Build a Simple Chat Server With gRPC in .Net Core

public class ChatService : ChatServerBase
{
    private readonly ILogger<ChatService> _logger;

    public ChatService(ILogger<ChatService> logger)
    {
        _logger = logger;
    }

    public override Task HandleCommunication(IAsyncStreamReader<ClientMessage> requestStream, IServerStreamWriter<ServerMessage> responseStream, ServerCallContext context)
    {
        return base.HandleCommunication(requestStream, responseStream, context);
    }
}

using ChatServer.Services;
using Microsoft.AspNetCore.Server.Kestrel.Core;

var builder = WebApplication.CreateBuilder(args);


/*
// Additional configuration is required to successfully run gRPC on macOS.
// For instructions on how to configure Kestrel and gRPC clients on macOS,
// visit https://go.microsoft.com/fwlink/?linkid=2099682

   To avoid missing ALPN support issue on Mac. To work around this issue, configure Kestrel and the gRPC client to use HTTP/2 without TLS.
   You should only do this during development. Not using TLS will result in gRPC messages being sent without encryption.
   
   https://learn.microsoft.com/en-us/aspnet/core/grpc/troubleshoot?view=aspnetcore-7.0
*/
builder.WebHost.ConfigureKestrel(options =>
{
    // Setup a HTTP/2 endpoint without TLS.
    options.ListenLocalhost(50051, o => o.Protocols =
        HttpProtocols.Http2);
});


// Add services to the container.
builder.Services.AddGrpc();
builder.Services.AddSingleton<ChatRoomService>();

var app = builder.Build();

// Configure the HTTP request pipeline.
app.MapGrpcService<ChatService>();
app.MapGet("/", () => "Communication with gRPC endpoints must be made through a gRPC client. To learn how to create a client, visit: https://go.microsoft.com/fwlink/?linkid=2086909");

Console.WriteLine($"gRPC server about to listening on port:50051");

app.Run();

using System;
using ChatServer;
using Grpc.Core;
using System.Collections.Concurrent;

namespace ChatServer.Services
{
    public class ChatRoomService
    {
        private static readonly ConcurrentDictionary<string, List<ChatClient>> _chatRooms = new ConcurrentDictionary<string, List<ChatClient>>();

        /// <summary>
        /// Read a single message from the client.
        /// </summary>
        /// <exception cref="ConnectionLostException"></exception>
        /// <exception cref="TimeoutException"></exception>
        public async Task<ClientMessage> ReadMessageWithTimeoutAsync(IAsyncStreamReader<ClientMessage> requestStream, TimeSpan timeout)
        {
            CancellationTokenSource cancellationTokenSource = new();

            cancellationTokenSource.CancelAfter(timeout);

            try
            {
                bool moveNext = await requestStream.MoveNext(cancellationTokenSource.Token);

                if (moveNext == false)
                {
                    throw new Exception("connection dropped exception");
                }

                return requestStream.Current;
            }
            catch (RpcException ex) when (ex.StatusCode == StatusCode.Cancelled)
            {
                throw new TimeoutException();
            }
        }

        /// <summary>
        /// <summary>
        /// </summary>
        /// <param name="chatRoomId"></param>
        /// <param name="user"></param>
        /// <returns></returns>

        public async Task AddClientToChatRoom(string chatRoomId, ChatClient chatClient)
        {
            if (!_chatRooms.ContainsKey(chatRoomId))
            {
                _chatRooms[chatRoomId] = new List<ChatClient> { chatClient };
            }
            else
            {
                var existingUser = _chatRooms[chatRoomId].FirstOrDefault(c => c.UserName == chatClient.UserName);
                if (existingUser != null)
                {
                    // A user with the same user name already exists in the chat room
                    throw new InvalidOperationException("User with the same name already exists in the chat room");
                }
                _chatRooms[chatRoomId].Add(chatClient);
            }

            await Task.CompletedTask;
        }
        /// <summary>
        /// Broad client joined the room message.
        /// </summary>
        /// <param name="userName"></param>
        /// <param name="chatRoomId"></param>
        /// <returns></returns>
        public async Task BroadcastClientJoinedRoomMessage(string userName, string chatRoomId)
        {
            if (_chatRooms.ContainsKey(chatRoomId))
            {
                var message = new ServerMessage { UserJoined = new ServerMessageUserJoined { UserName = userName } };

                var tasks = new List<Task>();

                foreach (var stream in _chatRooms[chatRoomId])
                {
                    if (stream != null && stream != default)
                    {
                        tasks.Add(stream.StreamWriter.WriteAsync(message));
                    }
                }

                await Task.WhenAll(tasks);
            }
        }

        /// <summary>
        /// </summary>
        /// <param name="chatRoomId"></param>
        /// <param name="senderName"></param>
        /// <param name="text"></param>
        /// <returns></returns>
        public async Task BroadcastMessageToChatRoom(string chatRoomId, string senderName, string text)
        {
            if (_chatRooms.ContainsKey(chatRoomId))
            {
                var message = new ServerMessage { Chat = new ServerMessageChat { UserName = senderName, Text = text } };

                var tasks = new List<Task>();
                var streamList = _chatRooms[chatRoomId];
                foreach (var stream in _chatRooms[chatRoomId])
                {
                    //This senderName can be something of unique Id for each user.
                    if (stream != null && stream != default && stream.UserName != senderName)
                    {
                        tasks.Add(stream.StreamWriter.WriteAsync(message));
                    }
                }

                await Task.WhenAll(tasks);
            }
        }
    }

    public class ChatClient
    {
        public IServerStreamWriter<ServerMessage> StreamWriter { get; set; }
        public string UserName { get; set; }
    }
}

using System;
using ChatServer;
using Grpc.Core;

namespace ChatServer.Services
{
    public class ChatService : ChatServer.ChatServerBase
    {
        private readonly ILogger<ChatService> _logger;
        private readonly ChatRoomService _chatRoomService;

        public ChatService(ChatRoomService chatRoomService, ILogger<ChatService> logger)
        {
            _chatRoomService = chatRoomService;
            _logger = logger;
        }

        public override async Task HandleCommunication(IAsyncStreamReader<ClientMessage> requestStream, IServerStreamWriter<ServerMessage> responseStream, ServerCallContext context)
        {
            var userName = string.Empty;
            var chatRoomId = string.Empty;
            
            while (true)
             {
                //Read a message from the client.
                var clientMessage = await _chatRoomService.ReadMessageWithTimeoutAsync(requestStream, Timeout.InfiniteTimeSpan);

                switch (clientMessage.ContentCase)
                {
                    case ClientMessage.ContentOneofCase.Login:

                        var loginMessage = clientMessage.Login;
                        //get username and chatRoom Id from clientMessage.
                        chatRoomId = loginMessage.ChatRoomId;
                        userName = loginMessage.UserName;

                        if (string.IsNullOrEmpty(userName) || string.IsNullOrEmpty(chatRoomId))
                        {
                            //Send a login Failure message.
                            var failureMessage = new ServerMessage
                            {
                                LoginFailure = new ServerMessageLoginFailure { Reason = "Invalid username" }
                            };

                            await responseStream.WriteAsync(failureMessage);

                            return;
                        }

                        //Send login succes message to client
                        var successMessage = new ServerMessage { LoginSuccess = new ServerMessageLoginSuccess() };
                        await responseStream.WriteAsync(successMessage);

                        //Add client to chat room.
                        await _chatRoomService.AddClientToChatRoom(chatRoomId, new ChatClient
                        {
                            StreamWriter = responseStream,
                            UserName = userName
                        });

                        break;

                    case ClientMessage.ContentOneofCase.Chat:

                        var chatMessage = clientMessage.Chat;

                        if (userName is not null && chatRoomId is not null)
                        {
                            //broad cast the message to the room
                            await _chatRoomService.BroadcastMessageToChatRoom(chatRoomId, userName, chatMessage.Text);
                        }

                        break;
                }
            }
        }
    }
}