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C# "No connection could be made because the target machine actively refused it"

I'm writing a server/client application. my server works great on local ip addresses and i am able to test all of its features using 127.0.0.1 as ip address and communicate with my server.
Today i used my public ip address as ip address in my server application and i configured my port forwarding and checks it with common tools on network and everyone says my port is open an actually i get port checker site packets on my server that shows everything works fine.
but when i want to connect from my client application that it is written in c#(also my server is in c#) i get exception in Socket.Connect function that code is below "No connection could be made because the target machine actively refused it" :
clientSocket = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
Console.WriteLine("Connectiong to server");
clientSocket.Connect("151.243.130.245", 1892);
and here is my listen method on my server :
serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
for (int i = 0; i < MAX_CLIENTS; ++i)
{
clients[i] = new Client();
}
serverSocket.Bind(new IPEndPoint(IPAddress.Any, 1892));
serverSocket.Listen(MAX_CLIENTS);
serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), null);
i have to mention that i tested port checker sites from my friend home and it did send a packet to my server.
also i have a wireless usb adaptor connected to my computer and i am connected with it to my mode.
i did search all the internet and everyone said that in this error common issues are you are not listening on that port or you are blocked by a firewall program but i have to say that i did both of them,it means i used -netstat -anb and it shows i am listening on port 1892 and also i configure firewall to let any connection goes through it but still no luck :(
any helps will greatly be appreciated.

How to emulate PuTTY raw connection in C#?

Please forgive my ignorance, but I believe I just need to be pointed in the right direction...
I have a device that communicates with my PC via Ethernet. I open PuTTY, put in the IP, port, and select a raw connection type. After successful connection, I can then type an "R" to receive one sample from this device. This works without issue.
I've tried many examples I've found for achieving this exact thing in C# (MSDN socket examples, blog examples) and everything so far has fallen short.
private static void StartClient()
{
// Connect to a remote device.
try
{
IPAddress ipAddress = IPAddress.Parse("192.168.0.4");
IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);
// Create a TCP/IP socket.
Socket client = new Socket(AddressFamily.InterNetwork,
SocketType.Raw, ProtocolType.Raw);
// Connect to the remote endpoint.
client.BeginConnect(remoteEP,
new AsyncCallback(ConnectCallback), client);
connectDone.WaitOne();
var isConnected = client.Connected;
// Send test data to the remote device.
Send(client, "S");
sendDone.WaitOne();
I modified this example (from MSDN: https://msdn.microsoft.com/en-us/library/fx6588te(v=vs.110).aspx) to include the IP and port I'm using and I attempted to change the SocketType and ProtocolType to raw. The device's datasheet does say that it ships with TCP as it's default.
I cannot establish a connection to this device at all, let alone write to and read from it.
Any advice would be greatly appreciated.

Allow client app to automatically connect to server app on same network

I've created two apps (A client and a server) which can communicate with each other as long as I input the local IP address of the machine the server app is running on into the client app (in code).
I would like the client app to automatically discover the local IP address of the machine running the server app and connect to it, so they can be run on any network without the need to enter the IP in code.
Both of these apps with be running on the same network (ie. Over WiFi, not the Internet)
Here is what I have so far in my client app:
// COMMUNICATE WITH SERVER
private TcpClient client = new TcpClient();
private IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("192.168.2.35"), 8888);
public Console()
{
InitializeComponent();
client.Connect(serverEndPoint);
}
private void SendMessage(string msg)
{
NetworkStream clientStream = client.GetStream();
ASCIIEncoding encoder = new ASCIIEncoding();
byte[] buffer = encoder.GetBytes(msg);
clientStream.Write(buffer, 0, buffer.Length);
clientStream.Flush();
}
In this example I can only connect to a server running on "192.168.2.35", I would like it to be able to find the server running on port 8888 on any machine on the network.
Alternatively, if this isn't possible I would like the server to broadcast its IP as a message (of some sort) and have the client receive this message and verify it is the server and connect to it.
I think my second example is the proper way to do this, but I can't seem to wrap my head around how to get it working (I'm fairly new to C#), and any other examples I've found I can't seem to get to work with my applications.
Here is my server code if it helps answer my question:
private void Server()
{
this.tcpListener = new TcpListener(IPAddress.Any, 8888);
this.listenThread = new Thread(new ThreadStart(ListenForClients));
this.listenThread.Start();
}
private void ListenForClients()
{
this.tcpListener.Start();
while (true)
{
TcpClient client = this.tcpListener.AcceptTcpClient();
connectedClients++;
lblNumberOfConnections.Text = connectedClients.ToString();
Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));
clientThread.Start(client);
}
Thanks
EDIT: I've tried adding THIS to my project, but being so new I'm unsure how to implement it properly, and it didn't get me anywhere.
2nd EDIT: I've tried implementing a UDP broadcast a few times now, with no luck on any attempt yet. My latest attempt was at implementing THIS (minus the chat parts). I just can't seem to get a UDP broadcast working at all with my project, as it seems to be way over my head at my current skill level. Unfortunately, having my client automatically connect to the server is 100% necessary for my project to function...
My other problem, which is maybe best to start a separate question for, but somewhat correlates to this issue is: My client GUI consists of a panel that switches between multiple custom classes, each containing different buttons, etc. (works similar to tab pages) that communicate to the server I'm trying to connect to. Once I get the UDP broadcast figured out, will I need to code that into every class separately? or is there a way of having all classes running in my panel connect to the same server?

A simple, but possibly costly(in terms of network traffic) solution would be for your server application to broadcast over UDP it's application and connection info. Your client could listen for all broadcast packets that have your servers custom header. Assuming a connection is made you could stop the broadcast. The downside is you would have to be broadcasting constantly if a client is not connected and this can clog your network if there aren't limits placed on the broadcast speed.
EDIT: Here is a boiled down explanation generated from the MSDN article https://msdn.microsoft.com/en-us/library/tst0kwb1(v=vs.110).aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-1
EDIT #2: I've expanded on this answer on my blog, as well as provided downloadable example projects. the article can be found at http://martialdeveloper.com/wordpress/?p=21
1. Find your network's broadcast IP
A special “Broadcast Address” must be used when using UDP for the purpose of sending a datagram to all machines connected to a given network. For example, the typical home network host/gateway of 192.168.0.1 has a broadcast address of 192.168.0.255. If your network differs from this you can use an IPv4 broadcast address calculator like the one found here http://jodies.de/ipcalc
Or read the introductory section on MSDN describing the broadcast address. https://msdn.microsoft.com/en-us/library/tst0kwb1(v=vs.110).aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-1
2. Select a listening/broadcast port
Any port that is free on your client & server is fine. The MSDN example uses 11000. This port number is used in your broadcaster, and listener.
3. Code for the Listener
Note to the reader. All error handling has been omitted for clarity of the example.
int listenPort = 11000;
bool done = false;
UdpClient listener = new UdpClient(listenPort);
IPEndPoint groupEP = new IPEndPoint(IPAddress.Any,listenPort);
while (!done) // This loop listens for your broadcast packets
{
Console.WriteLine("Waiting for broadcast");
byte[] bytes = listener.Receive( ref groupEP);
Console.WriteLine("Received broadcast from {0} :\n {1}\n",
groupEP.ToString(),
Encoding.ASCII.GetString(bytes,0,bytes.Length));
}
listener.Close();
Note: The third parameter to Console.WriteLine, "Encoding.ASCII..." represents the string value sent over UDP in the datagram packet. This contains the desired negotiation information for a discovery situation, such as the IP address of the client or server you wish to connect to.
4. Code for the Broadcaster
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
ProtocolType.Udp);
IPAddress broadcast = IPAddress.Parse("This string should be the broadcast IP address"); //NOTE: Broadcast IP goes here!!
byte[] sendbuf = Encoding.ASCII.GetBytes("This is the message string to be broadcast"); //Your message to the client/server goes here, I.E. an
// app/client name or ID and an IP to connect with over TCP
IPEndPoint ep = new IPEndPoint(broadcast, 11000);
s.SendTo(sendbuf, ep);
Console.WriteLine("Message sent to the broadcast address");
NOTE: This is a very simple example. The broadcaster may need to rebroadcast for a period of time to make sure the Listener receives it. Even after the UDP datagram is sent/received there will need to be some negotiation to ensure the TCP connection is made properly.

Finding open TCP port in a network

I'm trying to build a netowrk app. I have succesfully made a server that sends and receives packages. So far, testing has been done on one computer pointing to 127.0.0.1 (No place like home). Now I want to switch to the network. How can I find computers on a LAN network that are listening to my specific port?

The service will need to listen for broadcast messages on a known port (if you want to be really well behaved you can register the program and port number with the IANA), when it hears a broadcast message it replies to the sender the server's IP and what port the service is listening for incoming connections on.
Here is a simple example from the link above, this just prints to the console who connected and on what port, but you can use this information to establish a TCP or UDP connection between the two endpoints.
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
class RecvBroadcst
{
public static void Main()
{
Socket sock = new Socket(AddressFamily.InterNetwork,
SocketType.Dgram, ProtocolType.Udp);
IPEndPoint iep = new IPEndPoint(IPAddress.Any, 9050);
sock.Bind(iep);
EndPoint ep = (EndPoint)iep;
Console.WriteLine("Ready to receive…");
byte[] data = new byte[1024];
int recv = sock.ReceiveFrom(data, ref ep);
string stringData = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine("received: {0} from: {1}",
stringData, ep.ToString());
data = new byte[1024];
recv = sock.ReceiveFrom(data, ref ep);
stringData = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine("received: {0} from: {1}",
stringData, ep.ToString());
sock.Close();
}
}
As a psudo example here is the sequence of events on how I would do it.
For this example lets say we have a network with a IP of 192.168.1.0 and a subnet of 255.255.255.0. We have two servers, Server1 at 192.168.1.2 with the service listening on port 1234, and Server2 at 192.168.1.3 with a port of 4567 for the service. Both are listing on port 3000 for broadcast messages. The client connecting will be at the IP 192.168.1.4
Client chooses a random port in the dynamic port range(49152-65535) and binds to it on UDP (port 50123 for this example) and listens.
The client broadcasts to the broadcast address and the known port for his local subnet (192.168.1.255:3000) using the same port to send as he is listening on. He sends some kind of payload so the servers only send back to your clients, instead of someone else who happened to use the same port as you. (lets say it sends the string Send me your info for XYZ app!)
Server1 receives the broadcast. Checks that the message is Send me your info for XYZ app! and sends the UDP message Name:Server1 IP:192.168.1.2 Port:1234 back to the senders source port and IP combination (192.168.1.4:50123)
Server2 receives the broadcast also. Checks that the message is Send me your info for XYZ app! and sends the UDP message Name:Server2 IP:192.168.1.3 Port:4567 message back to the senders source port and IP combination (192.168.1.4:50123)
The client receives two UDP messages on the same port he sent the message on. He parses the replies and displays to the user the two servers available to connect to.

TCP socket error 10061

I have created a windows service socket programme to lisen on specific port and accept the client request. It works fine.
protected override void OnStart(string[] args)
{
//Lisetns only on port 8030
IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Any, 8030);
//Defines the kind of socket we want :TCP
Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
//Bind the socket to the local end point(associate the socket to localendpoint)
serverSocket.Bind(ipEndPoint);
//listen for incoming connection attempt
// Start listening, only allow 10 connection to queue at the same time
serverSocket.Listen(10);
Socket handler = serverSocket.Accept();
}
But I need the service programme to listen on multiple port and accept the client request on any available port.
So I enhanced the application to bind to port 0(zero), so that it can accept the request on any available port.
But then I got the error 10061
No connection could be made because the target machine actively refused it.
I am unable to know whats the reason of getting this error.
Can anybody please suggest the way to enhance the code to accept the request on any port.
But the client need to send request to connect to specific port. e.g client1 should connect to port 8030, client2 should connect to port 8031.

So I enhanced the application to bind to port 0(zero), so that it can accept the request on any available port.
Wrong. 0 means that the OS should assign a port. A server can only listen at one port at a time. The listen socket just accepts new connections.
The new connection will have the same local port, but the combination of Source (ip/port) and destination (ip/port) in the IP header is used to identify the connection. That's why the same listen socket can accept multiple clients.
UDP got support for broadcasts if that's what you are looking for.
Update:
A very simplified example
Socket client1 = serverSocket.Accept(); // blocks until one connects
Socket client2 = serverSocket.Accept(); // same here
var buffer = Encoding.ASCII.GetBytes("HEllo world!");
client1.Send(buffer, 0, buffer.Count); //sending to client 1
client2.Send(buffer, 0, buffer.Count); //sending to client 2
Simply keep calling Accept for each client you want to accept. I usually use the asynchronous methods (Begin/EndXXX) to avoid blocking.