Hololens开发笔记：UDP接收数据

Hololens的应用需要与其他设备通信的时候，UDP是比较方便的一种方式，Unity3d 2017.3 C#开发的时候可以用Windows.Networking.Sockets.DatagramSocket 类来接收、发送UDP消息，简单快捷。

.net 的System.net.Socket对象应该也可以，但是只支持部分方法，一开始没走通所以我没继续测试下去。

开发的时候注意两个地方：

1、DatagramSocket.MessageReceived 事件不在主线程运行，所以在这个事件中不能操作UI的东西，比如给文本框赋值，否则报错。

2、Unity Build的时候Player Settings要勾选 PrivateNetworkClientServer，注意跟InternetClientServer不一样。因为我是在局域网测试，一开始只是勾选了InternetClientServer，结果无法接收消息。

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下面是网上找的一个UDP收发消息的类：

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...");

        /**
         *关键点一：创建使用UDP的网络通信对象:DatagramSocket，然后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);
            /**
             * 关键点二：绑定IP和监听端口，IP如果传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()
    {
        /**
         * 关键点四：由主线程触发事件，避免外面调用的类可能出错。
         */
        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();

        /**
         * 关键点三：接收到数据用事件发送出去，这里只是把触发事件的代码放到队列ExecuteOnMainThread中。
         * 是因为接收函数是多线程的，跟Unity主线程不一样，自己开发的时候如果在这里给文本框赋值会报错！
         */
        if (ExecuteOnMainThread.Count == 0)
        {
            ExecuteOnMainThread.Enqueue(() =>
            {
                Debug.Log("ENQEUED ");
                if (udpEvent != null)
                    udpEvent.Invoke(args.RemoteAddress.DisplayName, internalPort, msgData);
            });
        }
    }

#endif
}

　　

然后是Player Settings截图：