Introduction
This solution explains a socket approach to sending a message (broadcast message) to clients in the same VLAN (Virtual Lan). If broadcasting is needed for the whole LAN (over all VLANs) in the same local area network then you have to use Remoting instead of Sockets.
How To Send Message to Connected LAN Clients Using Broadcasting
The application consists of two programs "Clfrm" and "SERVfrm." Clfrm exists on all LAN computers and SERVfrm exists on the server.
When the time is 12:00 AM the SERVfrm will send a broadCast message to all connected clients (Clfrm). The Clfrm will receive the message and run an alert form to notify the user.
Using the Code
I use the following namespace to do my job:
System.Net
System.Net.Sockets
The time was an important factor, as was having no delay when sending/receiving a message from the server to all clients. So, I used sockets instead Of remoting (remoting may cause a simple delay).
The Server Code
private void timer1_Tick(object sender, System.EventArgs e)
{
label1.Text = System.DateTime.Now.ToLongTimeString();
The timer here is to get the server time.
if(System.DateTime.Now.Hour == 11 && System.DateTime.Now.Minute==59 &&
System.DateTime.Now.Second==59)
Check if the time is 11:59:59.
{
Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
ProtocolType.Udp);
IPEndPoint iep1 = new IPEndPoint(IPAddress.Broadcast, 9050);
IPEndPoint iep2 = new IPEndPoint(IPAddress.Parse("192.168.100.255"),9050);
byte[] data = Encoding.ASCII.GetBytes("12");
Set Socket Options ---> SocketOptionLevel
Member name Description
IP Socket options apply only to IP sockets.
IPv6 Socket options apply only to IPv6 sockets.
Socket Socket options apply to all sockets.
Tcp Socket options apply only to TCP sockets.
Udp Socket options apply only to UDP sockets.
*/
sock.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.Broadcast, 1);
sock.SendTo(data, iep1);
sock.SendTo(data, iep2);
sock.Close();
}
Note
In the first run of the client application the firewall will show the below message. When The Clfrm runs on the client machine it will not appear in the desktop or task manager Application tab.
I put ShowInaskbar = false
in 'Clfrm' which will hide the 'Clfrm' from the Task Manager Application Tab (it will appear in the process tab), and made Opacity = 2
Press unlock to allow the client to use 9050 port to receive messages from the server.
The Client Code
public string TI ="0";
string stringData ;
This timer will check the value of stringData
private void timer1_Tick(object sender, System.EventArgs e)
{
Socket sock = new Socket(AddressFamily.InterNetwork,SocketType.Dgram,
ProtocolType.Udp);
IPEndPoint iep = new IPEndPoint(IPAddress.Any, 9050);
sock.Bind(iep);
byte[] data = new byte[1024];
int recv = sock.ReceiveFrom(data, ref ep);
stringData = Encoding.ASCII.GetString(data, 0, recv);
TI=stringData;
sock.Close();
}
private void timer2_Tick(object sender, System.EventArgs e)
{
if(TI == "12")
{
timer2.Interval = 3000;
TI = "0";
stringData = "0";
Process.Start(Application.StartupPath+"\\ALER.exe");
}
else
{
timer2.Interval =400;
}
}
The sock.Close();
will close the port 9050 for future use.
Why Using Sockets instead of Remoting
- If you need bidirectional communication and if the data is a small fragment use sockets
- If you want the best performance
- When Client is waiting for notifications/events from server
- Remoting is a higher layer on Sockets. When both client and server is under your control you can use Remoting
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