Why SignalR cannot connect across machines?

Question

I have a C# .NET Framework client and server, and I use SignalR to make them communicate. When I deploy the client and server in the same machine, they can make connection well, but if I move the client to another machine, it can never connect to the server and it return the error

A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.224.10.10:12345

I have already added the port 12345 into Inbound Rule with Local port = 12345, Protocol type = TCP.

Client side code

//Create a connection for the SignalR server
_signalRConnection = new  HubConnection("http://10.224.10.10:12345/signalr/SimpleHub/"); 
  
//Get a proxy object that will be used to interact with the specific hub on the server 
//There may be many hubs hosted on the server, so provide the type name for the hub 
_hubProxy = _signalRConnection.CreateHubProxy("SimpleHub");

Server side code

using Microsoft.Owin.Hosting; 
using Microsoft.AspNet.SignalR; 
using System.ComponentModel;  
namespace WinFormsServer 
{     
    public partial class FrmServer : Form     
    {         
        private IDisposable _signalR;         
        private void btnStartServer_Click(object sender, EventArgs e)         
        {             
            try             
            {                 
                //Start SignalR server with the give URL address                         
                //Final server address will be "URL/signalr"                     
                //Startup.Configuration is called automatically                 
                _signalR = WebApp.Start<Startup>("http://*:12345/");                 
                writeToLog($"Server started at:{txtUrl.Text}");             
            }             
            catch (Exception ex)             
            {                 
                MessageBox.Show(ex.Message, "Error",         
                MessageBoxButtons.OK, MessageBoxIcon.Error);             
            }         
        }     
    } 
}

using Owin; 
using Microsoft.Owin.Cors;  
namespace WinFormsServer 
{     
    class Startup     
    {         
    public void Configuration(IAppBuilder app)         
    {             
        //CORS need to be enabled for calling SignalR service
        app.UseCors(CorsOptions.AllowAll);             
        //Find and reigster SignalR hubs
        app.MapSignalR();         
    }     
    } 
}