yep

Shogi.Api/Controllers/SessionsController.cs

@@ -77,6 +77,11 @@ public class SessionsController : ControllerBase
         return Ok(await this.queryRespository.ReadSessionPlayerCount(this.User.GetShogiUserId()));
     }
 
+    /// <summary>
+    /// Fetch the session and latest board state. Also subscribe the user to socket events for this session.
+    /// </summary>
+    /// <param name="name"></param>
+    /// <returns></returns>
     [HttpGet("{name}")]
     public async Task<ActionResult<ReadSessionResponse>> GetSession(string name)
     {
@@ -113,6 +118,7 @@ public class SessionsController : ControllerBase
             session.AddPlayer2(User.GetShogiUserId());
 
             await sessionRepository.SetPlayer2(name, User.GetShogiUserId());
+            await communicationManager.BroadcastToAll(new SessionJoinedByPlayerSocketMessage());
             return this.Ok();
         }
         return this.Conflict("This game already has two players.");
@@ -144,6 +150,8 @@ public class SessionsController : ControllerBase
             return this.Conflict(e.Message);
         }
         await sessionRepository.CreateMove(sessionName, command);
+
+        // Send socket message to both players so their clients know that new board state is available.
         await communicationManager.BroadcastToPlayers(
           new PlayerHasMovedMessage
           {

Shogi.Api/Controllers/UserController.cs

@@ -14,60 +14,68 @@ namespace Shogi.Api.Controllers;
 [Authorize]
 public class UserController : ControllerBase
 {
-	private readonly ISocketTokenCache tokenCache;
-	private readonly ISocketConnectionManager connectionManager;
-	private readonly IUserRepository userRepository;
-	private readonly IShogiUserClaimsTransformer claimsTransformation;
-	private readonly AuthenticationProperties authenticationProps;
+    private readonly ISocketTokenCache tokenCache;
+    private readonly ISocketConnectionManager connectionManager;
+    private readonly IUserRepository userRepository;
+    private readonly IShogiUserClaimsTransformer claimsTransformation;
+    private readonly AuthenticationProperties authenticationProps;
 
-	public UserController(
-		ILogger<UserController> logger,
-		ISocketTokenCache tokenCache,
-		ISocketConnectionManager connectionManager,
-		IUserRepository userRepository,
-		IShogiUserClaimsTransformer claimsTransformation)
-	{
-		this.tokenCache = tokenCache;
-		this.connectionManager = connectionManager;
-		this.userRepository = userRepository;
-		this.claimsTransformation = claimsTransformation;
-		authenticationProps = new AuthenticationProperties
-		{
-			AllowRefresh = true,
-			IsPersistent = true
-		};
-	}
+    public UserController(
+        ILogger<UserController> logger,
+        ISocketTokenCache tokenCache,
+        ISocketConnectionManager connectionManager,
+        IUserRepository userRepository,
+        IShogiUserClaimsTransformer claimsTransformation)
+    {
+        this.tokenCache = tokenCache;
+        this.connectionManager = connectionManager;
+        this.userRepository = userRepository;
+        this.claimsTransformation = claimsTransformation;
+        authenticationProps = new AuthenticationProperties
+        {
+            AllowRefresh = true,
+            IsPersistent = true
+        };
+    }
 
-	[HttpGet("Token")]
-	public ActionResult<CreateTokenResponse> GetWebSocketToken()
-	{
-		var userId = User.GetShogiUserId();
-		var displayName = User.GetShogiUserDisplayname();
+    [HttpGet("Token")]
+    public ActionResult<CreateTokenResponse> GetWebSocketToken()
+    {
+        var userId = User.GetShogiUserId();
+        var displayName = User.GetShogiUserDisplayname();
 
-		var token = tokenCache.GenerateToken(userId);
-		return new CreateTokenResponse
-		{
-			DisplayName = displayName,
-			OneTimeToken = token,
-			UserId = userId
-		};
-	}
+        var token = tokenCache.GenerateToken(userId);
+        return new CreateTokenResponse
+        {
+            DisplayName = displayName,
+            OneTimeToken = token,
+            UserId = userId
+        };
+    }
 
-	[AllowAnonymous]
-	[HttpGet("LoginAsGuest")]
-	public async Task<IActionResult> GuestLogin()
-	{
-		var principal = await this.claimsTransformation.CreateClaimsFromGuestPrincipal(User);
-		if (principal != null)
-		{
-			await HttpContext.SignInAsync(
-				CookieAuthenticationDefaults.AuthenticationScheme,
-				principal,
-				authenticationProps
-			);
-		}
-		return Ok();
-	}
+    /// <summary>
+    /// </summary>
+    /// <param name="returnUrl">Used by cookie authentication.</param>
+    /// <returns></returns>
+    [AllowAnonymous]
+    [HttpGet("LoginAsGuest")]
+    public async Task<IActionResult> GuestLogin([FromQuery] string returnUrl)
+    {
+        var principal = await this.claimsTransformation.CreateClaimsFromGuestPrincipal(User);
+        if (principal != null)
+        {
+            await HttpContext.SignInAsync(
+                CookieAuthenticationDefaults.AuthenticationScheme,
+                principal,
+                authenticationProps
+            );
+        }
+        if (!string.IsNullOrWhiteSpace(returnUrl))
+        {
+            return Redirect(returnUrl);
+        }
+        return Ok();
+    }
 
     [HttpPut("GuestLogout")]
     public async Task<IActionResult> GuestLogout()