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Multible programs/instances using the same UDP Port in C#

I am struggling with a bit of network magic and hoped someone would be able to explain me what is happening.
I am trying to reuse udp ports. So if I have multible programs listening on the same udp port i want both of the applications to receive the data send by a different device.
Using the following code I'am able to achive just that:
IPEndPoint localEndoint = new IPEndPoint(IPAddress.Any, 67); //the local endpoint used to listen to port 67
//Create a new UDP Client and bind it to port 67
DhcpSniffer = new UdpClient();
DhcpSniffer.ExclusiveAddressUse = false; //Allow multible clients to connect to the same socket
DhcpSniffer.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true); // Connect even if socket/port is in use
DhcpSniffer.Client.Bind(localEndoint);
DhcpSniffer.Client.ReceiveTimeout = Timeout;
//receive on port 67
dhcpPacket = DhcpSniffer.Receive(ref localEndoint);
Both of my programs can listen to DHCP messages in the network and don't block each other.
Now i want to do the same thing with port 15120 where a RTP video stream is streamed to. However this does not work. I am using the same code but with no success only one application at a time can receive the stream, the other will run in a timeout.
IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, port);
//Create a new UDP Client and bind it to port 15120
udpReceiver = new UdpClient();
udpReceiver.ExclusiveAddressUse = false; //this is an attempt to receive the stream on mutlible instances...this works for DHCP but not for RTP for some reason....
udpReceiver.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true); // Connect even if socket/port is in use
udpReceiver.Client.ReceiveTimeout = timeout; //set the sockete timeout
udpReceiver.Client.Bind(RemoteIpEndPoint); //bind to the port from any IP
//receive packets on port 15120
Byte[] receiveBytes = udpReceiver.Receive(ref RemoteIpEndPoint);
I hope somebody is able to shine a light on my confusion
Update:
I found out it works with DHCP because it is send to the broadcast IP (255.255.255.255). Now I need to find out how i can change the Socket behaviour to treat my RTP stream as if it was broadcasted so i can see it in two application at the same time. (Yes I could configure my stream-source to broadcast, but this is not the goal of this).
The goal is to reconfigure the Socket to behave as explained. Not to save the stream on a harddrive or redirect it using the local host.

First, its not possible to have multiple programs listen on the same port (As far as I know it's a big security conflict)
What you can do tough, is use a NetworkManager that listen on you port (Lets call it port 8080) who will then redirect the information to you apps ports (App1 could use port 8081 and App2 use port 8082). Either you write your own, using Flask to listen on 8080 and then rerouting the package to localhost:8081 and localhost:8082 could be a simple and fast solution.
Doing this would help you secure the network and you can redirect to as many ports as you need, pretty much like a docker swarm would balance the incoming network to its cluster.

It is not possible with multible programs to access the data from a unicast UDP package, it works only with multicast, there is no "easy" way around this by reconfiguring the UdpClient

Multicast Socket Not Receiving After Disabling/Enabling Network Connection

I'm using Socket with following configuration to receive multicast packets and the code is working properly.
socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
socket.Bind(bindPoint);
socket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.AddMembership, new MulticastOption(multicastAddress, IPAddress.Any));
socket.ReceiveTimeout = 1000;
But after disabling the network connection from Control Panel and enabling, the socket cannot receive the multicast data. I can see the packets with Wireshark. I tried closing the socket, resetting he socket but restarting is the only solution I came up with. The application will be used in an environment where the user typically remove the ethernet cable and plug another one.
Initially I was using UdpClient but the same problem persists on that too. The operating system is Windows 7 and I use .NET 4.5.2.

After disabling a network connection, Windows automatically uses another connection if you have one (virtual host etc.). After enabling the previous connection, the application doesn't use the correct connection since there were no interface selection made. Disabling other connections or specifying the interface solves the problem.

Server Client Application with .NET and Xamarin

I searched around the internet a lot of hours but I couldn't find anything that matches my case.
I simply want to implement a Server/Client App with TCP or UDP where my Android App (Xamarin) acts as a server and my .NET application as Client. Since I have not much experience with app development and no experience with Xamarin, I was looking for an example. All I found was this:
http://www.codeproject.com/Articles/340714/Android-How-to-communicate-with-NET-application-vi
First of all this is the opposite way (Server on .NET and Client as App) and additionaly it is for Android Studio so it's hard for me to translate these things into Xamarin without errors.
Please can someone help and give me an example how to realize my issue?
Thank you!

On Xamarin.Android you can use all of the regular .Net socket classes:
Namespaces:
using System.Net;
using System.Net.Sockets;
Example:
IPHostEntry ipHostInfo = Dns.GetHostEntry (Dns.GetHostName ());
IPAddress ipAddress = ipHostInfo.AddressList [0];
IPEndPoint localEndPoint = new IPEndPoint (ipAddress, 11000);
System.Diagnostics.Debug.WriteLine(ipAddress.ToString());
// Create a TCP/IP socket.
Socket listener = new Socket (AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
AndroidManifest.xml Required Permissions are:
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
The MSDN-based Asynchronous Server Socket example works as a cut/paste example with no changes.
i.e.
Using the MSDN code, you can call the static method, AsynchronousSocketListener.StartListening, in a thread to start listening on port 11000 defined in the AsynchronousSocketListener class.
new Thread (new ThreadStart (delegate {
AsynchronousSocketListener.StartListening();
})).Start ();
Once it is running on your device/emulator, you can telnet into your Android TCP socket server:
>telnet 10.71.34.100 11000
Trying 10.71.34.100...
Connected to 10.71.34.100.
Escape character is '^]'.
Once connected, type in This is a test<EOF> and the Android will echo it back:
This is a test<EOF>

You do this like in normal .net, except you have to ask permissions to use sockets.
There are tons of simple example of creating a listening tcp connection in c#.
The problem you will have is to know the IP address of your server (in the phone) as it will likely change often when the user is moving.

No connection could be made because the target machine actively refused it [not similar to others]

I'm trying to learn Socket Programming, and I encountered this error while connecting to my server application.
Here's my declaration of the TcpListener in the server application:
TcpListener listener = new TcpListener(IPAddress.Loopback, 5152);
and here's my declaration of the TcpClient in my client application:
TcpClient client = new TcpClient(Dns.GetHostEntry(IPAddress.Loopback).HostName, 5152);
I have read several questions like this, and I always get the same answer: Either the server application isn't listening to the port or not running at all. But I've double-checked the Resource Monitor and cmd using netstat to see if the service is listening to the port, and it is. I've also included the service in the Firewall exceptions, so I'm not sure why I keep getting this error while trying to connect to the server app.
Any ideas?

Dns.GetHostEntry(IPAddress.Loopback).HostName returns the host name of your machine. When you pass a host name to TcpClient, it will resolve it to one or more IP addresses using Dns.GetHostAddresses(hostName). This includes the public and link-local IP addresses of your machine (e.g., 192.168.15.4), but not the loopback address (127.0.0.1).
So your client is trying to connect to any of the non-loopback addresses of your machine, while your server is listening only on the loopback address. Thus, no connection can be established.
Solution: Connect to the same end point your server is listening on.
IPEndPoint endPoint = new IPEndPoint(IPAddress.Loopback, 5152);
TcpListener listener = new TcpListener(endPoint);
TcpClient client = new TcpClient();
client.Connect(endPoint);

I can't connect to my server over the internet

I can run the server on my local machine and connect to it on the same machine, but when I try to connect to it from a different computer over the internet, there is not sign of activity on my server, nor a response from the server on the computer I'm testing it on. I've tried both XP and Vista, turn off firewalls, opened ports, ran as admin; nothing is working. :(
Here is my code that I'm using to accept an incoming connection:
int port = 3326;
Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
try
{
TcpListener listener = new TcpListener(new IPEndPoint(IPAddress.Any, port));
listener.Start();
Console.WriteLine("Server established\nListening on Port: {0}\n", port);
while (true)
{
socket = listener.AcceptSocket();
socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendTimeout, outime);
socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);
socket.DontFragment = true;
NewConnection pxy = new NewConnection(socket);
Thread client = new Thread(new ThreadStart(pxy.Start));
client.IsBackground = true;
client.Start();
}
}

I think that the problem is in your router, not your computer. When packets come from the Internet, it should be routed to an specific server. You have to configure your router to redirect the traffic on port 3326 to your server.

You've probably got something blocking the connection higher up. Try connecting from another host on the LAN. If you can do that, then the OS itself isn't firewalling the connection.
If either you or your ISP run a NAT router, then your machine probably doesn't have a publicly accessible address, in which case it's impossible to connect directly to it.
If there is no NAT router, something may still be blocking the connection upstream.

I am serious: Many ISPs actively work to stop you from using your home connection as a web server. You might want to call them before you invest too much time.

If you are trying to host at home, your ISP may be restricting you.