What is the best way for a client app to find a server on a local network in C#?

Question

The client connects to the server using GenuineChannels (we are considering switching to DotNetRemoting). What I mean by find is obtain the IP and port number of a server to connect to.

It seems like a brute-force approach would be try every IP on the network try the active ports (not even sure if that's possible) but there must be a better way.

Answer 1

Consider broadcasting a specific UDP packet. When the server or servers see the broadcasted UDP packet they send a reply. The client can collect the replies from all the servers and start connecting to them or based on an election algorithm.

See example for client (untested code):

---

using System.Net;
using System.Net.Sockets;

[STAThread]
static void Main(string[] args)
{
    Socket socket = new Socket(AddressFamily.InterNetwork,
    SocketType.Dgram, ProtocolType.Udp);
    socket.Bind(new IPEndPoint(IPAddress.Any, 8002));
    socket.Connect(new IPEndPoint(IPAddress.Broadcast, 8001));
    socket.Send(System.Text.ASCIIEncoding.ASCII.GetBytes("hello"));

    int availableBytes = socket.Available;
    if (availableBytes > 0)
    {
        byte[] buffer = new byte[availableBytes];
        socket.Receive(buffer, 0, availableBytes, SocketFlags.None);
        // buffer has the information on how to connect to the server
    }
}