It‘s like JSON.
but fast and small.

MessagePack is an efficient binary serialization format. It lets you exchange data among multiple languages like JSON. But it‘s faster and smaller. Small integers are encoded into a single byte, and typical short strings require only one extra byte in addition to the strings themselves.

MessagePack 是一個高效的二進制序列化格式。它讓你像JSON一樣可以在各種語言之間交換數據。但是它比JSON更快、更小。小的整數會被編碼成一個字節，短的字符串僅僅只需要比它的長度多一字節的大小。

在 SignalR 中使用 MessagePack 也很簡單：

public void ConfigureServices(IServiceCollection services)
        {
            //自定義配置
            services.Configure<DbSetting>(Configuration.GetSection("
 
ConnectionStrings"));

            //https://docs.microsoft.com/en-us/aspnet/core/security/gdpr?view=aspnetcore-2.1
            services.Configure<CookiePolicyOptions>(options =>
            {
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy 
 
= SameSiteMode.None;
            });

            //添加 Hangfire 服務
            services.AddHangfire(config => config.UseRedisStorage(Redis));
            // services.AddHangfire(config => config.UseSqlServerStorage("<connection string>"));

            //添加 Cookie 中間件
            services.AddAuthentication(sharedOptions =>
            {
                sharedOptions.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                // sharedOptions.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
            })

            //.AddAzureAdB2C(opts => Configuration.Bind("AzureAdB2C", opts))
            .AddCookie(opts =>
            {
                opts.LoginPath = new PathString("/account/login");
                opts.AccessDeniedPath = new PathString("/account/denied");
            });

            services.AddSignalR(options =>
            {
                //Faster pings for testing
                options.KeepAliveInterval = TimeSpan.FromSeconds(5);
            })
            .AddMessagePackProtocol(options =>
            {
                options.FormatterResolvers = new List<MessagePack.IFormatterResolver>()
                {
                    MessagePack.Resolvers.StandardResolver.Instance
                };
            })
            .AddRedis(Configuration.GetConnectionString("Redis"));

            //返回大小寫問題
            services.AddMvc()
                    .AddJsonOptions(option => option.SerializerSettings.ContractResolver = new Newtonsoft.Json.Serialization.DefaultContractResolver());
        }

.NET 客戶端

var hubConnection = new HubConnectionBuilder()
                        .WithUrl("/chatHub")
                        .AddMessagePackProtocol()
                        .Build();

JavaScript 客戶端

npm install @aspnet/signalr-protocol-msgpack

<script src="~/lib/signalr/signalr.js"></script>
<script src="~/lib/msgpack5/msgpack5.js"></script>
<script src="~/lib/signalr/signalr-protocol-msgpack.js"></script>

const connection = new signalR.HubConnectionBuilder()
                              .withUrl("/hqHub")
                              .withHubProtocol(new signalR.protocols.msgpack.MessagePackHubProtocol())
                              .build();

REFER:
https://docs.microsoft.com/en-us/aspnet/core/signalr/messagepackhubprotocol?view=aspnetcore-2.1
https://damienbod.com/2018/03/19/using-message-pack-with-asp-net-core-signalr/

ASP.NET Core SignalR 中使用 MessagePack