Hololens開發筆記：UDP接收數據

Hololens的應用須要與其餘設備通訊的時候，UDP是比較方便的一種方式，Unity3d 2017.3 C#開發的時候能夠用Windows.Networking.Sockets.DatagramSocket 類來接收、發送UDP消息，簡單快捷。

.net 的System.net.Socket對象應該也能夠，可是隻支持部分方法，一開始沒走通因此我沒繼續測試下去。

開發的時候注意兩個地方：

一、DatagramSocket.MessageReceived 事件不在主線程運行，因此在這個事件中不能操做UI的東西，好比給文本框賦值，不然報錯。

二、Unity Build的時候Player Settings要勾選 PrivateNetworkClientServer，注意跟InternetClientServer不同。由於我是在局域網測試，一開始只是勾選了InternetClientServer，結果沒法接收消息。

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下面是網上找的一個UDP收發消息的類：

using UnityEngine;
using System;
using System.IO;
using System.Text;
using System.Linq;
using HoloToolkit.Unity;
using System.Collections.Generic;
using UnityEngine.Events;

#if !UNITY_EDITOR
using Windows.Networking.Sockets;
using Windows.Networking.Connectivity;
using Windows.Networking;
#endif

[System.Serializable]
public class UDPMessageEvent : UnityEvent<string, string, byte[]>
{

}

public class UDPCommunication : Singleton<UDPCommunication>
{
    [Tooltip("port to listen for incoming data")]
    public string internalPort = "12345";

    [Tooltip("IP-Address for sending")]
    public string externalIP = "192.168.17.110";

    [Tooltip("Port for sending")]
    public string externalPort = "12346";

    [Tooltip("Send a message at Startup")]
    public bool sendPingAtStart = true;

    [Tooltip("Conten of Ping")]
    public string PingMessage = "hello";

    [Tooltip("Function to invoke at incoming packet")]
    public UDPMessageEvent udpEvent = null;

    private readonly Queue<Action> ExecuteOnMainThread = new Queue<Action>();


#if !UNITY_EDITOR

    //we've got a message (data[]) from (host) in case of not assigned an event
    void UDPMessageReceived(string host, string port, byte[] data)
    {
        Debug.Log("GOT MESSAGE FROM: " + host + " on port " + port + " " + data.Length.ToString() + " bytes ");
    }

    //Send an UDP-Packet
    public async void SendUDPMessage(string HostIP, string HostPort, byte[] data)
    {
        await _SendUDPMessage(HostIP, HostPort, data);
    }



    DatagramSocket socket;

    async void Start()
    {
        if (udpEvent == null)
        {
            udpEvent = new UDPMessageEvent();
            udpEvent.AddListener(UDPMessageReceived);
        }


        Debug.Log("Waiting for a connection...");

        /**
         *關鍵點一：建立使用UDP的網絡通訊對象:DatagramSocket，而後添加接收消息的事件MessageReceived
         */
        socket = new DatagramSocket();
        socket.MessageReceived += Socket_MessageReceived;

        HostName IP = null;
        try
        {
            var icp = NetworkInformation.GetInternetConnectionProfile();

            IP = Windows.Networking.Connectivity.NetworkInformation.GetHostNames()
            .SingleOrDefault(
                hn =>
                    hn.IPInformation?.NetworkAdapter != null && hn.IPInformation.NetworkAdapter.NetworkAdapterId
                    == icp.NetworkAdapter.NetworkAdapterId);
            /**
             * 關鍵點二：綁定IP和監聽端口，IP若是傳null好像不行。
             */
            await socket.BindEndpointAsync(IP, internalPort);
        }
        catch (Exception e)
        {
            Debug.Log(e.ToString());
            Debug.Log(SocketError.GetStatus(e.HResult).ToString());
            return;
        }

        if (sendPingAtStart)
            SendUDPMessage(externalIP, externalPort, Encoding.UTF8.GetBytes(PingMessage));

    }




    private async System.Threading.Tasks.Task _SendUDPMessage(string externalIP, string externalPort, byte[] data)
    {
        using (var stream = await socket.GetOutputStreamAsync(new Windows.Networking.HostName(externalIP), externalPort))
        {
            using (var writer = new Windows.Storage.Streams.DataWriter(stream))
            {
                writer.WriteBytes(data);
                await writer.StoreAsync();

            }
        }
    }


#else
    // to make Unity-Editor happy :-)
    void Start()
    {

    }

    public void SendUDPMessage(string HostIP, string HostPort, byte[] data)
    {

    }

#endif


    static MemoryStream ToMemoryStream(Stream input)
    {
        try
        {                                         // Read and write in
            byte[] block = new byte[0x1000];       // blocks of 4K.
            MemoryStream ms = new MemoryStream();
            while (true)
            {
                int bytesRead = input.Read(block, 0, block.Length);
                if (bytesRead == 0) return ms;
                ms.Write(block, 0, bytesRead);
            }
        }
        finally { }
    }

    // Update is called once per frame
    void Update()
    {
        /**
         * 關鍵點四：由主線程觸發事件，避免外面調用的類可能出錯。
         */
        while (ExecuteOnMainThread.Count > 0)
        {
            ExecuteOnMainThread.Dequeue().Invoke();

        }
    }

#if !UNITY_EDITOR
    private void Socket_MessageReceived(Windows.Networking.Sockets.DatagramSocket sender,
        Windows.Networking.Sockets.DatagramSocketMessageReceivedEventArgs args)
    {
        Debug.Log("GOT MESSAGE FROM: " + args.RemoteAddress.DisplayName);
        //Read the message that was received from the UDP  client.
        Stream streamIn = args.GetDataStream().AsStreamForRead();
        MemoryStream ms = ToMemoryStream(streamIn);
        byte[] msgData = ms.ToArray();

        /**
         * 關鍵點三：接收到數據用事件發送出去，這裏只是把觸發事件的代碼放到隊列ExecuteOnMainThread中。
         * 是由於接收函數是多線程的，跟Unity主線程不同，本身開發的時候若是在這裏給文本框賦值會報錯！
         */
        if (ExecuteOnMainThread.Count == 0)
        {
            ExecuteOnMainThread.Enqueue(() =>
            {
                Debug.Log("ENQEUED ");
                if (udpEvent != null)
                    udpEvent.Invoke(args.RemoteAddress.DisplayName, internalPort, msgData);
            });
        }
    }


#endif
}

　　

而後是Player Settings截圖：