followed docs on server setup

server/.gitignore

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+bin
+obj

server/Lib.cs

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+using SpacetimeDB;
+
+public static partial class Module
+{
+    [Table(Name = "User", Public = true)]
+    public partial class User
+    {
+        [PrimaryKey]
+        public Identity Identity;
+        public string? Name;
+        public bool Online;
+    }
+
+    [Table(Name = "Message", Public = true)]
+    public partial class Message
+    {
+        public Identity Sender;
+        public Timestamp Sent;
+        public string Text = "";
+    }
+
+    [Reducer]
+    public static void SetName(ReducerContext ctx, string name)
+    {
+        name = ValidateName(name);
+
+        var user = ctx.Db.User.Identity.Find(ctx.Sender);
+        if (user is not null)
+        {
+            user.Name = name;
+            ctx.Db.User.Identity.Update(user);
+        }
+    }
+
+    /// Takes a name and checks if it's acceptable as a user's name.
+    private static string ValidateName(string name)
+    {
+        if (string.IsNullOrEmpty(name))
+        {
+            throw new Exception("Names must not be empty");
+        }
+        return name;
+    }
+
+    [Reducer]
+    public static void SendMessage(ReducerContext ctx, string text)
+    {
+        text = ValidateMessage(text);
+        Log.Info(text);
+        ctx.Db.Message.Insert(
+            new Message
+            {
+                Sender = ctx.Sender,
+                Text = text,
+                Sent = ctx.Timestamp,
+            }
+        );
+    }
+
+    /// Takes a message's text and checks if it's acceptable to send.
+    private static string ValidateMessage(string text)
+    {
+        if (string.IsNullOrEmpty(text))
+        {
+            throw new ArgumentException("Messages must not be empty");
+        }
+        return text;
+    }
+
+    [Reducer(ReducerKind.ClientConnected)]
+    public static void ClientConnected(ReducerContext ctx)
+    {
+        Log.Info($"Connect {ctx.Sender}");
+        var user = ctx.Db.User.Identity.Find(ctx.Sender);
+
+        if (user is not null)
+        {
+            // If this is a returning user, i.e., we already have a `User` with this `Identity`,
+            // set `Online: true`, but leave `Name` and `Identity` unchanged.
+            user.Online = true;
+            ctx.Db.User.Identity.Update(user);
+        }
+        else
+        {
+            // If this is a new user, create a `User` object for the `Identity`,
+            // which is online, but hasn't set a name.
+            ctx.Db.User.Insert(
+                new User
+                {
+                    Name = null,
+                    Identity = ctx.Sender,
+                    Online = true,
+                }
+            );
+        }
+    }
+
+    [Reducer(ReducerKind.ClientDisconnected)]
+    public static void ClientDisconnected(ReducerContext ctx)
+    {
+        var user = ctx.Db.User.Identity.Find(ctx.Sender);
+
+        if (user is not null)
+        {
+            // This user should exist, so set `Online: false`.
+            user.Online = false;
+            ctx.Db.User.Identity.Update(user);
+        }
+        else
+        {
+            // User does not exist, log warning
+            Log.Warn("Warning: No user found for disconnected client.");
+        }
+    }
+}
+

server/StdbModule.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <RuntimeIdentifier>wasi-wasm</RuntimeIdentifier>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="SpacetimeDB.Runtime" Version="1.1.*" />
+  </ItemGroup>
+
+</Project>

server/global.json

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+{
+  "sdk": {
+    "version": "8.0.400",
+    "rollForward": "latestMinor"
+  }
+}