Reply back to exactly same client who connected and called with SignalR - asp.net-mvc

Question

I am having a two tier application, with one being Windows Form application and other being Web Application with MVC.
Desktop Application has a SignalR Hub area which manages all client connected to it from Web App.
Hub Class
public delegate void ClientConnectionEventHandler(string clientId);
public delegate void ClientNameChangedEventHandler(string clientId, string newName);
public delegate void ClientInitializeEventHandler(string clientId);
public class StockTickerHub:Hub
{
static ConcurrentDictionary<string, string> _users = new ConcurrentDictionary<string, string>();
public static event ClientConnectionEventHandler ClientConnected;
public static event ClientConnectionEventHandler ClientDisconnected;
public static event ClientNameChangedEventHandler ClientNameChanged;
public static event ClientInitializeEventHandler ClientInitialized;
//Called when a client is connected
public override Task OnConnected()
{
_users.TryAdd(Context.ConnectionId, Context.ConnectionId);
ClientConnected?.Invoke(Context.ConnectionId);
return base.OnConnected();
}
public override Task OnDisconnected(bool stopCalled)
{
string username;
_users.TryRemove(Context.ConnectionId, out username);
ClientDisconnected?.Invoke(Context.ConnectionId);
return base.OnDisconnected(stopCalled);
}
public void SetUserName(string userName)
{
_users[Context.ConnectionId] = userName;
ClientNameChanged?.Invoke(Context.ConnectionId, userName);
}
public void InitializeGrid()
{
ClientInitialized?.Invoke(Context.ConnectionId);
}
}
When web client connects to Desktop App, it's being added and connected.
Inherited Hub Class
public class ClientGateway
{
private BindingList<ClientItem> _clients = new BindingList<ClientItem>();
frmMasterTicker frm;
public ClientGateway()
{
//Register to hub events
StockTickerHub.ClientConnected += StockTickerHub_ClientConnected;
StockTickerHub.ClientNameChanged += StockTickerHub_ClientNameChanged;
StockTickerHub.ClientDisconnected += StockTickerHub_ClientDisconnected;
StockTickerHub.ClientInitialized += StockTickerHub_ClientInitialized;
}
private void StockTickerHub_ClientInitialized(string clientId)
{
InitializeGrid(clientId);
}
private void StockTickerHub_ClientDisconnected(string clientId)
{
var client = _clients.FirstOrDefault(x => x.Id == clientId);
if (client != null)
{
_clients.Remove(client);
}
}
private void StockTickerHub_ClientNameChanged(string clientId, string newName)
{
//Update client's name if it's available
var client = _clients.FirstOrDefault(x => x.Id == clientId);
if (client != null)
{
client.Name = newName;
SetOperationLogMessage.AddLogMessage(this.ToString(), "", $"Client name changed. Id:{clientId}, Name:{newName}");
SendTestMessage();
}
}
private void StockTickerHub_ClientConnected(string clientId)
{
//Add client to the list
_clients.Add(new ClientItem() { Id = clientId, Name = clientId });
SetOperationLogMessage.AddLogMessage("ClientGateway", "StockTickerHub_ClientConnected", $"Client connected:{clientId}");
}
public void SendTestMessage()
{
var hubContext = GlobalHost.ConnectionManager.GetHubContext<StockTickerHub>();
hubContext.Clients.All.addMessage("Ticker Server", "Hello handshake from server.");
}
public void InitializeGrid(string connectionid)
{
if (_clients.Count > 0)
{
frm = (frmMasterTicker)Helper.GetOpenForm("frmMasterTicker");
//string msg = "Hello from server at " + DateTime.Now.ToString();
string msg = JsonConvert.SerializeObject(frm.GetInitializeDataFromGrid());
var hubContext = GlobalHost.ConnectionManager.GetHubContext<StockTickerHub>();
hubContext.Clients.Client(connectionid).initializeGrid(msg);
}
}
public void SendTickerData(object lstStock)
{
if (_clients.Count > 0)
{
//string msg = "Hello from server at " + DateTime.Now.ToString();
string msg = JsonConvert.SerializeObject(lstStock);
var hubContext = GlobalHost.ConnectionManager.GetHubContext<StockTickerHub>();
hubContext.Clients.Client("").getTickerData(msg);
}
}
}
Web Page Code
//Connect to SignalR server and get the proxy
function connect() {
$.connection.hub.url = url;
simpleHubProxy = $.connection.stockTickerHub;
if (simpleHubProxy) {
$.connection.hub.start().done(function () {
writeToLog("Connected...");
simpleHubProxy.server.setUserName("RMSAdmin");
RequestGridInitialData();
})
.fail(function () {
alert("Can't connect");
})
;
simpleHubProxy.client.addMessage = function (name, message) {
writeToLog(name + ":" + message);
}
simpleHubProxy.client.initializeGrid = function (message) {
dtSource = JSON.parse(message);
$("#grid").data("kendoGrid").dataSource.data(dtSource);
}
simpleHubProxy.client.getTickerData = function (message) {
writeToLog(message);
}
$.connection.hub.disconnected(function () {
writeToLog("Server disconnected.");
});
$.connection.hub.reconnecting(function () {
writeToLog("Server reconnecting...");
});
$.connection.hub.reconnected(function () {
writeToLog("Server reconnected...");
});
$.connection.hub.error(function (error) {
console.log('SignalR error: ' + error)
});
}
}
connect();
I can get the connection id from Hub.
Now I have a Windows Form. In which, I want to send data to exactly the same client who connected recently. I have a list of all clients connection with id. But within that, who connected recently and to whom I need to send data from Form, I am unable to do the progress with.
Following is a code try inside a Windows Form, which works, but it sends data to all connected client.
hubContext.Clients.All.getTickerData(JsonConvert.SerializeObject(tmpStock));
I want to send data only to that client who connects recently. How should I do that?

Answer 1

In the piece of code where you are sending the windows form data, you can call:
hubContext.Clients.Caller.getTickerData(JsonConvert.SerializeObject(tmpStock));
The .Caller will send the message to the client that invoked the method.
You can read more about it, in the oficial microsoft documentation, here: https://learn.microsoft.com/en-us/aspnet/signalr/overview/guide-to-the-api/hubs-api-guide-server#selectingclients
Edit: Since you don't have access to the .Caller method outside the hub you need to save the ClientId inside the hub and pass it the the outside class... SO there you will be able to call the caller client by id:
hubContext.Clients.Client(clientId).getTickerData(JsonConvert.SerializeObject(tmpStock));