在Swift 3中使用Stream打开到SMTP服务器的套接字连接

import Foundation

var inputStream: InputStream?
var outputStream: OutputStream?
Stream.getStreamsToHost(withName: "smtp.example.com", port: 25, inputStream: &inputStream, outputStream: &outputStream)

inputStream?.open()
outputStream?.open()

let message = "Hello, SMTP server!"
let data = message.data(using: .utf8)!
outputStream?.write((data as NSData).bytes.bindMemory(to: UInt8.self, capacity: data.count), maxLength: data.count)

var buffer = [UInt8](repeating: 0, count: 1024)
let bytesRead = inputStream?.read(&buffer, maxLength: buffer.count)
if let message = String(bytes: buffer, encoding: .utf8) {
    print("Received message: \(message)")
}

inputStream?.close()
outputStream?.close()