如何使用SignalR将消息发送到特定客户端

Question

If I have multiple clients connected to hub, how would I get the details of all the connected clients from client side(.aspx) using JavaScript.
In the SendChatMessage() method, I have to pass "who" parameter from the client side(.aspx) but how would I get to know the connection Id or username of the a particular clients among so many connected clients.

public class Chathub : Hub
{
    private readonly static ConnectionMapping<string> _connections =
        new ConnectionMapping<string>();

    public void SendChatMessage(string who, string message)
    {
        string name = Context.User.Identity.Name;

        foreach (var connectionId in _connections.GetConnections(who))
        {
            Clients.Client(connectionId).addChatMessage(name + ": "message);
        }
    }

    public override Task OnConnected()
    {
        string name = Context.User.Identity.Name;
        _connections.Add(name, Context.ConnectionId);
        return base.OnConnected();
    }


 public class ConnectionMapping<T>
 {
    private readonly Dictionary<T, HashSet<string>> _connections =
        new Dictionary<T, HashSet<string>>();

    public int Count
    {
        get
        {
            return _connections.Count;
        }
    }

    public void Add(T key, string connectionId)
    {
        lock (_connections)
        {
            HashSet<string> connections;
            if (!_connections.TryGetValue(key, out connections))
            {
                connections = new HashSet<string>();
                _connections.Add(key, connections);
            }

            lock (connections)
            {
                connections.Add(connectionId);
            }
        }
    }

    public IEnumerable<string> GetConnections(T key)
    {
        HashSet<string> connections;
        if (_connections.TryGetValue(key, out connections))
        {
            return connections;
        }

        return Enumerable.Empty<string>();
    }

Answer 1

While sending message to specific client, you have to call chathub.server.sendMessage() from client

public void SendPrivateMessage(string toUserId, string message)
        {

            string fromUserId = Context.ConnectionId;

            var toUser = ConnectedUsers.FirstOrDefault(x => x.ConnectionId == toUserId) ;
            var fromUser = ConnectedUsers.FirstOrDefault(x => x.ConnectionId == fromUserId);

            if (toUser != null && fromUser!=null)
            {
                // send to 
                Clients.Client(toUserId).sendMessage(fromUserId, fromUser.UserName, message); 

                // send to caller user as well to update caller chat
                Clients.Caller.sendMessage(toUserId, fromUser.UserName, message); 
            }

        }

Clients.Caller.sendMessage(toUserId, fromUser.UserName, message); note that this is client method, to update the chat.

Then in client side, call chathub.server.sendMessage(id,msg) where you can pass id of that specific user To get id you have to use jQuery, eg first you have to save id of each client in client side lets say

<a id='userid' class="username"></a> 

and on click event you can get the id of that user like

    $("a").on('click',function(){

    var touser = $(this).attr('id'))
    }

chathub.server.sendMeassage(touser,msg);

This may not the complete solution, but you have to do like this.

There's good post here which shows the idea.