参考 https://www.cnblogs.com/Jason-c/p/11117002.html
https://segmentfault.com/a/1190000014582485?utm_source=tag-newest
微软官方文档 ClientWebSocket类

WebSocket客户端，用来发送或接收WebSocket消息。如果你的服务所在的域是HTTPS的，那么使用的WebSocket协议也必须是wss而不是ws

示例：

using System;
using System.Collections;
using System.Collections.Generic;
using System.Net.WebSockets;
using System.Threading;
using System.Text;
using UnityEngine;

/// <summary>
/// 封装WebSocket
/// </summary>
public sealed class WebSocketWrap
{
    //连接状态改变
    public Action<WebSocketState> OnWebSocketState;
    //连接失败
    public Action OnConnectError;
    //数据返回
    public Action<string> OnMessage;

    private ClientWebSocket ws;
    private CancellationToken ct;

    // 是否已连接上
    public bool IsOpen
    {
        get
        {
            if (ws == null)
                return false;
            return ws.State == WebSocketState.Open;
        }
    }

    // 是否正在连接中...
    public bool IsConnecting
    {
        get
        {
            if (ws == null)
                return false;
            return ws.State == WebSocketState.Connecting;
        }
    }

    //uri: 例如 ws://192.168.1.155:8800
    public async void Connect(string uri)
    {
        try
        {
            if (ws != null &&
                (ws.State == WebSocketState.Connecting ||
                ws.State == WebSocketState.Open))
                return;

            Debug.LogFormat("[WebSocket] 开始连接 {0}", uri);
            ws = new ClientWebSocket();
            ct = new CancellationToken();
            Uri url = new Uri(uri);
            await ws.ConnectAsync(url, ct);

            if (OnWebSocketState != null)
                OnWebSocketState(ws.State);

            int capacity = 1024*1024;//缓冲区大小 1kb
            byte[] array = new byte[capacity];
            var buffer = new ArraySegment<byte>(array);
            List<byte> receiveList = new List<byte>();
            WebSocketReceiveResult result;
            
            while (true)
            {
                receiveList.Clear();
                do
                {
                    //接受数据
                    result = await ws.ReceiveAsync(buffer, CancellationToken.None);
                    //读取数据块
                    byte[] block = new byte[result.Count];
                    Buffer.BlockCopy(buffer.Array, 0, block, 0, block.Length);
                    receiveList.AddRange(block);
                } while (!result.EndOfMessage);//判断消息是否接收完毕

                byte[] bytes = receiveList.ToArray();
                string str = Encoding.UTF8.GetString(bytes);

                if (OnMessage != null)
                    OnMessage(str);
            }
        }
        catch (Exception ex)
        {
            Debug.LogErrorFormat("[WebSocket] {0}\nCloseStatus: {1}\nCloseStatusDescription: {2}", ex.Message, ws.CloseStatus, ws.CloseStatusDescription);
            if (OnConnectError != null)
                OnConnectError();
        }
        finally
        {
            if (ws != null)
                ws.Dispose();
            ws = null;
            Debug.Log("WebSocket Dispose!");
        }
    }

    // 发送心跳
    public void SendHeartBeat()
    {
        if (ws == null || ws.State != WebSocketState.Open)
            return;
        Debug.Log("发送心跳包");
        ws.SendAsync(new ArraySegment<byte>(Encoding.UTF8.GetBytes("{\"id\":1000}")), WebSocketMessageType.Text, true, ct);
    }

    // 发送数据
    public void Send(int id, string data)
    {
        if (ws == null || ws.State != WebSocketState.Open)
        {
            Debug.LogErrorFormat("[WebSocket] 发送数据失败，未连接上服务器。");
            return;
        }
        Debug.LogFormat("send protocol: {0}", id);
        WebDataStructure wds = new WebDataStructure();
        wds.id = id;
        wds.data = data;
        string json = JsonUtility.ToJson(wds);
        ws.SendAsync(new ArraySegment<byte>(Encoding.UTF8.GetBytes(json)), WebSocketMessageType.Text, true, ct);
    }

    //中止WebSocket连接并取消任何挂起的IO操作
    public void Abort()
    {
        if (ws == null)
            return;
        ws.Abort();
    }
}

public class WebDataStructure
{
    public int id;
    public string data; //json串
}