This is related to c# Sockets.
I'm developping a socket program. But there is one problem in my software.
I cannot connect to computers which are connected to internet via theirs local network. But I can connect to computers that are uses internet alone. Be more descriptive,
Consider that 5 computers connects internet via a modem that uses 1 ip address. When I try to reach one of these computers, API connects to modem via its ip address. But there is no response. Because a modem don't respond a computer request. By the mean, my API must reach a computer not only modem. And and an SocketException is thrown. What can I do about this problem?
The problem you're encountering is caused by NAT. This is used by routers who allow multiple clients to go online through one public IP address. None of the clients behind the router will 'know' or 'see' this, but it limits connectivity.
Clients can initiate a connection to the outside, but the other way around is basically* impossible. Unless you use port forwarding, where one or more ports are forwarded to a client behind the router. This way, connections can be initiated from the outside.
This requires configuration on the client side however, so the preferred way would be to let your clients connect to your server, since that will always be possible (firewalls neglected).
*: There also is a workaround, where you let a client connect to your server, and then pass the connection information to another client, so those clients can communicate with each other. This is called 'nat punching' and is used by torrent clients, for example.
you can try something like this.....
server Side Code
namespace Consoleserver
{
class Program
{
static void Main(string[] args)
{
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp );
try
{
listener.Bind(localEndPoint);
listener.Listen(10);
while (true)
{
Console.WriteLine("Waiting for a connection...");
Socket handler = listener.Accept();
Console.WriteLine("connected");
}
}
catch { Console.WriteLine("error");
}
}
}
Client side code :
namespace consoleclient
{
class Program
{
static void Main(string[] args)
{
try
{
IPHostEntry ipHostInfo = Dns.Resolve("59.178.131.180");
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint remoteEP = new IPEndPoint(ipAddress, 11000);
Socket sender = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
try
{
sender.Connect(remoteEP);
Console.WriteLine("Socket connected <strong class="highlight">to</strong> {0}",
sender.RemoteEndPoint.ToString());
}
catch (ArgumentNullException ane)
{
Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
Console.Read();
}
catch (SocketException se)
{
Console.WriteLine("SocketException : {0}", se.ToString());
Console.Read();
}
catch (Exception e)
{
Console.WriteLine("Unexpected exception : {0}", e.ToString());
Console.Read();
}
}
catch
{ Console.WriteLine("could not <strong class="highlight">connect</strong> A"); }
}
}
}
I hope it will helps you
Related
I have server application .
If I run it at server application just do not communicate with client. I try allow all ports used ports in firewall also whole application, but it did not helped. At localhost it works fine. Working system is correctly updated Win 10. Server is windows server 2012.
public void Listen(object data)
{
// Establish the local endpoint for the socket.
// The DNS name of the computer
// running the listener is "host.contoso.com".
IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(ipAddress.AddressFamily,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and listen for incoming connections.
try
{
listener.Bind(localEndPoint);
listener.Listen(100);
while (true)
{
// Set the event to nonsignaled state.
allDone.Reset();
// Start an asynchronous socket to listen for connections.
Console.WriteLine("Waiting for a connection...at" + localEndPoint.ToString());
listener.BeginAccept(
new AsyncCallback(AcceptCallback),
listener);
// Wait until a connection is made before continuing.
allDone.WaitOne();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
Seems you should be using IPv4 Adresses.
You can use IPAdress's AdressFamily property to get a to valid IPv4 Address ("InterNetwork"). Also check isLoopback().
So, basically
IPAdress myIp = ipHostInfo
.AddressList
.Where( a => a.AddressFamily == AddressFamily.InterNetwork)
.FirstOrDefault(x => !IPAdress.IsLoopback(x));
should give you a good one if one exists.
... or as Damien_The_Unbeliever so greatly reminded me in comment:
Just use IPAdress.Any to listen on any ip.
I'm writing a very simple .NET TCP Server and very simple TCP Client that should both run on the same machine (Window 10 Home PC) and connect each other (for testing purposes only).
In the server I'm waiting for the connection in this way:
public static void StartListening()
{
string hostname = Dns.GetHostName();
IPHostEntry ipHostInfo = Dns.GetHostEntry(hostname);
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, Properties.Settings.Default.Port);
Socket listener = new Socket(
ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
try
{
listener.Bind(localEndPoint);
listener.Listen(Properties.Settings.Default.Port);
while (true)
{
allDone.Reset();
Console.WriteLine("Waiting for a connection...");
listener.BeginAccept(
new AsyncCallback(AcceptCallback),
listener);
allDone.WaitOne();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
public static void AcceptCallback(IAsyncResult ar)
{
allDone.Set();
Socket listener = (Socket)ar.AsyncState;
Socket handler = listener.EndAccept(ar);
StateObject state = new StateObject();
state.workSocket = handler;
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(ReadCallback), state);
var frames = Directory.EnumerateFiles(Properties.Settings.Default.FramesPath);
foreach (string filename in frames)
{
Console.Write("Sending frame: {}...", filename);
SendFile(handler, filename);
Thread.Sleep(Properties.Settings.Default.FrameDelay);
}
}
In the client I'm creating a connection in this way:
private void startClient(string host, int port)
{
IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse(host), port);
ClientTCP = new TcpClient();
ClientTCP.Connect(serverEndPoint);
Reader = new StreamReader(ClientTCP.GetStream());
Listen = true;
listner = Listener();
}
startClient is called in this way.
startClient(txtAddr.Text, (int)int.Parse(txtPort.Text));
When I run the client setting host variable to the current machine name (the same the server retrieve trough Dns.GetHostName() I got this exception:
An invalid ip address was specified.
I tried using 127.0.0.1 and I got:
Connection could not be established. Persistent rejection of the target computer 127.0.0.1:5002
I tried with localhost and I got
An invalid ip address was specified
again. I tried with the IP address assigned to WiFi and I got again
Connection could not be established. Persistent rejection of the target computer 192.168.10.11:5002
I'm sure the computer network works since I'm using it for many other things including connecting to local TCP services and I'm sure both client and server code works since on a different PC I'm able to connect them setting localhost as client host variable value. Why I'm unable to use loopback connections in my code?
Where did I fail?
P.S. I allowed connection to server binary in Windows firewall rules, I also allowed outgoing connection for client binary also.
For anyone willing to inspect the server code here it is:
Server code
You are using the constructor with the "IPEndPoint" parameter. This constructor does not connect to the server automatically and you must call the "Connect" method before using the socket. That is why you are getting the error message "Operation not allowed on unconnected sockets". Also, you have provided a wrong IPEndPoint for client.
Please try this on client:
private void startClient(string host, int port)
{
IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse(host), port);
ClientTCP = new TcpClient();
ClientTCP.Connect(serverEndPoint);
Reader = new StreamReader(ClientTCP.GetStream());
Listen = true;
listner = Listener();
}
You may need some exception handling here, but it should work now.
UPDATE:
The ipHostInfo.AddressList may have more than one addresses and just one of them is what you wanted. It is not necessarily the first one. I specified this manually and it works:
//string hostname = Dns.GetHostName();
//IPHostEntry ipHostInfo = Dns.GetHostEntry("127.0.0.1");
//IPAddress ipAddress = ipHostInfo.AddressList[0];
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 5002);
I have a very strange problem. I'm not able to find the IP Address of the client which my server receives data from. Below is my UDP Listener class.
The IPPacketInformation does not contain the IP. The clientEndPoint which I reference in my EndReceiveMessageFrom does neither.
When I
Console.Writeline(((IPEndPoint)clientEndPoint).Address);
I get the IP Address of the server. I have the server hosted on my own machine so I get my own IP Address. When I try to access clientEndPoint.remoteEndPoint it throws an error because the socket isn't connected (due to being UDP).
So basically, a client from an external IP is able to send data, but I can't answer the client since I'm not able to retrieve it's IP. Any help is appreciated!
public class UdpListener
{
private Socket s;
public byte[] ReceiveBuffer = new byte[2048];
public UdpListener()
{
s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
s.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.PacketInformation, true);
s.Bind(new IPEndPoint(IPAddress.Any, 36200));
}
public void Listen()
{
try
{
EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
s.BeginReceiveMessageFrom(ReceiveBuffer, 0, ReceiveBuffer.Length, SocketFlags.None, ref remoteEndPoint, Recv, s);
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
throw;
}
}
private void Recv(IAsyncResult res)
{
try
{
Socket receiveSocket = (Socket)res.AsyncState;
EndPoint clientEndPoint = new IPEndPoint(IPAddress.Any, 0);
IPPacketInformation packetInfo;
SocketFlags flags = SocketFlags.None;
int udpMessageLength = receiveSocket.EndReceiveMessageFrom(res, ref flags, ref clientEndPoint, out packetInfo);
byte[] udpMessage = new byte[udpMessageLength];
Array.Copy(ReceiveBuffer, udpMessage, udpMessageLength);
Console.WriteLine(
"{0} bytes received from {1} to {2}",
ReceiveBuffer,
clientEndPoint,
packetInfo.Address
);
EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, ((IPEndPoint)receiveSocket.LocalEndPoint).Port);
s.BeginReceiveMessageFrom(ReceiveBuffer, 0, ReceiveBuffer.Length, SocketFlags.None, ref remoteEndPoint, Recv, s);
//Process data
RaiseDataReceived(new ReceivedDataArgs(packetInfo.Address, ((IPEndPoint)clientEndPoint).Port, udpMessage));
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
throw;
}
}
public delegate void DataReceived(ReceivedDataArgs args);
public event DataReceived DataReceivedEvent;
private void RaiseDataReceived(ReceivedDataArgs args)
{
DataReceivedEvent?.Invoke(args);
}
}
I've tried to disable my firewall but that does not help. I've also done Port Forwarding on my router thus I can receive data from external clients.
EDIT to clarify the problem:
Server hosted on my machine behind a NAT with public IP 214.214.214.214.
The client is another machine, behind another NAT with public IP 910.910.910.910.
The client sends a message to the server, server receives it and able to read the content. When server get the IPEndPoint of the client, the displayed IP is 214.214.214.214 (IP of the server, not the Client)
EDIT Maybe I should say that I wasn't able to receive messages from clients on external networks until I ordered a "Dynamic IP" from my ISP. Still can't get the public IP of the source.
EDIT When using Wireshark and sniff a packet sent from external client to my server I can see it's the wrong src IP as well. In the picture below the src IP is my server IP and not the IP of the client that sent the data.
After several days of reading everything I possibly could on routers, network and writing different examples of Receive, ReceiveFrom, ReceiveMessageFrom, BeginReceive, BeginReceiveFrom, BeginReceiveMessageFrom, and ReceiveAsync - I've solved my issue.
I changed my router. I can now get the source IP of the external client using a very old router. The router I was using before was a new Docsis 3.1.
Why it works with an old router, I don't know, but for some reason, the Docsis 3.1 changed the source IP to its own IP before letting the UDP message to my machine.
With using the UdpClient class you can actually retrieve the remote endpoint when receiving a message.
I have used a solution like the following to solve this task:
public void StartServer()
{
var udpServer = new UdpClient(new IPEndPoint(IPAddress.Any, ConnectionInformation.DETECTION_PORT));
udpServer.BeginReceive(new AsyncCallback(detectionCallback), udpServer);
}
private void detectionCallback(IAsyncResult ar)
{
var client = (ar.AsyncState as UdpClient);
if (client.Client == null) return;
var endPoint = new IPEndPoint(IPAddress.Any, ConnectionInformation.DETECTION_PORT);
var bytes = client.EndReceive(ar, ref endPoint);
Debug.WriteLine($"Detection request from: {endPoint}");
}
I'm building a C# chat program, yet I'm facing a problem with outside connection.
When the same computer connects both as server and as client, there seems to be no problem, yet when I try to host the connection on one computer, the other can't connect as a client.
here's the relevant code:
class Server:
public void Connect(string ipAddr, string port)
{
server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipLocal = new IPEndPoint(IPAddress.Any, Convert.ToInt32(port));
server.Bind(ipLocal);//bind to the local IP Address...
server.Listen(5);//start listening...
// create the call back for any client connections...
server.BeginAccept(new AsyncCallback(OnClientConnect), null);
}
public void Disconnect()
{
server.Close();
server = null;
tempSocket = null;
}
public void OnClientConnect(IAsyncResult asyn)
{
try
{
if (server != null)
{
tempSocket = server.EndAccept(asyn);
WaitForData(tempSocket);
server.BeginAccept(new AsyncCallback(OnClientConnect), null);
}
}
catch (ObjectDisposedException)
{
Debugger.Log(0, "1", "OnClientConnect: Socket has been closed.");
}
catch (Exception e)
{
MessageBox.Show(e.Message, "OnClientConnect Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
Client class:
public void Connect(string ipAddr, string port)
{
client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipe = new IPEndPoint(IPAddress.Parse(ipAddr), Convert.ToInt32(port));
client.Connect(ipe);
clientListener = new Thread(OnDataReceived);
isEndClientListener = false;
clientListener.Start();
}
I have no idea what's wrong here. Hope you can tell me what's wrong.
Your issue is probably not code related. In order for other people outside your network to conenect to you, you need to port forward the port that you are connecting through on your router. You can find many tutorials here. You may also check to see if your connection is open through this tool.
From Wikipedia:
Port forwarding allows remote computers (for example, computers on the Internet) to connect to a specific computer or service within a private local-area network (LAN).
You must allow connections through your router to be able to connect to your chat server.
You need to give your computer a public IP address (maybe your router has this option) or implement port forwarding on your router.
A Public IP address would be the one of your router. Check out this site to find out your public IP whatismyipaddress.com. Your router can or cannot support the option to give its public IP address to your computer, however, your router should be able to do port forwarding. (Forwarding the data from a specific port to a specific computer, so when someone connects to your public IP. For example 93.93.93.93:3333 will be forwarded to your PC.)
I am using this server example from MSND: http://msdn.microsoft.com/en-us/library/fx6588te.aspx
and from some reason my server refuse to connect at this function at _listener.Bind(localEndPoint); with error Only one usage of each socket address (protocol/network address/port) is normally permitted
Until a few minutes ago I had no problems Sarver connect without problems and suddenly it happens
public static void StartListening(IPAddress ipAddress, int port)
{
_isServerRunning = true;
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// The DNS name of the computer
// running the listener is "host.contoso.com".
//IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
//IPAddress ipAddress = IPAddress.Parse("192.168.0.100"); //ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, port);
// Create a TCP/IP socket.
_listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and listen for incoming connections.
try
{
_listener.Bind(localEndPoint);
_listener.Listen(100);
while (true)
{
// Set the event to nonsignaled state.
allDone.Reset();
// Start an asynchronous socket to listen for connections.
Console.WriteLine("Waiting for a connection...");
_listener.BeginAccept(
new AsyncCallback(AcceptCallback),
_listener);
// Wait until a connection is made before continuing.
allDone.WaitOne();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
//Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
What does this error means ?
It most likely means that the local port is still reserved. This can be idther because another process is still runnoing and holding the sockewt open, or because the timeout period defined by th dSO_LINGER socket option is not timed out. I'm not familiar with c# but there should be a way to set th elinger timeout.
You can tell the current status of the socket by using the netstat command.
I think you can find some solutions here http://blogs.msdn.com/b/dgorti/archive/2005/09/18/470766.aspx