MonitoringFramer, still don't know what's the best way to insert into NIOTransportServices.

gistfile1.swift

// First, define our monitoring framer
class MonitoringFramer: NWProtocolFramerImplementation {
  func wakeup(framer: NWProtocolFramer.Instance) {
    
  }
  
  func stop(framer: NWProtocolFramer.Instance) -> Bool {
    return true
  }
  
  func cleanup(framer: NWProtocolFramer.Instance) {
    
  }
  
  // Protocol definition
  static let definition = NWProtocolFramer.Definition(implementation: MonitoringFramer.self)
  
  // Required protocol identifier
  static var label: String { return "MonitoringFramer" }
  
  // Each connection needs its own instance of the framer
  required init(framer: NWProtocolFramer.Instance) {
      self.framerInstance = framer
  }
  
  private let framerInstance: NWProtocolFramer.Instance
  
  // Start point for monitoring outgoing messages
  func start(framer: NWProtocolFramer.Instance) -> NWProtocolFramer.StartResult {
      return .ready
  }
  
  // Handle incoming messages
  func handleInput(framer: NWProtocolFramer.Instance) -> Int {
    _ = framer.parseInput(minimumIncompleteLength: 1, maximumLength: 65535) { buffer, endOfMessage in
      if let buffer = buffer {
        _ = framer.deliverInputNoCopy(length: buffer.count, message: .init(instance: framer), isComplete: endOfMessage)
        logReceived(messageLength: buffer.count)
      }
      return 0
    }
    return 0
  }
  
  // Handle outgoing messages
  func handleOutput(framer: NWProtocolFramer.Instance, message: NWProtocolFramer.Message, messageLength: Int, isComplete: Bool) {
    // Get data the application wants to send
    try? framer.writeOutputNoCopy(length: messageLength)
    logSent(messageLength: messageLength)
  }
    
    // MARK: - Logging Methods
    
  private func logSent(messageLength: Int) {
    let timestamp = Date()
    print("[\(timestamp)] SENT [\(messageLength) bytes]")
  }
    
  private func logReceived(messageLength: Int) {
    let timestamp = Date()
    print("[\(timestamp)] RECEIVED [\(messageLength) bytes]")
  }
}