UdpClient.JoinMulticastGroup Method

public void JoinMulticastGroup(int multicastAddress)

public void JoinMulticastGroup(IPAddress multicastAddress)

public void JoinMulticastGroup(int multicastAddress, int timeToLive)

public void JoinMulticastGroup(IPAddress multicastAddress, int timeToLive)

Initializes a new instance of the UdpClient class and joins the specified multicast group.

Parameters

multicastAddress: An IPAddress representing the multicast group to join.
OR An integer that specifies the IP address of the multicast group to join.
timeToLive: The maximum number of network hops the multicast datagram can take before being discarded. A value of 1 means that datagrams can only be delivered to hosts on the local network.

Returns

void: This method does not return a value.

Exceptions

ArgumentNullException: multicastAddress is null.
SocketException: An error occurred while accessing the socket.
ObjectDisposedException: The UdpClient has been closed.

Remarks

Multicast allows a single datagram to be sent to multiple destinations simultaneously. You can use the JoinMulticastGroup method to subscribe to a multicast group.

The timeToLive parameter controls the scope of the multicast. A timeToLive of 1 restricts multicast traffic to the local network segment. Higher values allow traffic to propagate across routers.

To leave a multicast group, use the LeaveMulticastGroup method.

Note: Multicast group addresses are in the range of 224.0.0.0 through 239.255.255.255.

Examples

The following code example demonstrates how to join a multicast group.


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

public class MulticastExample
{
    public static void Main(string[] args)
    {
        try
        {
            // Define the multicast group address and port
            IPAddress multicastAddr = IPAddress.Parse("239.255.0.1");
            int port = 12345;

            // Create a UdpClient and join the multicast group
            using (UdpClient udpClient = new UdpClient(port))
            {
                udpClient.JoinMulticastGroup(multicastAddr);
                Console.WriteLine($"Joined multicast group: {multicastAddr}");

                // Here you would typically start listening for multicast datagrams
                // or send datagrams to the group.

                // For demonstration, we'll wait a bit and then leave.
                Console.WriteLine("Waiting for 10 seconds...");
                System.Threading.Thread.Sleep(10000);

                udpClient.LeaveMulticastGroup(multicastAddr);
                Console.WriteLine($"Left multicast group: {multicastAddr}");
            }
        }
        catch (SocketException e)
        {
            Console.WriteLine($"SocketException: {e.Message}");
        }
        catch (Exception e)
        {
            Console.WriteLine($"General exception: {e.Message}");
        }
    }
}