[Unity]非同期処理(Task)の利用例(UDP送受信，SerialPortのRead) ref: https://qiita.com/togucchi/items/45cf6e65c883e6f47d3d

file0.cs

using UnityEngine;
using System.Collections;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

public class UdpServer : MonoBehaviour
{
    // UnityEventの引数指定用のダミークラス
    public class ReceivedCallback : UnityEngine.Events.UnityEvent<string>
    {
    }

    // データを受信したときに発火されるイベント
    public static ReceivedCallback OnReceivedEvent = new ReceivedCallback();

    [SerializeField]
    int port = 22222;
    static UdpClient udp;

    Task receiveTask;

    bool isRunning = false;

    public bool IsRunning
    {
        get
        {
            return isRunning;
        }
    }

    void Awake ()
    {
        udp = new UdpClient(port);
        // udp.Client.ReceiveTimeout = 1000;

        OpenServer();
    }

    void OnDisable()
    {  
        CloseServer();
    }

    void OnEnable()
    {
        if(!isRunning)
        {
            OpenServer();
        }
    }

    public void OpenServer()
    {
        if(isRunning) return;
        isRunning = true;
        receiveTask = DataReceiveTask();
    }

    public void CloseServer()
    {
        if(!isRunning) return;

        isRunning = false;

        // isRunningをfalseにするとTaskが止まるのでそれを待つ
        if(receiveTask != null && receiveTask.Status == TaskStatus.Running)
        {
            receiveTask.Wait();
        }

    }

    async Task DataReceiveTask()
    {
        await Task.Run(() =>
        {
            while(isRunning)
            {
                //Debug.Log("TEST");
                IPEndPoint remoteEP = null;
                byte[] data = udp.Receive(ref remoteEP);
                string text = Encoding.ASCII.GetString(data);

                // 登録したイベントを発火
                OnReceivedEvent.Invoke(text);
            }
        });
    }     
}

file1.cs

using UnityEngine;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

public class UdpSender : MonoBehaviour
{
    // broadcast address
    public string host = "192.168.0.255";
    public int port = 3333;
    private UdpClient client;

    bool isConnect = false;

    void Start ()
    {
        client = new UdpClient();
    }

    public void ConnectClient(string host, int port)
    {
        if(isConnect)
        {
            return;
        }
        this.host = host;
        this.port = port;
        client.Connect(host, port);
    }

    public void CloseClient()
    {
        if(!isConnect)
        {
            return;
        }
        client.Close();
    }

    void Test_Send()
    {
        byte[] dgram = Encoding.UTF8.GetBytes("hello!");
        SendData(dgram);
    }

    public async Task SendData(string json)
    {
        await Task.Run(() => {
            byte[] dgram = Encoding.UTF8.GetBytes(json);
            client.Send(dgram, dgram.Length);
        });
    }

    public async Task SendData(byte[] dgram)
    {
        await Task.Run(() => {
            client.Send(dgram, dgram.Length);
        });
    }

    void OnDisable()
    {
        client.Close();
    }
}

file2.cs

using UnityEngine;
using UnityEngine.Events;
using System.Collections;
using System.IO.Ports;
using System.Threading;
using System.Threading.Tasks;

public class SerialPortHandler : MonoBehaviour
{
    [System.Serializable]
    public class DataCallback : UnityEvent<string>
    {

    }
    public static DataCallback OnDataReceived = new DataCallback();

    // ボーレート (bit/sec)
    public int baudRate = 115200;
    public bool isDebug = false;

    string currentPortName = null;
    bool isRunning = false;

    SerialPort serialPort;
    Task task;

    void Start()
    {
        // Debug用
        if(isDebug && currentPortName != null)
        { 
            Open(currentPortName);
        }
    }

    void OnDestroy()
    {
        Close();
    }

    void OnEnable()
    {
        if(currentPortName != null && !isRunning)
        {
            Open(currentPortName);
        }
    }

    void OnDisable()
    {
        Close();
    }

    // ポート名を指定してSerialPortを開く
    public void Open(string portName)
    {
        if(isRunning) return;

        currentPortName = portName;

        serialPort = new SerialPort(portName, baudRate, Parity.None, 8, StopBits.One);
        serialPort.Open();

        isRunning = true;

        task = ReadAsync();
    }

    public void Close()
    {
        if(!isRunning) return;

        isRunning = false;

        // タスクの終了待ち
        if (task != null && task.Status == TaskStatus.Running)
        {
            task.Wait();
        }

        // タスクが終了してからSerialPortを閉じる
        if (serialPort != null && serialPort.IsOpen)
        {
            serialPort.Close();
            serialPort.Dispose();
        }
    }

    async Task ReadAsync()
    {
        await Task.Run(() => {
            while (isRunning && serialPort != null && serialPort.IsOpen)
            {
                try
                {
                    string message = serialPort.ReadLine();
                  // Debug.LogWarning(message);
                    OnDataReceived.Invoke(message);
                }
                catch (System.Exception e)
                {
                    Debug.LogWarning(e.Message);
                }
            }
        });
    }
}

SerialPortHandler.cs

using UnityEngine;
using UnityEngine.Events;
using System.Collections;
using System.IO.Ports;
using System.Threading;
using System.Threading.Tasks;

public class SerialPortHandler : MonoBehaviour
{
    [System.Serializable]
    public class DataCallback : UnityEvent<string>
    {

    }
    public static DataCallback OnDataReceived = new DataCallback();

    // ボーレート (bit/sec)
    public int baudRate = 115200;
    public bool isDebug = false;

    string currentPortName = null;
    bool isRunning = false;

    SerialPort serialPort;
    Task task;

    void Start()
    {
        // Debug用
        if(isDebug && currentPortName != null)
        { 
            Open(currentPortName);
        }
    }

    void OnDestroy()
    {
        Close();
    }

    void OnEnable()
    {
        if(currentPortName != null && isRunning)
        {
            Open(currentPortName);
        }
    }

    void OnDisable()
    {
        Close();
    }

    // ポート名を指定してSerialPortを開く
    public void Open(string portName)
    {
        if(isRunning) return;

        currentPortName = portName;

        serialPort = new SerialPort(portName, baudRate, Parity.None, 8, StopBits.One);
        serialPort.Open();

        isRunning = true;

        task = ReadAsync();
    }

    public void Close()
    {
        if(!isRunning) return;

        isRunning = false;

        // タスクの終了待ち
        if (task != null && task.Status == TaskStatus.Running)
        {
            task.Wait();
        }

        // タスクが終了してからSerialPortを閉じる
        if (serialPort != null && serialPort.IsOpen)
        {
            serialPort.Close();
            serialPort.Dispose();
        }
    }

    async Task ReadAsync()
    {
        await Task.Run(() => {
            while (isRunning && serialPort != null && serialPort.IsOpen)
            {
                try
                {
                    string message = serialPort.ReadLine();
                  // Debug.LogWarning(message);
                    OnDataReceived.Invoke(message);
                }
                catch (System.Exception e)
                {
                    Debug.LogWarning(e.Message);
                }
            }
        });
    }
}

UdpSender.cs

using UnityEngine;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

public class UdpSender : MonoBehaviour
{
    // broadcast address
    public string host = "192.168.0.255";
    public int port = 3333;
    private UdpClient client;

    bool isConnect = false;

    void Start ()
    {
        client = new UdpClient();
    }

    public void ConnectClient(string host, int port)
    {
        if(isConnect)
        {
            return;
        }
        this.host = host;
        this.port = port;
        client.Connect(host, port);
    }

    public void CloseClient()
    {
        if(!isConnect)
        {
            return;
        }
        client.Close();
    }

    void Test_Send()
    {
        byte[] dgram = Encoding.UTF8.GetBytes("hello!");
        SendData(dgram);
    }

    public async Task SendData(string json)
    {
        await Task.Run(() => {
            byte[] dgram = Encoding.UTF8.GetBytes(json);
            client.Send(dgram, dgram.Length);
        });
    }

    public async Task SendData(byte[] dgram)
    {
        await Task.Run(() => {
            client.Send(dgram, dgram.Length);
        });
    }

    void OnDisable()
    {
        client.Close();
    }
}

UdpServer.cs

using UnityEngine;
using System.Collections;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

public class UdpServer : MonoBehaviour
{
    // UnityEventの引数指定用のダミークラス
    public class ReceivedCallback : UnityEngine.Events.UnityEvent<string>
    {
    }

    // データを受信したときに発火されるイベント
    public static ReceivedCallback OnReceivedEvent = new ReceivedCallback();

    [SerializeField]
    int port = 22222;
    static UdpClient udp;

    Task receiveTask;

    bool isRunning = false;

    public bool IsRunning
    {
        get
        {
            return isRunning;
        }
    }

    void Awake ()
    {
        udp = new UdpClient(port);
        // udp.Client.ReceiveTimeout = 1000;

        OpenServer();
    }

    void OnDisable()
    {  
        CloseServer();
    }

    void OnEnable()
    {
        if(isRunning)
        {
            OpenServer();
        }
    }

    public void OpenServer()
    {
        if(isRunning) return;
        isRunning = true;
        receiveTask = DataReceiveTask();
    }

    public void CloseServer()
    {
        if(!isRunning) return;

        isRunning = false;

        // isRunningをfalseにするとTaskが止まるのでそれを待つ
        if(receiveTask != null && receiveTask.Status == TaskStatus.Running)
        {
            receiveTask.Wait();
        }

    }

    async Task DataReceiveTask()
    {
        await Task.Run(() =>
        {
            while(isRunning)
            {
                //Debug.Log("TEST");
                IPEndPoint remoteEP = null;
                byte[] data = udp.Receive(ref remoteEP);
                string text = Encoding.ASCII.GetString(data);

                // 登録したイベントを発火
                OnReceivedEvent.Invoke(text);
            }
        });
    }     
}