Sending audio recording to server (express api) (Iphone/watch) but data body empty

Dear community
I want to continuously record the audio for 15 seconds with the apple smartwatch (the Code for the Iphone should look pretty much the same) and send the recording each time to the express API. The post request goes through definitely since the messages from the console logs could be printed, just the data body is empty. I do not know what I have done wrongly here

Here is my Swift code:

//
//  InterfaceController.swift
//  AudioAppTest WatchKit Extension
//
//

import WatchKit
import Foundation
import AVFoundation


class InterfaceController: WKInterfaceController, AVAudioRecorderDelegate, AVAudioPlayerDelegate{


    @IBOutlet weak var recordBtn: WKInterfaceButton!
    var recordSession: AVAudioSession!
    var audioRecorder: AVAudioRecorder!
    var audioPlayer: AVAudioPlayer!
    var settings = [String : Int]()

    override func awake(withContext context: Any?) {
        super.awake(withContext: context)
        recordSession = AVAudioSession.sharedInstance()

        if(recordSession.responds(to:#selector(AVAudioSession.requestRecordPermission(_:)))){
            // configure audio settings
            AVAudioSession.sharedInstance().requestRecordPermission({(granted: Bool) -> Void in
                if granted{
                    print("Recording granted!")

                    do{
                        try self.recordSession.setCategory(.playAndRecord,mode: .default, options: [])
                        try self.recordSession.setActive(true)
                    }catch{
                        print("Audio session could not be set!")
                    }
                }else{
                    print("Recording not granted!")
                }
            })
        }

        settings = [AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
                    AVSampleRateKey: 12000,
                    AVNumberOfChannelsKey: 1,
                    AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
        ]

    }

    override func willActivate() {
        // This method is called when watch view controller is about to be visible to user
        super.willActivate()
    }

    override func didDeactivate() {
        // This method is called when watch view controller is no longer visible
        super.didDeactivate()
    }

    func getDocumentsDirectory()-> URL {
        let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        let documentDirectory = paths[0]
        return documentDirectory
    }

    func getAudioURL() -> URL {
        let filename = NSUUID().uuidString+".m4a"
        return getDocumentsDirectory().appendingPathComponent(filename)
    }

    func startRecording(){

        do{
            let audioURL = self.getAudioURL()
             print("first \(audioURL)")
            audioRecorder = try AVAudioRecorder(url:self.getAudioURL(),settings:settings)
            audioRecorder.delegate = self
            audioRecorder.record(forDuration: 15)
        }catch{
            finishRecording(success: false)
        }
    }

    func finishRecording(success: Bool){
        audioRecorder.stop()
        if success{
            print("Recorded successfully!")
        }else{
            audioRecorder = nil
            print("Recording failed!")
        }

    }

    @IBAction func recordListener() {
        print("Button clicked!")
        if audioRecorder == nil{
            self.startRecording()
        }else{
            self.finishRecording(success: true)
        }
    }

    func audioRecorderDidFinishRecording(_ recorder: AVAudioRecorder, successfully flag: Bool) {
        if !flag{
            finishRecording(success:false)
        }
        print("What is this url \(recorder.url)")
        sendAudio(audioPath: recorder.url)
        audioRecorder = nil
        startRecording()

    }

    func preparePlayer(){
        do{
            audioPlayer = try AVAudioPlayer(contentsOf: audioRecorder.url)
            audioPlayer.delegate = self
            audioPlayer.prepareToPlay()
            audioPlayer.volume = 5.0
        }catch{
            if let err = error as Error?{
                print("AVAudioPlayer error: \(err.localizedDescription)")
            }
        }
    }



    func sendAudio(audioPath: URL){
        let apiURL = URL(string:"http://147.46.215.219:8080/addAudio")
        let recordingData: Data? = try? Data(contentsOf:audioPath)
        let boundary = "---011000010111000001101001"
        let startBoundary = "--\(boundary)"
        let endingBoundary = "--\(boundary)--"

        // getting the fileName
        let urlStr = "\(audioPath)"
        let pathArr = urlStr.components(separatedBy: "/")
        let fileName = pathArr.last


        var body = Data()
        var header = "Content-Disposition: form-data; name=\"\(fileName)\"; filename=\"\(audioPath)\"\r\n"

        body.append(("\(startBoundary)\r\n" as String).data(using:.utf8)!)
        body.append((header as String).data(using:.utf8)!)
        body.append(("Content-Type: application/octet-stream\r\n\r\n" as String).data(using:.utf8)!)
        body.append(recordingData!)
        body.append(("\r\n\(endingBoundary)\r\n" as String).data(using:.utf8)!)

        var request = URLRequest(url:apiURL!)
            request.httpMethod = "POST"
            request.setValue("multipart/form-data;boundary=\(boundary)",forHTTPHeaderField: "Content-Type")
            request.setValue("application/json",forHTTPHeaderField: "Accept")

        let session = URLSession.shared

        let task = session.dataTask(with: request){ (data, response,error) in
            print("Upload complete!")

            if let error = error{
                print("error: \(error)")
                return
            }

            guard let response = response as? HTTPURLResponse,
                (200...299).contains(response.statusCode) else {
                    print("Error on server side!")
                    return
            }

            if let mimeType = response.mimeType,
            mimeType == "audio/m4a",
            let data = data,
                let dataStr = String(data: data, encoding: .utf8){
                print("data is \(dataStr)")
            }
        }
        task.resume()

    }

  /**
    @IBAction func playPressed() {

        if audioRecorder != nil{
            if !audioRecorder.isRecording{
                preparePlayer()
                audioPlayer.play()
            }
            audioRecorder = nil
        }else{
            print("Empty file!")
        }
    }
    */

}

Here is my express code:

var express = require('express');
require('dotenv').config();
var cors = require('cors');
var mysql = require('mysql');
var bodyParser = require('body-parser');
var http = require('http');
var app = express();


app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());
app.use(bodyParser.raw({ type: 'audio/m4a', limit: '60mb' }))
app.use(cors());


app.post('/addAudio', function (req, res) {
    console.log("Audio is successfully posted!")
    console.log("Obtained audio data: ", req.body);
})

app.listen(8080, function () {
    console.log("Server is listening on port 8080!");
});

I also tried it by using the framework alamofire but both gives an empty data body. I hope you can help me out .

//
//  InterfaceController.swift
//  AudioAppTest WatchKit Extension
//
//

import WatchKit
import Foundation
import AVFoundation
import Alamofire
import SwiftyJSON

class InterfaceController: WKInterfaceController, AVAudioRecorderDelegate, AVAudioPlayerDelegate{


    @IBOutlet weak var recordBtn: WKInterfaceButton!
    var recordSession: AVAudioSession!
    var audioRecorder: AVAudioRecorder!
    var audioPlayer: AVAudioPlayer!
    var settings = [String : Int]()

    override func awake(withContext context: Any?) {
        super.awake(withContext: context)
        recordSession = AVAudioSession.sharedInstance()

        if(recordSession.responds(to:#selector(AVAudioSession.requestRecordPermission(_:)))){
            // configure audio settings
            AVAudioSession.sharedInstance().requestRecordPermission({(granted: Bool) -> Void in
                if granted{
                    print("Recording granted!")

                    do{
                        try self.recordSession.setCategory(.playAndRecord,mode: .default, options: [])
                        try self.recordSession.setActive(true)
                    }catch{
                        print("Audio session could not be set!")
                    }
                }else{
                    print("Recording not granted!")
                }
            })
        }

        settings = [AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
                    AVSampleRateKey: 12000,
                    AVNumberOfChannelsKey: 1,
                    AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
        ]

    }

    override func willActivate() {
        // This method is called when watch view controller is about to be visible to user
        super.willActivate()
    }

    override func didDeactivate() {
        // This method is called when watch view controller is no longer visible
        super.didDeactivate()
    }

    func getDocumentsDirectory()-> URL {
        let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        let documentDirectory = paths[0]
        return documentDirectory
    }

    func getAudioURL() -> URL {
        let filename = NSUUID().uuidString+".m4a"
        return getDocumentsDirectory().appendingPathComponent(filename)
    }

    func startRecording(){

        do{
            let audioURL = self.getAudioURL()
             print("first \(audioURL)")
            audioRecorder = try AVAudioRecorder(url:self.getAudioURL(),settings:settings)
            audioRecorder.delegate = self
            audioRecorder.record(forDuration: 15)
        }catch{
            finishRecording(success: false)
        }
    }

    func finishRecording(success: Bool){
        audioRecorder.stop()
        if success{
            print("Recorded successfully!")
        }else{
            audioRecorder = nil
            print("Recording failed!")
        }

    }

    @IBAction func recordListener() {
        print("Button clicked!")
        if audioRecorder == nil{
            self.startRecording()
        }else{
            self.finishRecording(success: true)
        }
    }

    func audioRecorderDidFinishRecording(_ recorder: AVAudioRecorder, successfully flag: Bool) {
        if !flag{
            finishRecording(success:false)
        }
        var studentId = "student1234"
        var date = "2020-05-13"
        print("What is this url \(recorder.url)")
        sendAudio(audioPath: recorder.url)
        audioRecorder = nil
        startRecording()

    }

    func preparePlayer(){
        do{
            audioPlayer = try AVAudioPlayer(contentsOf: audioRecorder.url)
            audioPlayer.delegate = self
            audioPlayer.prepareToPlay()
            audioPlayer.volume = 5.0
        }catch{
            if let err = error as Error?{
                print("AVAudioPlayer error: \(err.localizedDescription)")
            }
        }
    }



    func sendAudio(audioPath: URL){

        // getting fileName
               let urlStr = "\(audioPath)"
               let pathArr = urlStr.components(separatedBy: "/")
        let fileName = String(pathArr.last!)

               print("Here is the fileName: \(fileName)")

        do {
         let audioData = try Data(contentsOf: audioPath)
            AF.upload(multipartFormData: { multipartFormData in
                     multipartFormData.append(audioData, withName: fileName)
                 }, to: "http://147.46.215.219:8080/addAudio")
                     .responseJSON { response in
                         debugPrint(response)
                 }

        } catch {
         print(" not able to upload data\(error)")
        }

    }







  /**
    @IBAction func playPressed() {

        if audioRecorder != nil{
            if !audioRecorder.isRecording{
                preparePlayer()
                audioPlayer.play()
            }
            audioRecorder = nil
        }else{
            print("Empty file!")
        }
    }
    */

}