Develop Reference

Shared resources while using Task.Factory

Here is the code whose responsibility is to connect to the server and get some details.
public class MigrationManager
{
private string referenceServerId;
public void MigrateAnalyzer(string serverid)
{
Gw _Gw = new Gw() // library reference
_Gw.onConnectSucceeded += Handle_OnConnectSucceeded;
_Gw.onConnectFailed += Handle_OnConnectFailed;
ConnectToServer(prxHA, serverid);
}
private void ConnectToServer(string sid)
{
workstationIDForReference = anayzer;
string credentials = GWServiceCredentials("somesecret");
referenceServerId = sid;
_Gw.connectToServer("SSL", "device1-mydomain.net", credentials, referenceServerId);
}
}
This connection operation can end up in two scenarios.
Connection success
Connection failure
These events handled as shown below
private void Handle_OnConnectFailed(int hr)
{
string msg = $"{referenceServerId}";
Console.WriteLine("Connecting to server {0} is failed", msg);
}
private void Handle_OnConnectSucceeded()
{
Console.WriteLine("Connecting to server is success");
}
This works well. Now I am changing it to support multithreading. Because there are multiple requests to connect to the server.
List<string> requestCollection = new List<string>();
requestCollection.Add("I3-1");
requestCollection.Add("I3-2");
requestCollection.Add("I3-3");
var taskList = new List<Task>();
foreach (var serverid in requestCollection )
{
MigrationManager manager = new MigrationManager();
var task = Task.Factory.StartNew(() => manager.MigrateAnalyzer(serverid.ToString()));
}
Task.WaitAll(taskList.ToArray());
I see below Output
Console.WriteLine("Connecting to server I3-1 is failed");
Console.WriteLine("Connecting to server I3-2 is failed");
Console.WriteLine("Connecting to server I3-3 is failed");
Output looks good!
But, I think COM will use shared resources. so how do I use "lock"?

ConnectionRefused in windows 10 IoT

I've created an DHCP server and I've added a TCP server. When I send a message at address IPv4 of the DHCP server, the client answer with: ConnectionRefused.
I've set the property to true
DataSocket = new DatagramSocket();
DataSocket.Control.MulticastOnly = true;
This code running to boot of the app UWP:
private void Start()
{
if (this.StatusButton.Content.ToString().Equals(AVVIA))
{
this.ViewModel.Action = "AVVIO DEL SERVER DHCP IN CORSO...";
RunServer();
this.StatusButton.Content = UPDATE;
Task.Run(async () =>
{
await Task.Delay(DELAY);
Server = new Server();
Server.StartServer();
});
}
... ... ...
private void RunServer()
{
IPAddress iPAddress;
DhcpServer = new ScaemDhcp.DhcpServer();
iPAddress = new IPAddress(new byte[] { 192, 168, 1, 101 });
DhcpServer.Run(iPAddress, DNS, SUB_MASK, SERVER_IDENTIFIER, ROUTER_IP);
}
public void Run(IPAddress iPAddress, string dns, string subnetMask, string serverIdentifier, string routerIP)
{
var server = new Dhcp(iPAddress);
server.ServerName = dns;
server.BroadcastAddress = IPAddress.Broadcast.ToString();
server.OnDataReceived += (sender, dhcpRequest) =>
{
try
{
var type = dhcpRequest.GetMsgType();
var ip = iPAddress;
var replyOptions = new DhcpReplyOptions();
replyOptions.SubnetMask = IPAddress.Parse(subnetMask);
replyOptions.DomainName = server.ServerName;
replyOptions.ServerIdentifier = IPAddress.Parse(serverIdentifier);
replyOptions.RouterIP = IPAddress.Parse(routerIP);
replyOptions.DomainNameServers = new IPAddress[]
{IPAddress.Parse("8.8.8.8"), IPAddress.Parse("8.8.4.4")};
if (type == DhcpMsgType.DHCPDISCOVER)
{
dhcpRequest.SendDHCPReply(DhcpMsgType.DHCPOFFER, ip, replyOptions);
}
if (type == DhcpMsgType.DHCPREQUEST)
{
dhcpRequest.SendDHCPReply(DhcpMsgType.DHCPACK, ip, replyOptions);
}
}
catch (Exception e)
{ }
};
server.Start();
}
... ...
public async void StartServer()
{
try
{
var streamSocketListener = new StreamSocketListener();
streamSocketListener.ConnectionReceived += this.StreamSocketListener_ConnectionReceived;
await streamSocketListener.BindServiceNameAsync(PORT.ToString());
}
catch (Exception ex)
{
... ...

Firstly, you need to check if you have add the capability Private Networks (Client & Server), this capability provides inbound and outbound access to home and work networks through the firewall. Please refer to this document(enter link description here).
And then, you need to check if the port is available, you can add the rules for port 5037 in firewall, please try with following command.
netsh advfirewall firewall add rule name="5037 In" dir=in protocol=TCP localport=5037 action=Allow
netsh advfirewall firewall add rule name="5037 Out" dir=out protocol=TCP localport=5037 action=Allow

From comment by #Michale Xu - MSFT
#Nicolò, I have given a response on MSDN forum about the similar issue.

C# as Websocket server for HTML5 websocket connection

I guess it's already time that I ask others. Is it possible to create a websocket server using C# and server request from HTML5 codes?
I am currently using the System package for websocket. I have a code that I downloaded over the internet and here it is:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace WebSocketChatServer
{
using WebSocketServer;
class ChatServer
{
WebSocketServer wss;
List<User> Users = new List<User>();
string unknownName = "john doe";
public ChatServer()
{
// wss = new WebSocketServer(8181, "http://localhost:8080", "ws://localhost:8181/chat");
wss = new WebSocketServer(8080, "http://localhost:8080", "ws://localhost:8080/dotnet/Chats");
wss.Logger = Console.Out;
wss.LogLevel = ServerLogLevel.Subtle;
wss.ClientConnected += new ClientConnectedEventHandler(OnClientConnected);
wss.Start();
KeepAlive();
}
private void KeepAlive()
{
string r = Console.ReadLine();
while (r != "quit")
{
if(r == "users")
{
Console.WriteLine(Users.Count);
}
r = Console.ReadLine();
}
}
void OnClientConnected(WebSocketConnection sender, EventArgs e)
{
Console.WriteLine("test");
Users.Add(new User() { Connection = sender });
sender.Disconnected += new WebSocketDisconnectedEventHandler(OnClientDisconnected);
sender.DataReceived += new DataReceivedEventHandler(OnClientMessage);
}
void OnClientMessage(WebSocketConnection sender, DataReceivedEventArgs e)
{
Console.WriteLine(sender);
User user = Users.Single(a => a.Connection == sender);
if (e.Data.Contains("/nick"))
{
string[] tmpArray = e.Data.Split(new char[] { ' ' });
if (tmpArray.Length > 1)
{
string myNewName = tmpArray[1];
while (Users.Where(a => a.Name == myNewName).Count() != 0)
{
myNewName += "_";
}
if (user.Name != null)
wss.SendToAll("server: '" + user.Name + "' changed name to '" + myNewName + "'");
else
sender.Send("you are now know as '" + myNewName + "'");
user.Name = myNewName;
}
}
else
{
string name = (user.Name == null) ? unknownName : user.Name;
wss.SendToAllExceptOne(name + ": " + e.Data, sender);
sender.Send("me: " + e.Data);
}
}
void OnClientDisconnected(WebSocketConnection sender, EventArgs e)
{
try
{
User user = Users.Single(a => a.Connection == sender);
string name = (user.Name == null) ? unknownName : user.Name;
wss.SendToAll("server: "+name + " disconnected");
Users.Remove(user);
}
catch (Exception exc)
{
Console.WriteLine("ehm...");
}
}
}
}
And I have this code for client side:
<!HTML>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js">
</script>
<script language="javascript" type="text/javascript">
jQuery(document).ready(function(){
var socket = new WebSocket("ws://localhost:8080");
socket.onopen = function(){
alert("Socket has been opened!");
}
});
</script>
</head>
</HTML>
As I run my C# console app and load the client page, the app tells me that there's someone who connected in the port it is listening to. But on my client side, as I look in firebug's console, it gives me the beginner's classic error:
Firefox can't establish a connection to the server at ws://localhost:8080/
What I would like to achieve is establish first a successful websocket connection and push value to my client coming from my server.
I have considered Alchemy but the version I have is Visual Studio express 2010, the free version, and it says that "solution folders are not supported in this version of application".
Any help will be very much appreciated.

I've been developing a server for a JavaScript/HTML 5 game for about 7 months now have you looked into Alchemy Websockets? its pretty easy to use.
Example:
using Alchemy;
using Alchemy.Classes;
namespace GameServer
{
static class Program
{
public static readonly ConcurrentDictionary<ClientPeer, bool> OnlineUsers = new ConcurrentDictionary<ClientPeer, bool>();
static void Main(string[] args)
{
var aServer = new WebSocketServer(4530, IPAddress.Any)
{
OnReceive = context => OnReceive(context),
OnConnected = context => OnConnect(context),
OnDisconnect = context => OnDisconnect(context),
TimeOut = new TimeSpan(0, 10, 0),
FlashAccessPolicyEnabled = true
};
}
private static void OnConnect(UserContext context)
{
var client = new ClientPeer(context);
OnlineUsers.TryAdd(client, false);
//Do something with the new client
}
}
}
As you can see its pretty easy to work with and I find their documentation very good (note ClientPeer is a custom class of mine just using it as an example).

What you are trying to achieve will be far easier if you take a look at ASP.NET SignalR
It has support for high level hubs to implement realtime communication and also has a persistent connection low level class to have a finely grained control over the communication.
Support for multiple client types and fallback if websockets isn't supported at both ends of the communication (it can optionally use long polling or forever frames).

The reason for this error is ( probably ) because you are not responding to the handshake. Once the connection is established browser sends some data and the server must respond appropriately ( otherwise browser will close the connection ). You can read more about this on wiki or directly in specification.

I modified a code i downloaded online and here's what I got now:
using System;
using System.Collections.Generic;
using System.Net.Sockets;
using System.Net;
using System.IO;
using System.Security.Cryptography;
using System.Threading;
namespace WebSocketServer
{
public enum ServerLogLevel { Nothing, Subtle, Verbose };
public delegate void ClientConnectedEventHandler(WebSocketConnection sender, EventArgs e);
public class WebSocketServer
{
#region private members
private string webSocketOrigin; // location for the protocol handshake
private string webSocketLocation; // location for the protocol handshake
#endregion
static private string guid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
static IPEndPoint ipLocal;
public event ClientConnectedEventHandler ClientConnected;
/// <summary>
/// TextWriter used for logging
/// </summary>
public TextWriter Logger { get; set; } // stream used for logging
/// <summary>
/// How much information do you want, the server to post to the stream
/// </summary>
public ServerLogLevel LogLevel = ServerLogLevel.Subtle;
/// <summary>
/// Gets the connections of the server
/// </summary>
public List<WebSocketConnection> Connections { get; private set; }
/// <summary>
/// Gets the listener socket. This socket is used to listen for new client connections
/// </summary>
public Socket ListenerSocker { get; private set; }
/// <summary>
/// Get the port of the server
/// </summary>
public int Port { get; private set; }
public WebSocketServer(int port, string origin, string location)
{
Port = port;
Connections = new List<WebSocketConnection>();
webSocketOrigin = origin;
webSocketLocation = location;
}
/// <summary>
/// Starts the server - making it listen for connections
/// </summary>
public void Start()
{
// create the main server socket, bind it to the local ip address and start listening for clients
ListenerSocker = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
ipLocal = new IPEndPoint(IPAddress.Loopback, Port);
ListenerSocker.Bind(ipLocal);
ListenerSocker.Listen(100);
LogLine(DateTime.Now + "> server stated on " + ListenerSocker.LocalEndPoint, ServerLogLevel.Subtle);
ListenForClients();
}
// look for connecting clients
private void ListenForClients()
{
ListenerSocker.BeginAccept(new AsyncCallback(OnClientConnect), null);
}
private void OnClientConnect(IAsyncResult asyn)
{
byte[] buffer = new byte[1024];
string headerResponse = "";
// create a new socket for the connection
var clientSocket = ListenerSocker.EndAccept(asyn);
var i = clientSocket.Receive(buffer);
headerResponse = (System.Text.Encoding.UTF8.GetString(buffer)).Substring(0, i);
//Console.WriteLine(headerResponse);
if (clientSocket != null)
{
// Console.WriteLine("HEADER RESPONSE:"+headerResponse);
var key = headerResponse.Replace("ey:", "`")
.Split('`')[1] // dGhlIHNhbXBsZSBub25jZQ== \r\n .......
.Replace("\r", "").Split('\n')[0] // dGhlIHNhbXBsZSBub25jZQ==
.Trim();
var test1 = AcceptKey(ref key);
var newLine = "\r\n";
var name = "Charmaine";
var response = "HTTP/1.1 101 Switching Protocols" + newLine
+ "Upgrade: websocket" + newLine
+ "Connection: Upgrade" + newLine
+ "Sec-WebSocket-Accept: " + test1 + newLine + newLine
+ "Testing lang naman po:" + name
;
// which one should I use? none of them fires the onopen method
clientSocket.Send(System.Text.Encoding.UTF8.GetBytes(response));
}
// keep track of the new guy
var clientConnection = new WebSocketConnection(clientSocket);
Connections.Add(clientConnection);
// clientConnection.Disconnected += new WebSocketDisconnectedEventHandler(ClientDisconnected);
Console.WriteLine("New user: " + ipLocal);
// invoke the connection event
if (ClientConnected != null)
ClientConnected(clientConnection, EventArgs.Empty);
if (LogLevel != ServerLogLevel.Nothing)
clientConnection.DataReceived += new DataReceivedEventHandler(DataReceivedFromClient);
// listen for more clients
ListenForClients();
}
void ClientDisconnected(WebSocketConnection sender, EventArgs e)
{
Connections.Remove(sender);
LogLine(DateTime.Now + "> " + sender.ConnectionSocket.LocalEndPoint + " disconnected", ServerLogLevel.Subtle);
}
void DataReceivedFromClient(WebSocketConnection sender, DataReceivedEventArgs e)
{
Log(DateTime.Now + "> data from " + sender.ConnectionSocket.LocalEndPoint, ServerLogLevel.Subtle);
Log(": " + e.Data + "\n" + e.Size + " bytes", ServerLogLevel.Verbose);
LogLine("", ServerLogLevel.Subtle);
}
/// <summary>
/// send a string to all the clients (you spammer!)
/// </summary>
/// <param name="data">the string to send</param>
public void SendToAll(string data)
{
Connections.ForEach(a => a.Send(data));
}
/// <summary>
/// send a string to all the clients except one
/// </summary>
/// <param name="data">the string to send</param>
/// <param name="indifferent">the client that doesn't care</param>
public void SendToAllExceptOne(string data, WebSocketConnection indifferent)
{
foreach (var client in Connections)
{
if (client != indifferent)
client.Send(data);
}
}
/// <summary>
/// Takes care of the initial handshaking between the the client and the server
/// </summary>
private void Log(string str, ServerLogLevel level)
{
if (Logger != null && (int)LogLevel >= (int)level)
{
Logger.Write(str);
}
}
private void LogLine(string str, ServerLogLevel level)
{
Log(str + "\r\n", level);
}
private static string AcceptKey(ref string key)
{
string longKey = key + guid;
byte[] hashBytes = ComputeHash(longKey);
return Convert.ToBase64String(hashBytes);
}
static SHA1 sha1 = SHA1CryptoServiceProvider.Create();
private static byte[] ComputeHash(string str)
{
return sha1.ComputeHash(System.Text.Encoding.ASCII.GetBytes(str));
}
private void ShakeHands(Socket conn)
{
using (var stream = new NetworkStream(conn))
using (var reader = new StreamReader(stream))
using (var writer = new StreamWriter(stream))
{
//read handshake from client (no need to actually read it, we know its there):
LogLine("Reading client handshake:", ServerLogLevel.Verbose);
string r = null;
while (r != "")
{
r = reader.ReadLine();
LogLine(r, ServerLogLevel.Verbose);
}
// send handshake to the client
writer.WriteLine("HTTP/1.1 101 Web Socket Protocol Handshake");
writer.WriteLine("Upgrade: WebSocket");
writer.WriteLine("Connection: Upgrade");
writer.WriteLine("WebSocket-Origin: " + webSocketOrigin);
writer.WriteLine("WebSocket-Location: " + webSocketLocation);
writer.WriteLine("");
}
// tell the nerds whats going on
LogLine("Sending handshake:", ServerLogLevel.Verbose);
LogLine("HTTP/1.1 101 Web Socket Protocol Handshake", ServerLogLevel.Verbose);
LogLine("Upgrade: WebSocket", ServerLogLevel.Verbose);
LogLine("Connection: Upgrade", ServerLogLevel.Verbose);
LogLine("WebSocket-Origin: " + webSocketOrigin, ServerLogLevel.Verbose);
LogLine("WebSocket-Location: " + webSocketLocation, ServerLogLevel.Verbose);
LogLine("", ServerLogLevel.Verbose);
LogLine("Started listening to client", ServerLogLevel.Verbose);
//conn.Listen();
}
}
}
Connection issue resolved, next would be SENDING DATA to client.

just change shakehands in WebSocketServer.cs file in solution with below code and your error will gone..
private void ShakeHands(Socket conn)
{
using (var stream = new NetworkStream(conn))
using (var reader = new StreamReader(stream))
using (var writer = new StreamWriter(stream))
{
//read handshake from client (no need to actually read it, we know its there):
LogLine("Reading client handshake:", ServerLogLevel.Verbose);
string r = null;
Dictionary<string, string> headers = new Dictionary<string, string>();
while (r != "")
{
r = reader.ReadLine();
string[] tokens = r.Split(new char[] { ':' }, 2);
if (!string.IsNullOrWhiteSpace(r) && tokens.Length > 1)
{
headers[tokens[0]] = tokens[1].Trim();
}
LogLine(r, ServerLogLevel.Verbose);
}
//string line = string.Empty;
//while ((line = reader.ReadLine()) != string.Empty)
//{
// string[] tokens = line.Split(new char[] { ':' }, 2);
// if (!string.IsNullOrWhiteSpace(line) && tokens.Length > 1)
// {
// headers[tokens[0]] = tokens[1].Trim();
// }
//}
string responseKey = "";
string key = string.Concat(headers["Sec-WebSocket-Key"], "258EAFA5-E914-47DA-95CA-C5AB0DC85B11");
using (SHA1 sha1 = SHA1.Create())
{
byte[] hash = sha1.ComputeHash(Encoding.UTF8.GetBytes(key));
responseKey = Convert.ToBase64String(hash);
}
// send handshake to the client
writer.WriteLine("HTTP/1.1 101 Web Socket Protocol Handshake");
writer.WriteLine("Upgrade: WebSocket");
writer.WriteLine("Connection: Upgrade");
writer.WriteLine("WebSocket-Origin: " + webSocketOrigin);
writer.WriteLine("WebSocket-Location: " + webSocketLocation);
//writer.WriteLine("Sec-WebSocket-Protocol: chat");
writer.WriteLine("Sec-WebSocket-Accept: " + responseKey);
writer.WriteLine("");
}
// tell the nerds whats going on
LogLine("Sending handshake:", ServerLogLevel.Verbose);
LogLine("HTTP/1.1 101 Web Socket Protocol Handshake", ServerLogLevel.Verbose);
LogLine("Upgrade: WebSocket", ServerLogLevel.Verbose);
LogLine("Connection: Upgrade", ServerLogLevel.Verbose);
LogLine("WebSocket-Origin: " + webSocketOrigin, ServerLogLevel.Verbose);
LogLine("WebSocket-Location: " + webSocketLocation, ServerLogLevel.Verbose);
LogLine("", ServerLogLevel.Verbose);
LogLine("Started listening to client", ServerLogLevel.Verbose);
//conn.Listen();
}

You may also take a look at the WebSocketRPC library which should be pretty simple to use, for both the "raw" connection and the RPC connections (the messages can also be mixed).
The following can be useful to you:
The code responsible for sending/receiving raw messages is located in the Connection class.
In the repository you can also find how a base JavaScript client is implemented.
Disclaimer: I am the author.

UDP hole punching implementation

I am trying to accomplish UDP hole punching. I am basing my theory on this article and this WIKI page, but I am facing some issues with the C# coding of it. Here is my problem:
Using the code that was posted here I am now able to connect to a remote machine and listen on the same port for incoming connections (Bind 2 UDP clients to the same port).
For some reason the two bindings to the same port block each other from receiving any data.
I have a UDP server that responds to my connection so if I connect to it first before binding any other client to the port I get its responses back.
If I bind another client to the port no data will be received on either clients.
Following are 2 code pieces that show my problem. The first connects to a remote server to create the rule on the NAT device and then a listener is started on a different thread to capture the incoming packets. The code then sends packets to the local IP so that the listener will get it. The second only sends packets to the local IP to make sure this works. I know this is not the actual hole punching as I am sending the packets to myself without living the NAT device at all. I am facing a problem at this point, and I don't imagine this will be any different if I use a computer out side the NAT device to connect.
[EDIT] 2/4/2012
I tried using another computer on my network and WireShark (packet sniffer) to test the listener. I see the packets incoming from the other computer but are not received by the listener UDP client (udpServer) or the sender UDP client (client).
[EDIT] 2/5/2010
I have now added a function call to close the first UDP client after the initial sending and receiving of packets only living the second UDP client to listen on the port. This works and I can receive packets from inside the network on that port. I will now try to send and receive packets from outside the network. I will post my findings as soon as I find something.
Using this code I get data on the listening client:
static void Main(string[] args)
{
IPEndPoint localpt = new IPEndPoint(Dns.Resolve(Dns.GetHostName()).AddressList[0], 4545);
ThreadPool.QueueUserWorkItem(delegate
{
UdpClient udpServer = new UdpClient();
udpServer.ExclusiveAddressUse = false;
udpServer.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
udpServer.Client.Bind(localpt);
IPEndPoint inEndPoint = new IPEndPoint(IPAddress.Any, 0);
Console.WriteLine("Listening on " + localpt + ".");
byte[] buffer = udpServer.Receive(ref inEndPoint); //this line will block forever
Console.WriteLine("Receive from " + inEndPoint + " " + Encoding.ASCII.GetString(buffer) + ".");
});
Thread.Sleep(1000);
UdpClient udpServer2 = new UdpClient(6000);
// the following lines work and the data is received
udpServer2.Connect(Dns.Resolve(Dns.GetHostName()).AddressList[0], 4545);
udpServer2.Send(new byte[] { 0x41 }, 1);
Console.Read();
}
If I use the following code, after the connection and data transfer between my client and server, the listening UDP client will not receive anything:
static void Main(string[] args)
{
IPEndPoint localpt = new IPEndPoint(Dns.Resolve(Dns.GetHostName()).AddressList[0], 4545);
//if the following lines up until serverConnect(); are removed all packets are received correctly
client = new UdpClient();
client.ExclusiveAddressUse = false;
client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
client.Client.Bind(localpt);
remoteServerConnect(); //connection to remote server is done here
//response is received correctly and printed to the console
ThreadPool.QueueUserWorkItem(delegate
{
UdpClient udpServer = new UdpClient();
udpServer.ExclusiveAddressUse = false;
udpServer.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
udpServer.Client.Bind(localpt);
IPEndPoint inEndPoint = new IPEndPoint(IPAddress.Any, 0);
Console.WriteLine("Listening on " + localpt + ".");
byte[] buffer = udpServer.Receive(ref inEndPoint); //this line will block forever
Console.WriteLine("Receive from " + inEndPoint + " " + Encoding.ASCII.GetString(buffer) + ".");
});
Thread.Sleep(1000);
UdpClient udpServer2 = new UdpClient(6000);
// I expected the following line to work and to receive this as well
udpServer2.Connect(Dns.Resolve(Dns.GetHostName()).AddressList[0], 4545);
udpServer2.Send(new byte[] { 0x41 }, 1);
Console.Read();
}

If i understand correctly, you are trying to communicate peer-to-peer between 2 clients each behind a different NAT, using a mediation server for hole punching?
Few years ago i did the exact same thing in c#, i haven't found the code yet, but ill give you some pointers if you like:
First, I wouldn't use the Connect() function on the udpclient, since UDP is a connectionless protocol, all this function really does is hide the functionality of a UDP socket.
You should perfrom the following steps:
Open a UDP socket on a server with it's ports not blocked by a firewall, at a specific port (eg Bind this socket to a chosen port for example 23000)
Create a UDP socket on the first client, and send something to the server at 23000. Do not bind this socket. When a udp is used to send a packet, windows will automatically assign a free port to the socket
Do the same from the other client
The server has now received 2 packets from 2 clients at 2 different adresses with 2 different ports. Test if the server can send packets back on the same address and port. (If this doesn't work you did something wrong or your NAT isn't working. You know its working if you can play games without opening ports :D)
The server should now send the address and port of the other clients to each connected client.
A client should now be able to send packets using UDP to the adresses received from the server.
You should note that the port used on the nat is probably not the same port as on your client pc!! The server should distribute this external port to clients. You must use the external adresses and the external ports to send to!
Also note that your NAT might not support this kind of port forwarding. Some NAT's forward all incoming traffic on a assigned port to you client, which is what you want. But some nats do filtering on the incoming packets adresses so it might block the other clients packets. This is unlikely though when using a standard personal user router.

Edit: After a lot more testing this doesn't seem to work at all for me unless I enable UPnP. So a lot of the things I wrote here you may find useful but many people don't have UPnP enabled (because it is a security risk) so it will not work for them.
Here is some code using PubNub as a relay server :). I don't recommend using this code without testing because it is not perfect (I'm not sure if it is even secure or the right way to do things? idk I'm not a networking expert) but it should give you an idea of what to do. It at least has worked for me so far in a hobby project. The things it is missing are:
Testing if the client is on your LAN. I just send to both which works for your LAN and a device on another network but that is very inefficient.
Testing when the client stops listening if, for example, they closed the program. Because this is UDP it is stateless so it doesn't matter if we are sending messages into the void but we probably shouldn't do that if noone is getting them
I use Open.NAT to do port forwarding programatically but this might not work on some devices. Specifically, it uses UPnP which is a little insecure and requires UDP port 1900 to be port forwarded manually. Once they do this it is supported on most routers but many have not done this yet.
So first of all, you need a way to get your external and local IPs. Here is code for getting your local IP:
// From http://stackoverflow.com/questions/6803073/get-local-ip-address
public string GetLocalIp()
{
var host = Dns.GetHostEntry(Dns.GetHostName());
foreach (var ip in host.AddressList)
{
if (ip.AddressFamily == AddressFamily.InterNetwork)
{
return ip.ToString();
}
}
throw new Exception("Failed to get local IP");
}
And here is some code for getting your external IP via trying a few websites that are designed to return your external IP
public string GetExternalIp()
{
for (int i = 0; i < 2; i++)
{
string res = GetExternalIpWithTimeout(400);
if (res != "")
{
return res;
}
}
throw new Exception("Failed to get external IP");
}
private static string GetExternalIpWithTimeout(int timeoutMillis)
{
string[] sites = new string[] {
"http://ipinfo.io/ip",
"http://icanhazip.com/",
"http://ipof.in/txt",
"http://ifconfig.me/ip",
"http://ipecho.net/plain"
};
foreach (string site in sites)
{
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(site);
request.Timeout = timeoutMillis;
using (var webResponse = (HttpWebResponse)request.GetResponse())
{
using (Stream responseStream = webResponse.GetResponseStream())
{
using (StreamReader responseReader = new System.IO.StreamReader(responseStream, Encoding.UTF8))
{
return responseReader.ReadToEnd().Trim();
}
}
}
}
catch
{
continue;
}
}
return "";
}
Now we need to find an open port and forward it to an external port. As mentioned above I used Open.NAT. First, you put together a list of ports that you think would be reasonable for your application to use after looking at registered UDP ports. Here are a few for example:
public static int[] ports = new int[]
{
5283,
5284,
5285,
5286,
5287,
5288,
5289,
5290,
5291,
5292,
5293,
5294,
5295,
5296,
5297
};
Now we can loop through them and hopefully find one that is not in use to use port forwarding on:
public UdpClient GetUDPClientFromPorts(out Socket portHolder, out string localIp, out int localPort, out string externalIp, out int externalPort)
{
localIp = GetLocalIp();
externalIp = GetExternalIp();
var discoverer = new Open.Nat.NatDiscoverer();
var device = discoverer.DiscoverDeviceAsync().Result;
IPAddress localAddr = IPAddress.Parse(localIp);
int workingPort = -1;
for (int i = 0; i < ports.Length; i++)
{
try
{
// You can alternatively test tcp with nc -vz externalip 5293 in linux and
// udp with nc -vz -u externalip 5293 in linux
Socket tempServer = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
tempServer.Bind(new IPEndPoint(localAddr, ports[i]));
tempServer.Close();
workingPort = ports[i];
break;
}
catch
{
// Binding failed, port is in use, try next one
}
}
if (workingPort == -1)
{
throw new Exception("Failed to connect to a port");
}
int localPort = workingPort;
// You could try a different external port if the below code doesn't work
externalPort = workingPort;
// Mapping ports
device.CreatePortMapAsync(new Open.Nat.Mapping(Open.Nat.Protocol.Udp, localPort, externalPort));
// Bind a socket to our port to "claim" it or cry if someone else is now using it
try
{
portHolder = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
portHolder.Bind(new IPEndPoint(localAddr, localPort));
}
catch
{
throw new Exception("Failed, someone is now using local port: " + localPort);
}
// Make a UDP Client that will use that port
UdpClient udpClient = new UdpClient(localPort);
return udpClient;
}
Now for the PubNub relay server code (P2PPeer will be defined later below). There is a lot here so I'm not really gonna explain it but hopefully the code is clear enough to help you understand what is going on
public delegate void NewPeerCallback(P2PPeer newPeer);
public event NewPeerCallback OnNewPeerConnection;
public Pubnub pubnub;
public string pubnubChannelName;
public string localIp;
public string externalIp;
public int localPort;
public int externalPort;
public UdpClient udpClient;
HashSet<string> uniqueIdsPubNubSeen;
object peerLock = new object();
Dictionary<string, P2PPeer> connectedPeers;
string myPeerDataString;
public void InitPubnub(string pubnubPublishKey, string pubnubSubscribeKey, string pubnubChannelName)
{
uniqueIdsPubNubSeen = new HashSet<string>();
connectedPeers = new Dictionary<string, P2PPeer>;
pubnub = new Pubnub(pubnubPublishKey, pubnubSubscribeKey);
myPeerDataString = localIp + " " + externalIp + " " + localPort + " " + externalPort + " " + pubnub.SessionUUID;
this.pubnubChannelName = pubnubChannelName;
pubnub.Subscribe<string>(
pubnubChannelName,
OnPubNubMessage,
OnPubNubConnect,
OnPubNubError);
return pubnub;
}
//// Subscribe callbacks
void OnPubNubConnect(string res)
{
pubnub.Publish<string>(pubnubChannelName, connectionDataString, OnPubNubTheyGotMessage, OnPubNubMessageFailed);
}
void OnPubNubError(PubnubClientError clientError)
{
throw new Exception("PubNub error on subscribe: " + clientError.Message);
}
void OnPubNubMessage(string message)
{
// The message will be the string ["localIp externalIp localPort externalPort","messageId","channelName"]
string[] splitMessage = message.Trim().Substring(1, message.Length - 2).Split(new char[] { ',' });
string peerDataString = splitMessage[0].Trim().Substring(1, splitMessage[0].Trim().Length - 2);
// If you want these, I don't need them
//string peerMessageId = splitMessage[1].Trim().Substring(1, splitMessage[1].Trim().Length - 2);
//string channelName = splitMessage[2].Trim().Substring(1, splitMessage[2].Trim().Length - 2);
string[] pieces = peerDataString.Split(new char[] { ' ', '\t' });
string peerLocalIp = pieces[0].Trim();
string peerExternalIp = pieces[1].Trim();
string peerLocalPort = int.Parse(pieces[2].Trim());
string peerExternalPort = int.Parse(pieces[3].Trim());
string peerPubnubUniqueId = pieces[4].Trim();
pubNubUniqueId = pieces[4].Trim();
// If you are on the same device then you have to do this for it to work idk why
if (peerLocalIp == localIp && peerExternalIp == externalIp)
{
peerLocalIp = "127.0.0.1";
}
// From me, ignore
if (peerPubnubUniqueId == pubnub.SessionUUID)
{
return;
}
// We haven't set up our connection yet, what are we doing
if (udpClient == null)
{
return;
}
// From someone else
IPEndPoint peerEndPoint = new IPEndPoint(IPAddress.Parse(peerExternalIp), peerExternalPort);
IPEndPoint peerEndPointLocal = new IPEndPoint(IPAddress.Parse(peerLocalIp), peerLocalPort);
// First time we have heard from them
if (!uniqueIdsPubNubSeen.Contains(peerPubnubUniqueId))
{
uniqueIdsPubNubSeen.Add(peerPubnubUniqueId);
// Dummy messages to do UDP hole punching, these may or may not go through and that is fine
udpClient.Send(new byte[10], 10, peerEndPoint);
udpClient.Send(new byte[10], 10, peerEndPointLocal); // This is if they are on a LAN, we will try both
pubnub.Publish<string>(pubnubChannelName, myPeerDataString, OnPubNubTheyGotMessage, OnPubNubMessageFailed);
}
// Second time we have heard from them, after then we don't care because we are connected
else if (!connectedPeers.ContainsKey(peerPubnubUniqueId))
{
//bool isOnLan = IsOnLan(IPAddress.Parse(peerExternalIp)); TODO, this would be nice to test for
bool isOnLan = false; // For now we will just do things for both
P2PPeer peer = new P2PPeer(peerLocalIp, peerExternalIp, peerLocalPort, peerExternalPort, this, isOnLan);
lock (peerLock)
{
connectedPeers.Add(peerPubnubUniqueId, peer);
}
// More dummy messages because why not
udpClient.Send(new byte[10], 10, peerEndPoint);
udpClient.Send(new byte[10], 10, peerEndPointLocal);
pubnub.Publish<string>(pubnubChannelName, connectionDataString, OnPubNubTheyGotMessage, OnPubNubMessageFailed);
if (OnNewPeerConnection != null)
{
OnNewPeerConnection(peer);
}
}
}
//// Publish callbacks
void OnPubNubTheyGotMessage(object result)
{
}
void OnPubNubMessageFailed(PubnubClientError clientError)
{
throw new Exception("PubNub error on publish: " + clientError.Message);
}
And here is a P2PPeer
public class P2PPeer
{
public string localIp;
public string externalIp;
public int localPort;
public int externalPort;
public bool isOnLan;
P2PClient client;
public delegate void ReceivedBytesFromPeerCallback(byte[] bytes);
public event ReceivedBytesFromPeerCallback OnReceivedBytesFromPeer;
public P2PPeer(string localIp, string externalIp, int localPort, int externalPort, P2PClient client, bool isOnLan)
{
this.localIp = localIp;
this.externalIp = externalIp;
this.localPort = localPort;
this.externalPort = externalPort;
this.client = client;
this.isOnLan = isOnLan;
if (isOnLan)
{
IPEndPoint endPointLocal = new IPEndPoint(IPAddress.Parse(localIp), localPort);
Thread localListener = new Thread(() => ReceiveMessage(endPointLocal));
localListener.IsBackground = true;
localListener.Start();
}
else
{
IPEndPoint endPoint = new IPEndPoint(IPAddress.Parse(externalIp), externalPort);
Thread externalListener = new Thread(() => ReceiveMessage(endPoint));
externalListener.IsBackground = true;
externalListener.Start();
}
}
public void SendBytes(byte[] data)
{
if (client.udpClient == null)
{
throw new Exception("P2PClient doesn't have a udpSocket open anymore");
}
//if (isOnLan) // This would work but I'm not sure how to test if they are on LAN so I'll just use both for now
{
client.udpClient.Send(data, data.Length, new IPEndPoint(IPAddress.Parse(localIp), localPort));
}
//else
{
client.udpClient.Send(data, data.Length, new IPEndPoint(IPAddress.Parse(externalIp), externalPort));
}
}
// Encoded in UTF8
public void SendString(string str)
{
SendBytes(System.Text.Encoding.UTF8.GetBytes(str));
}
void ReceiveMessage(IPEndPoint endPoint)
{
while (client.udpClient != null)
{
byte[] message = client.udpClient.Receive(ref endPoint);
if (OnReceivedBytesFromPeer != null)
{
OnReceivedBytesFromPeer(message);
}
//string receiveString = Encoding.UTF8.GetString(message);
//Console.Log("got: " + receiveString);
}
}
}
Finally, here are all my usings:
using PubNubMessaging.Core; // Get from PubNub GitHub for C#, I used the Unity3D library
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
I'm open to comments and questions, feel free to give feedback if something here is bad practice or doesn't work. A few bugs were introduced in translation from my code that I'll fix here eventually but this should at least give you the idea of what to do.

Have you tried using the Async functions, here is a example of how you might get it to work it may need a bit of work to make it 100% functional:
public void HolePunch(String ServerIp, Int32 Port)
{
IPEndPoint LocalPt = new IPEndPoint(Dns.GetHostEntry(Dns.GetHostName()).AddressList[0], Port);
UdpClient Client = new UdpClient();
Client.ExclusiveAddressUse = false;
Client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
Client.Client.Bind(LocalPt);
IPEndPoint RemotePt = new IPEndPoint(IPAddress.Parse(ServerIp), Port);
// This Part Sends your local endpoint to the server so if the two peers are on the same nat they can bypass it, you can omit this if you wish to just use the remote endpoint.
byte[] IPBuffer = System.Text.Encoding.UTF8.GetBytes(Dns.GetHostEntry(Dns.GetHostName()).AddressList[0].ToString());
byte[] LengthBuffer = BitConverter.GetBytes(IPBuffer.Length);
byte[] PortBuffer = BitConverter.GetBytes(Port);
byte[] Buffer = new byte[IPBuffer.Length + LengthBuffer.Length + PortBuffer.Length];
LengthBuffer.CopyTo(Buffer,0);
IPBuffer.CopyTo(Buffer, LengthBuffer.Length);
PortBuffer.CopyTo(Buffer, IPBuffer.Length + LengthBuffer.Length);
Client.BeginSend(Buffer, Buffer.Length, RemotePt, new AsyncCallback(SendCallback), Client);
// Wait to receve something
BeginReceive(Client, Port);
// you may want to use a auto or manual ResetEvent here and have the server send back a confirmation, the server should have now stored your local (you sent it) and remote endpoint.
// you now need to work out who you need to connect to then ask the server for there remote and local end point then need to try to connect to the local first then the remote.
// if the server knows who you need to connect to you could just have it send you the endpoints as the confirmation.
// you may also need to keep this open with a keepalive packet untill it is time to connect to the peer or peers.
// once you have the endpoints of the peer you can close this connection unless you need to keep asking the server for other endpoints
Client.Close();
}
public void ConnectToPeer(String PeerIp, Int32 Port)
{
IPEndPoint LocalPt = new IPEndPoint(Dns.GetHostEntry(Dns.GetHostName()).AddressList[0], Port);
UdpClient Client = new UdpClient();
Client.ExclusiveAddressUse = false;
Client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
Client.Client.Bind(LocalPt);
IPEndPoint RemotePt = new IPEndPoint(IPAddress.Parse(PeerIp), Port);
Client.Connect(RemotePt);
//you may want to keep the peer client connections in a list.
BeginReceive(Client, Port);
}
public void SendCallback(IAsyncResult ar)
{
UdpClient Client = (UdpClient)ar.AsyncState;
Client.EndSend(ar);
}
public void BeginReceive(UdpClient Client, Int32 Port)
{
IPEndPoint ListenPt = new IPEndPoint(IPAddress.Any, Port);
Object[] State = new Object[] { Client, ListenPt };
Client.BeginReceive(new AsyncCallback(ReceiveCallback), State);
}
public void ReceiveCallback(IAsyncResult ar)
{
UdpClient Client = (UdpClient)((Object[])ar.AsyncState)[0];
IPEndPoint ListenPt = (IPEndPoint)((Object[])ar.AsyncState)[0];
Byte[] receiveBytes = Client.EndReceive(ar, ref ListenPt);
}
I hope this helps.

Update:
Whichever of the UdpClients binds first is the one that will be sent incoming packets by Windows. In your example try moving the code block that sets up the listening thread to the top.
Are you sure the problem is not just that the receive thread is only written to handle a single receive? Try replacing the receive thread with as below.
ThreadPool.QueueUserWorkItem(delegate
{
UdpClient udpServer = new UdpClient();
udpServer.ExclusiveAddressUse = false;
udpServer.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
udpServer.Client.Bind(localpt);
IPEndPoint inEndPoint = new IPEndPoint(IPAddress.Any, 0);
Console.WriteLine("Listening on " + localpt + ".");
while (inEndPoint != null)
{
byte[] buffer = udpServer.Receive(ref inEndPoint);
Console.WriteLine("Bytes received from " + inEndPoint + " " + Encoding.ASCII.GetString(buffer) + ".");
}
});

Sorry for uploading such a huge piece of code, but i guess this is very clearly explains how things work, and may be really useful. If you will have issues with this code, please let me know.
Note:
this is just a draft
(important) you MUST inform server with your local endpoint. if you will not do it you will not be able to communicate between two peers behind one NAT (for example, on one local machine) even if the server is out of NAT
you must close "puncher" client (at least, i did not manage to receive any packets until i did it). later you will be able to communicate with server using other UdpClient's
of cource it will not work with symmetric NAT
if you find that something in this code is "terrible practice", please tell me, i'm not network expert :)
Server.cs
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using HolePunching.Common;
namespace HolePunching.Server
{
class Server
{
private static bool _isRunning;
private static UdpClient _udpClient;
private static readonly Dictionary<byte, PeerContext> Contexts = new Dictionary<byte, PeerContext>();
private static readonly Dictionary<byte, byte> Mappings = new Dictionary<byte, byte>
{
{1, 2},
{2, 1},
};
static void Main()
{
_udpClient = new UdpClient( Consts.UdpPort );
ListenUdp();
Console.ReadLine();
_isRunning = false;
}
private static async void ListenUdp()
{
_isRunning = true;
while ( _isRunning )
{
try
{
var receivedResults = await _udpClient.ReceiveAsync();
if ( !_isRunning )
{
break;
}
ProcessUdpMessage( receivedResults.Buffer, receivedResults.RemoteEndPoint );
}
catch ( Exception ex )
{
Console.WriteLine( $"Error: {ex.Message}" );
}
}
}
private static void ProcessUdpMessage( byte[] buffer, IPEndPoint remoteEndPoint )
{
if ( !UdpProtocol.UdpInfoMessage.TryParse( buffer, out UdpProtocol.UdpInfoMessage message ) )
{
Console.WriteLine( $" >>> Got shitty UDP [ {remoteEndPoint.Address} : {remoteEndPoint.Port} ]" );
_udpClient.Send( new byte[] { 1 }, 1, remoteEndPoint );
return;
}
Console.WriteLine( $" >>> Got UDP from {message.Id}. [ {remoteEndPoint.Address} : {remoteEndPoint.Port} ]" );
if ( !Contexts.TryGetValue( message.Id, out PeerContext context ) )
{
context = new PeerContext
{
PeerId = message.Id,
PublicUdpEndPoint = remoteEndPoint,
LocalUdpEndPoint = new IPEndPoint( message.LocalIp, message.LocalPort ),
};
Contexts.Add( context.PeerId, context );
}
byte partnerId = Mappings[context.PeerId];
if ( !Contexts.TryGetValue( partnerId, out context ) )
{
_udpClient.Send( new byte[] { 1 }, 1, remoteEndPoint );
return;
}
var response = UdpProtocol.PeerAddressMessage.GetMessage(
partnerId,
context.PublicUdpEndPoint.Address,
context.PublicUdpEndPoint.Port,
context.LocalUdpEndPoint.Address,
context.LocalUdpEndPoint.Port );
_udpClient.Send( response.Data, response.Data.Length, remoteEndPoint );
Console.WriteLine( $" <<< Responsed to {message.Id}" );
}
}
public class PeerContext
{
public byte PeerId { get; set; }
public IPEndPoint PublicUdpEndPoint { get; set; }
public IPEndPoint LocalUdpEndPoint { get; set; }
}
}
Client.cs
using System;
namespace HolePunching.Client
{
class Client
{
public const string ServerIp = "your.server.public.address";
static void Main()
{
byte id = ReadIdFromConsole();
// you need some smarter :)
int localPort = id == 1 ? 61043 : 59912;
var x = new Demo( ServerIp, id, localPort );
x.Start();
}
private static byte ReadIdFromConsole()
{
Console.Write( "Peer id (1 or 2): " );
var id = byte.Parse( Console.ReadLine() );
Console.Title = $"Peer {id}";
return id;
}
}
}
Demo.cs
using HolePunching.Common;
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;
namespace HolePunching.Client
{
public class Demo
{
private static bool _isRunning;
private static UdpClient _udpPuncher;
private static UdpClient _udpClient;
private static UdpClient _extraUdpClient;
private static bool _extraUdpClientConnected;
private static byte _id;
private static IPEndPoint _localEndPoint;
private static IPEndPoint _serverUdpEndPoint;
private static IPEndPoint _partnerPublicUdpEndPoint;
private static IPEndPoint _partnerLocalUdpEndPoint;
private static string GetLocalIp()
{
var host = Dns.GetHostEntry( Dns.GetHostName() );
foreach ( var ip in host.AddressList )
{
if ( ip.AddressFamily == AddressFamily.InterNetwork )
{
return ip.ToString();
}
}
throw new Exception( "Failed to get local IP" );
}
public Demo( string serverIp, byte id, int localPort )
{
_serverUdpEndPoint = new IPEndPoint( IPAddress.Parse( serverIp ), Consts.UdpPort );
_id = id;
// we have to bind all our UdpClients to this endpoint
_localEndPoint = new IPEndPoint( IPAddress.Parse( GetLocalIp() ), localPort );
}
public void Start( )
{
_udpPuncher = new UdpClient(); // this guy is just for punching
_udpClient = new UdpClient(); // this will keep hole alive, and also can send data
_extraUdpClient = new UdpClient(); // i think, this guy is the best option for sending data (explained below)
InitUdpClients( new[] { _udpPuncher, _udpClient, _extraUdpClient }, _localEndPoint );
Task.Run( (Action) SendUdpMessages );
Task.Run( (Action) ListenUdp );
Console.ReadLine();
_isRunning = false;
}
private void InitUdpClients(IEnumerable<UdpClient> clients, EndPoint localEndPoint)
{
// if you don't want to use explicit localPort, you should create here one more UdpClient (X) and send something to server (it will automatically bind X to free port). then bind all clients to this port and close X
foreach ( var udpClient in clients )
{
udpClient.ExclusiveAddressUse = false;
udpClient.Client.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true );
udpClient.Client.Bind( localEndPoint );
}
}
private void SendUdpMessages()
{
_isRunning = true;
var messageToServer = UdpProtocol.UdpInfoMessage.GetMessage( _id, _localEndPoint.Address, _localEndPoint.Port );
var messageToPeer = UdpProtocol.P2PKeepAliveMessage.GetMessage();
while ( _isRunning )
{
// while we dont have partner's address, we will send messages to server
if ( _partnerPublicUdpEndPoint == null && _partnerLocalUdpEndPoint == null )
{
_udpPuncher.Send( messageToServer.Data, messageToServer.Data.Length, _serverUdpEndPoint );
Console.WriteLine( $" >>> Sent UDP to server [ {_serverUdpEndPoint.Address} : {_serverUdpEndPoint.Port} ]" );
}
else
{
// you can skip it. just demonstration, that you still can send messages to server
_udpClient.Send( messageToServer.Data, messageToServer.Data.Length, _serverUdpEndPoint );
Console.WriteLine( $" >>> Sent UDP to server [ {_serverUdpEndPoint.Address} : {_serverUdpEndPoint.Port} ]" );
// THIS is how we punching hole! very first this message should be dropped by partner's NAT, but it's ok.
// i suppose that this is good idea to send this "keep-alive" messages to peer even if you are connected already,
// because AFAIK "hole" for UDP lives ~2 minutes on NAT. so "we will let it die? NEVER!" (c)
_udpClient.Send( messageToPeer.Data, messageToPeer.Data.Length, _partnerPublicUdpEndPoint );
_udpClient.Send( messageToPeer.Data, messageToPeer.Data.Length, _partnerLocalUdpEndPoint );
Console.WriteLine( $" >>> Sent UDP to peer.public [ {_partnerPublicUdpEndPoint.Address} : {_partnerPublicUdpEndPoint.Port} ]" );
Console.WriteLine( $" >>> Sent UDP to peer.local [ {_partnerLocalUdpEndPoint.Address} : {_partnerLocalUdpEndPoint.Port} ]" );
// "connected" UdpClient sends data much faster,
// so if you have something that your partner cant wait for (voice, for example), send it this way
if ( _extraUdpClientConnected )
{
_extraUdpClient.Send( messageToPeer.Data, messageToPeer.Data.Length );
Console.WriteLine( $" >>> Sent UDP to peer.received EP" );
}
}
Thread.Sleep( 3000 );
}
}
private async void ListenUdp()
{
_isRunning = true;
while ( _isRunning )
{
try
{
// also important thing!
// when you did not punched hole yet, you must listen incoming packets using "puncher" (later we will close it).
// where you already have p2p connection (and "puncher" closed), use "non-puncher"
UdpClient udpClient = _partnerPublicUdpEndPoint == null ? _udpPuncher : _udpClient;
var receivedResults = await udpClient.ReceiveAsync();
if ( !_isRunning )
{
break;
}
ProcessUdpMessage( receivedResults.Buffer, receivedResults.RemoteEndPoint );
}
catch ( SocketException ex )
{
// do something here...
}
catch ( Exception ex )
{
Console.WriteLine( $"Error: {ex.Message}" );
}
}
}
private static void ProcessUdpMessage( byte[] buffer, IPEndPoint remoteEndPoint )
{
// if server sent partner's endpoinps, we will store it and (IMPORTANT) close "puncher"
if ( UdpProtocol.PeerAddressMessage.TryParse( buffer, out UdpProtocol.PeerAddressMessage peerAddressMessage ) )
{
Console.WriteLine( " <<< Got response from server" );
_partnerPublicUdpEndPoint = new IPEndPoint( peerAddressMessage.PublicIp, peerAddressMessage.PublicPort );
_partnerLocalUdpEndPoint = new IPEndPoint( peerAddressMessage.LocalIp, peerAddressMessage.LocalPort );
_udpPuncher.Close();
}
// since we got this message we know partner's endpoint for sure,
// and we can "connect" UdpClient to it, so it will work faster
else if ( UdpProtocol.P2PKeepAliveMessage.TryParse( buffer ) )
{
Console.WriteLine( $" IT WORKS!!! WOW!!! [ {remoteEndPoint.Address} : {remoteEndPoint.Port} ]" );
_extraUdpClientConnected = true;
_extraUdpClient.Connect( remoteEndPoint );
}
else
{
Console.WriteLine( "???" );
}
}
}
}
Protocol.cs
I'm not sure how good this approach, maybe something like protobuf can do it better
using System;
using System.Linq;
using System.Net;
using System.Text;
namespace HolePunching.Common
{
public static class UdpProtocol
{
public static readonly int GuidLength = 16;
public static readonly int PeerIdLength = 1;
public static readonly int IpLength = 4;
public static readonly int IntLength = 4;
public static readonly byte[] Prefix = { 12, 23, 34, 45 };
private static byte[] JoinBytes( params byte[][] bytes )
{
var result = new byte[bytes.Sum( x => x.Length )];
int pos = 0;
for ( int i = 0; i < bytes.Length; i++ )
{
for ( int j = 0; j < bytes[i].Length; j++, pos++ )
{
result[pos] = bytes[i][j];
}
}
return result;
}
#region Helper extensions
private static bool StartsWith( this byte[] #this, byte[] value, int offset = 0 )
{
if ( #this == null || value == null || #this.Length < offset + value.Length )
{
return false;
}
for ( int i = 0; i < value.Length; i++ )
{
if ( #this[i + offset] < value[i] )
{
return false;
}
}
return true;
}
private static byte[] ToUnicodeBytes( this string #this )
{
return Encoding.Unicode.GetBytes( #this );
}
private static byte[] Take( this byte[] #this, int offset, int length )
{
return #this.Skip( offset ).Take( length ).ToArray();
}
public static bool IsSuitableUdpMessage( this byte[] #this )
{
return #this.StartsWith( Prefix );
}
public static int GetInt( this byte[] #this )
{
if ( #this.Length != 4 )
throw new ArgumentException( "Byte array must be exactly 4 bytes to be convertible to uint." );
return ( ( ( #this[0] << 8 ) + #this[1] << 8 ) + #this[2] << 8 ) + #this[3];
}
public static byte[] ToByteArray( this int value )
{
return new[]
{
(byte)(value >> 24),
(byte)(value >> 16),
(byte)(value >> 8),
(byte)value
};
}
#endregion
#region Messages
public abstract class UdpMessage
{
public byte[] Data { get; }
protected UdpMessage( byte[] data )
{
Data = data;
}
}
public class UdpInfoMessage : UdpMessage
{
private static readonly byte[] MessagePrefix = { 41, 57 };
private static readonly int MessageLength = Prefix.Length + MessagePrefix.Length + PeerIdLength + IpLength + IntLength;
public byte Id { get; }
public IPAddress LocalIp { get; }
public int LocalPort { get; }
private UdpInfoMessage( byte[] data, byte id, IPAddress localIp, int localPort )
: base( data )
{
Id = id;
LocalIp = localIp;
LocalPort = localPort;
}
public static UdpInfoMessage GetMessage( byte id, IPAddress localIp, int localPort )
{
var data = JoinBytes( Prefix, MessagePrefix, new[] { id }, localIp.GetAddressBytes(), localPort.ToByteArray() );
return new UdpInfoMessage( data, id, localIp, localPort );
}
public static bool TryParse( byte[] data, out UdpInfoMessage message )
{
message = null;
if ( !data.StartsWith( Prefix ) )
return false;
if ( !data.StartsWith( MessagePrefix, Prefix.Length ) )
return false;
if ( data.Length != MessageLength )
return false;
int index = Prefix.Length + MessagePrefix.Length;
byte id = data[index];
index += PeerIdLength;
byte[] localIpBytes = data.Take( index, IpLength );
var localIp = new IPAddress( localIpBytes );
index += IpLength;
byte[] localPortBytes = data.Take( index, IntLength );
int localPort = localPortBytes.GetInt();
message = new UdpInfoMessage( data, id, localIp, localPort );
return true;
}
}
public class PeerAddressMessage : UdpMessage
{
private static readonly byte[] MessagePrefix = { 36, 49 };
private static readonly int MessageLength = Prefix.Length + MessagePrefix.Length + PeerIdLength + ( IpLength + IntLength ) * 2;
public byte Id { get; }
public IPAddress PublicIp { get; }
public int PublicPort { get; }
public IPAddress LocalIp { get; }
public int LocalPort { get; }
private PeerAddressMessage( byte[] data, byte id, IPAddress publicIp, int publicPort, IPAddress localIp, int localPort )
: base( data )
{
Id = id;
PublicIp = publicIp;
PublicPort = publicPort;
LocalIp = localIp;
LocalPort = localPort;
}
public static PeerAddressMessage GetMessage( byte id, IPAddress publicIp, int publicPort, IPAddress localIp, int localPort )
{
var data = JoinBytes( Prefix, MessagePrefix, new[] { id },
publicIp.GetAddressBytes(), publicPort.ToByteArray(),
localIp.GetAddressBytes(), localPort.ToByteArray() );
return new PeerAddressMessage( data, id, publicIp, publicPort, localIp, localPort );
}
public static bool TryParse( byte[] data, out PeerAddressMessage message )
{
message = null;
if ( !data.StartsWith( Prefix ) )
return false;
if ( !data.StartsWith( MessagePrefix, Prefix.Length ) )
return false;
if ( data.Length != MessageLength )
return false;
int index = Prefix.Length + MessagePrefix.Length;
byte id = data[index];
index += PeerIdLength;
byte[] publicIpBytes = data.Take( index, IpLength );
var publicIp = new IPAddress( publicIpBytes );
index += IpLength;
byte[] publicPortBytes = data.Take( index, IntLength );
int publicPort = publicPortBytes.GetInt();
index += IntLength;
byte[] localIpBytes = data.Take( index, IpLength );
var localIp = new IPAddress( localIpBytes );
index += IpLength;
byte[] localPortBytes = data.Take( index, IntLength );
int localPort = localPortBytes.GetInt();
message = new PeerAddressMessage( data, id, publicIp, publicPort, localIp, localPort );
return true;
}
}
public class P2PKeepAliveMessage : UdpMessage
{
private static readonly byte[] MessagePrefix = { 11, 19 };
private static P2PKeepAliveMessage _message;
private P2PKeepAliveMessage( byte[] data )
: base( data )
{
}
public static bool TryParse( byte[] data )
{
if ( !data.StartsWith( Prefix ) )
return false;
if ( !data.StartsWith( MessagePrefix, Prefix.Length ) )
return false;
return true;
}
public static P2PKeepAliveMessage GetMessage()
{
if ( _message == null )
{
var data = JoinBytes( Prefix, MessagePrefix );
_message = new P2PKeepAliveMessage( data );
}
return _message;
}
}
#endregion
}
}

.net remoting problem with chat server

I have a problem with my chat server implementation and I couldn't figure out why it doesn't work as intended.
The client could send messages to the server, but the server only sends the messages to itself instead of the client.
E.g. the client connects to the server, then types "hello" into the chat. The server successfully gets the message but then posts the message to its own console instead of sending it to the connected clients.
Well... maybe I have missed something as I'm very new to .Net remoting. Maybe someone could help me figure out what the problem is. Any help is appreciated!
The code:
I have a small interface for the chat implementation on the server
public class ChatService : MarshalByRefObject, IService
{
private Dictionary<string, IClient> m_ConnectedClients = new Dictionary<string, IClient>();
private static ChatService _Chat;
private ChatService()
{
Console.WriteLine("chat service created");
_Chat = this;
}
public bool Login(IClient user)
{
Console.WriteLine("logging in: " + user.GetIp());
if (!m_ConnectedClients.ContainsKey(user.GetIp()))
{
m_ConnectedClients.Add(user.GetIp(), user);
PostMessage(user.GetIp(), user.GetUserName() + " has entered chat");
return true;
}
return false;
}
public bool Logoff(string ip)
{
Console.WriteLine("logging off: " + ip);
IClient user;
if (m_ConnectedClients.TryGetValue(ip, out user))
{
PostMessage(ip, user + " has left chat");
m_ConnectedClients.Remove(ip);
return true;
}
return false;
}
public bool PostMessage(string ip, string text)
{
Console.WriteLine("posting message: " + text + " to: " + m_ConnectedClients.Values.Count);
foreach (var chatter in m_ConnectedClients.Values)
{
Console.WriteLine(chatter.GetUserName() + " : " + chatter.GetIp());
chatter.SendText(text);
}
return true;
}
}
My Server implements the chatservice as singleton:
RemotingConfiguration.RegisterWellKnownServiceType(typeof(ChatService), "chatservice", WellKnownObjectMode.Singleton);
My client is also simply straight forward:
[Serializable]
public class Chat_Client : IClient
{
private string m_IpAdresse;
private string m_UserName = "Jonny";
private string m_Input;
public Chat_Client(string ip, string username)
{
m_IpAdresse = ip;
m_UserName = username;
}
public bool HandleInput(string input)
{
if (input.Equals("exit"))
{
Client.m_ChatService.Logoff(m_IpAdresse);
return false;
}
m_Input = input;
Thread sendThread = new Thread(new ThreadStart(SendPostMessage));
sendThread.Start();
//Console.WriteLine("post message");
return true;
}
private void SendPostMessage()
{
Client.m_ChatService.PostMessage(m_IpAdresse, m_Input);
Thread thisThread = Thread.CurrentThread;
thisThread.Interrupt();
thisThread.Abort();
}
public void SendText(string text)
{
Console.WriteLine("send text got: " + text);
Console.WriteLine(text);
}
The main client connects to the server via:
public void Connect()
{
try
{
TcpChannel channel = new TcpChannel(0);
ChannelServices.RegisterChannel(channel, false);
m_ChatService = (IService)Activator.GetObject(typeof(IService), "tcp://" + hostname + ":9898/Host/chatservice");
System.Net.IPHostEntry hostInfo = Dns.GetHostEntry(Dns.GetHostName());
m_IpAdresse = hostInfo.AddressList[0].ToString();
Chat_Client client = new Chat_Client(m_IpAdresse, m_UserName);
Console.WriteLine("Response from Server: " + m_ChatService.Login(client));
string input = "";
while (m_Running)
{
input = Console.ReadLine();
m_Running = client.HandleInput(input);
}
}
}

#John: No, I wasn't aware of that. Thanks for the info, I'll look into it.
#Felipe: hostname is the dns name of the server I want to connect to.
I found a workaround to make this work. I added an additional TcpListener to the client to which the server connects when the client logs in. Over this second channel I transmit the chat messages back.
However I couldn't understand why the old solution does not work :<
Thanks for the hints guys.

The best thing to do with .NET remoting is to abandon it for WCF. If you read all the best practices for scalability, the way you end up using it is extremely compatible with the Web Services model, and web services is far easier to work with.
Remoting is technically fascinating and forms the basis of reflection, but falls apart once slow, unreliable connections are involved - and all connections are slow and unreliable compared to in-process messaging.