
}
            
fileInputStream.open()

var buffer = [UInt8](repeating: 0, count: 1024)
var bytesRead = 0
var fileData = Data()

while fileInputStream.hasBytesAvailable {
    bytesRead = fileInputStream.read(&buffer, maxLength: buffer.count)
    fileData.append(buffer, count: bytesRead)
}

try socket.write(from: fileData)
let fileAnswer = try socket.readString()
print(fileAnswer!)

fileInputStream.close()
socket.close()

执行后，我在本地服务器中看到“myFile.txt”，但它是空的。原始文件存储在 Xcode 中：它是一个 13 字节的文件（一个简单的文本文件）。我看到一个断点，bytesRead 更改为 13 并且 fileData 被重视。在try socket.write(from: fileData) 指令之后，我没有收到来自套接字的任何响应，但只有这个错误消息：Error code: -9982(0x-26FE), Interrupted system call。有什么遗漏或错误吗？我在实现目标方面做得很好吗？

---

正如 Martin 所说，我已经解析了 PASV 答案的结果，代码如下：

guard let path = Bundle.main.path(forResource: "myFile", ofType: "txt"),
      let fileInputStream = InputStream(fileAtPath: path) 
else {
    return
}
            
fileInputStream.open()
            
guard let pasvAnswer = passiveModeAnswer else {
    return
}
            
var editedAnswer = String(pasvAnswer.dropFirst(26))
editedAnswer = editedAnswer.replacingOccurrences(of: ")", with: "")
editedAnswer = editedAnswer.replacingOccurrences(of: "(", with: "")
editedAnswer = editedAnswer.replacingOccurrences(of: ",", with: ".")
editedAnswer = String(editedAnswer.dropLast())
let cmps = editedAnswer.components(separatedBy: ".")
            
let dataHost = cmps[0] + "." + cmps[1] + "." + cmps[2] + "." + cmps[3]
let dataPort = ((Int(cmps[4]))!<<8) + Int(cmps[5])!
            
print("dataHost: \(dataHost), dataPort: \(dataPort)")
            
try socket.write(from: "STOR myFile.txt\r\n")
let storAnswer = try socket.readString()
print(storAnswer!)
            
let dataSocket = try Socket.create()
try dataSocket.connect(to: dataHost, port: Int32(dataPort))
            
var buffer = [UInt8](repeating: 0, count: 1024)
var bytesRead = 0
var fileData = Data()

while fileInputStream.hasBytesAvailable {
    bytesRead = fileInputStream.read(&buffer, maxLength: buffer.count)
    fileData.append(buffer, count: bytesRead)
}
            
try dataSocket.write(from: fileData)
let fileAnswer = try dataSocket.readString()
print(fileAnswer!)
            
fileInputStream.close()
dataSocket.close()
socket.close()

我观察到该文件仅在我终止应用程序时才完全传输。有什么想法吗？

Answer 1

您必须解析 PASV 响应 (passiveModeAnswer)。并连接到提供的 IP 地址和端口，并将文件内容发送到新连接。