Develop Reference

Send data to specific client from another client with a server in middle[C#]

I have searched everywhere but couldn't find as they are all answering to send message to all clients. What I want to achieve is multiple clients request to server to request data from another client and other client sends data to server telling it that data is for requesting client and so. I don't know how to achieve this. I'm new to this.
What I want to achieve:
I have tried with Data sending client to listen and requesting client to connect to it and transfer data. I have achieved this on local network but to make it work online it needs port forwarding and my user will be a lot of different people so port forwarding is not possible for every user. So I can rent a server which will act as a center of transfer. I programmed a test server in console which will listen to a server IP:port X and accept new clients and their data on port X and forward it to server IP:port Y but what this does is send data to all clients on port Y. I cannot send it to clients public ip address directly for obvious reasons. I understand that all the requesting clients are connected to port Y but I cannot create and assign new ports to all the clients interacting. So I want a way to determine how to request and receive the data without the need of assigning or creating new ports to different clients on same server.
What I have tried:
Server code
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace Test___server
{
class server
{
public static string serverIP = "192.168.0.102";
static void Main(string[] args)
{
Thread listenSendingThread = new Thread(listenSending);
listenSendingThread.IsBackground = true;
listenSendingThread.Start();
Thread listenReceivingThread = new Thread(listenReceiving);
listenReceivingThread.IsBackground = true;
listenReceivingThread.Start();
Console.ReadKey();
}
public static List<TcpClient> listSending = new List<TcpClient>();
public static List<TcpClient> listReceiving = new List<TcpClient>();
public static TcpClient clientSending = null;
private static void listenSending()
{
TcpListener listenerSending = new TcpListener(IPAddress.Parse(serverIP), 5319);
listenerSending.Start();
Console.WriteLine("Server listening to " + serverIP + ":5319");
while(true)
{
clientSending = listenerSending.AcceptTcpClient();
listSending.Add(clientSending);
Console.WriteLine("Sender connection received from " + clientSending.Client.RemoteEndPoint);
}
}
private static void send()
{
StreamWriter sw = new StreamWriter(clientSending.GetStream());
sw.WriteLine(message);
sw.Flush();
Console.WriteLine("Message sent!");
}
public static string message = string.Empty;
private static void listenReceiving()
{
TcpListener listener = new TcpListener(IPAddress.Parse(serverIP), 0045);
listener.Start();
Console.WriteLine("Server listening to " + serverIP + ":0045");
while (true)
{
TcpClient client = listener.AcceptTcpClient();
listReceiving.Add(client);
Console.WriteLine("Receiver connection received from " + client.Client.RemoteEndPoint);
StreamReader sr = new StreamReader(client.GetStream());
message = sr.ReadLine();
send();
}
}
}
}
Requesting client code
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Test____admin
{
class admin
{
static void Main(string[] args)
{
Console.WriteLine("Begin");
string serverIP = "192.168.0.102";
System.Net.Sockets.TcpClient clientSocket = new System.Net.Sockets.TcpClient();
clientSocket.Connect(serverIP, );
Console.WriteLine("Connected");
while (true)
{
Console.WriteLine("Reading");
StreamReader sr = new StreamReader(clientSocket.GetStream());
Console.WriteLine("Message: " + sr.ReadLine());
}
}
}
}
Request satisfying client code
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
namespace Test___client
{
class client
{
public static string serverIP = "192.168.0.102";
static void Main(string[] args)
{
clientConnect();
}
private static void clientConnect()
{
try
{
TcpClient client = new TcpClient(serverIP, 0045);
StreamWriter sw = new StreamWriter(client.GetStream());
sw.WriteLine("Karan!");
sw.Flush();
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
}
}

You are using a very low-level API, and doing it the right way is challenging. Instead, try YARP as a reverse proxy. The requesting client should notify the reverse proxy about the desired destination client. One option is sending the destination client name in the request header. You will also need to split a single server request into multiple client requests, then merge their responses into a single one. You can achieve it by implementing Transphorms.
I'm not sure this approach applies to your situation because clients should implement server API using REST, Grpc or any other supported technology.

Sending udp packets between computers in C#

I am trying to send an udp packet from one computer to another in a local network. One computer is running Windows 10, other Ubuntu 18.04.
The code I have so far is this:
Server:
using System;
using System.Net.Sockets;
using System.Net;
namespace udpTest
{
class Program
{
static void Main(string[] args)
{
string hostName = Dns.GetHostName();
string ip = Dns.GetHostEntry(hostName).AddressList[0].ToString();
IPAddress ipadd = IPAddress.Parse(ip);
var serverEndPoint = new IPEndPoint(ipadd, 20020);
var udp = new UdpClient(ipadd.ToString(), 20020);
while (true) {
var recvData = udp.ReceiveAsync().Result;
System.Console.WriteLine($"received: {recvData.Buffer}");
}
}
}
}
Client:
using System;
using System.Net.Sockets;
using System.Net;
namespace C_
{
class Program
{
static void Main(string[] args)
{
var udp = new UdpClient();
var bytes = BitConverter.GetBytes(420);
var i = udp.SendAsync(bytes, bytes.Length, "fe80::7077:8d67:4984:c9bc%43", 20020 ).Result;
System.Console.WriteLine($"sent: {i}");
}
}
}
(I changed the ipv6 address a bit but format is exactly the same).
I get no errors when sending or anything, it just goes through but the server does not catch it. I have no idea what I am doing wrong. So any pointers would be most appreciated.
Edit: updated code works within lan, but not outside LAN.
Client:
static void Main(string[] args)
{
var udp = new UdpClient("192.168.1.117", 20020);
var bytes = BitConverter.GetBytes(420);
var i = udp.SendAsync(bytes, bytes.Length).Result;
System.Console.WriteLine($"sent: {i}");
}
Server:
static void Main(string[] args)
{
var serverEndPoint = new IPEndPoint(IPAddress.Any, 20020);
var udp = new UdpClient(serverEndPoint);
while (true) {
var recvData = udp.ReceiveAsync().Result;
System.Console.WriteLine($"received: {recvData.Buffer}");
}
}

first try IPAddress.Any since using the first IP address from Dns.GetHostEntry(hostName).AddressList[0].ToString(); is not guaranteed to be the IPv6 address you are using, specially if the computer has more than one network adapter.
Second is using the serverEndPoint you created for the UdpClient constructor
// Use IPAddress.Any
IPAddress ipadd = IPAddress.Any;
var serverEndPoint = new IPEndPoint(ipadd, 20020);
// Use the serverEndPoint for the UP
var udp = new UdpClient(serverEndPoint);
Third, check the server's firewall settings and make sure you allow incoming UDP messages on port 20020 (by default on both Windows and Ubuntu it is not allowed). And check the client firewall settings and make sure outgoing UDP messages on port 20020 are allowed (by default on both Windows and Ubuntu it is allowed).

How can i scan and list all connected devices to my network wireless, i'm getting exception?

My pc is connected to the router of the network i want to scan but the not wireless the pc is connected with a cable to the router.
But my android device is connected to the network wireless.
So in logic in this case the results in the list should be my pc and my android device.
This is what i'm using now managed wifi api:
managed wifi api
This is my code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using NativeWifi;
namespace ScanWifi
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
WlanClient client = new WlanClient();
try
{
foreach (WlanClient.WlanInterface wlanIface in client.Interfaces)
{
Wlan.WlanBssEntry[] wlanBssEntries = wlanIface.GetNetworkBssList();
foreach (Wlan.WlanBssEntry network in wlanBssEntries)
{
int rss = network.rssi;
byte[] macAddr = network.dot11Bssid;
string tMac = "";
for (int i = 0; i < macAddr.Length; i++)
{
tMac += macAddr[i].ToString("x2").PadLeft(2, '0').ToUpper();
}
listView1.Items.Add("Found network with SSID {0}." + System.Text.ASCIIEncoding.ASCII.GetString(network.dot11Ssid.SSID).ToString());
listView1.Items.Add("Signal: {0}%."+ network.linkQuality);
listView1.Items.Add("BSS Type: {0}."+ network.dot11BssType);
listView1.Items.Add("MAC: {0}.", tMac);
listView1.Items.Add("RSSID:{0}", rss.ToString());
}
Console.ReadLine();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void Form1_Load(object sender, EventArgs e)
{
}
}
}
When running the program i'm exception on WlanApi.cs on the line:
Wlan.ThrowIfError(
Wlan.WlanOpenHandle(Wlan.WLAN_CLIENT_VERSION_XP_SP2, IntPtr.Zero, out negotiatedVersion, out clientHandle));
System.ComponentModel.Win32Exception' occurred in ManagedWifi.dll
The service has not been started

For Windows 10, the service "WLAN AutoConfig" must be started for WlanClient to work. This service should be started automatically on a computer which has a WiFi adapter present. On a computer such as a desktop which does not have a WiFi adapter, the service startup type is probably Manual and not started; you can start it anyway and WlanClient should no longer throw any exceptions, but without a WiFi adapter, it won't see any interfaces, so you won't be able to get a list of networks.

According to the documentation of the [WlanOpenHandle ][1] function, the problem is that the Wireless Zero Configuration (WZC) service is not started on your machine:
WlanOpenHandle will return an error message if the Wireless Zero Configuration (WZC) service has not been started or if the WZC service is not responsive.
However, depending on your platform, it might also might be the case that you are simply passing the wrong parameters to the WlanOpenHandle function. Have you tried passing Wlan.WLAN_CLIENT_VERSION_LONGHORN as the first parameter?

Trying to create a chat application in Visual Studio 2010

I am a beginner in networking but I have to start with something, so I decided to create a chat app in visual studio 2010 using C# language (winforms).
I googled a lot about that and I've found almost exactly what I needed.
I found the following code samples (in C# - console):
http://msdn.microsoft.com/en-us/library/system.net.sockets.tcpclient.aspx
http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener(v=VS.71).aspx
I want to create that application using TCP protocol (I don't know if there are easier ways to do that, but I understood the basics of TCP when I tried to create that chat in C#.
When I executed the code samples in the links above, they worked! So I tried to adapt those samples at my chat application.
My chat application consists actually of two apps: a server and a client. Both of them have the same GUI (two text boxes, a button and two labels for displaying whether the client is connected to the server).
textBox1 on the server/client app is the one that display the message sent by the client/server app.
In the textBox2 on the server/client app the user types a message and then presses the button to send the message to the client/server app.
Let me show you what I've tried until now:
This is the server application code.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
namespace Server_TCP_WINFORMS
{
public partial class Form1 : Form
{
//Int32 port = 13000;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
TcpListener server = new TcpListener(IPAddress.Parse("127.0.0.1"), 13000);
public Form1()
{
InitializeComponent();
server.Start();
}
byte[] bytes = new byte[256];
String data = null;
TcpClient client = new TcpClient();
bool sw = true;
int data_at_byte_level = 0;
private void Form1_Load(object sender, EventArgs e)
{
try
{
label2.Text = "Waiting for an incoming connection...";
if (!server.Pending())
{
label2.Text = "For moment, there are no connections requests!";
}
else
{
client = server.AcceptTcpClient();
label2.Text = "Connected!";
sw = false;
}
}
catch (SocketException xyz)
{
MessageBox.Show("Exception occured!");
}
if (sw == false)
{
NetworkStream stream = client.GetStream();
while ((data_at_byte_level = stream.Read(bytes, 0, bytes.Length)) != 0)
{
data = System.Text.Encoding.ASCII.GetString(bytes);
textBox1.Text += data;
data = null;
bytes = null;
}
}
}
private void button1_Click(object sender, EventArgs e)
{
String dataT;
if (textBox2.Text!=null && sw == false)
{
NetworkStream stream = client.GetStream();
dataT = textBox2.Text;
byte[] msg = System.Text.Encoding.ASCII.GetBytes(dataT);
stream.Write(msg, 0, msg.Length);
}
}
}
}
And this is the client application code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Net;
namespace Client_TCP_WINFORMS
{
public partial class Form1 : Form
{
TcpClient client = new TcpClient("127.0.0.1", 13000);
public Form1()
{
InitializeComponent();
label2.Text = "Conected to the server!";
}
private void button1_Click(object sender, EventArgs e)
{
NetworkStream stream = client.GetStream();
if (textBox2.Text != null)
{
String data_str = textBox2.Text;
Byte[] data_byte = System.Text.Encoding.ASCII.GetBytes(data_str);
stream.Write(data_byte, 0, data_byte.Length);
}
}
private void Form1_Load(object sender, EventArgs e)
{
Byte[] data_byte = new Byte[290];
int bytes;
string Data;
NetworkStream stream = client.GetStream();
bytes = stream.Read(data_byte, 0, data_byte.Length);
Data = System.Text.Encoding.ASCII.GetString(data_byte, 0, bytes);
textBox1.Text += Data;
}
}
}
I want that those two apps to behave in the following way: I start the server application then I start the client application. When both of them are open, I want them to be already connected (because it's simpler that way, I think).
Then, I want that both of them to be receptive which means that when the server (for example) sends a message to the client, the latter one should receive the message and display it. If the server send another message, the client should receive and display it too.
If the user (of the client or the user of the server) presses the send button, the application should send the message from the textBox2 to the other application. How can I do those things in windows forms?
I see in the code samples in console that there is a main loop where the server reads the message from the client. But what if the server wants to send a message too? If the send button is pressed, the event for the button_pressed occurs and then it sends the message, but when it finished sending the message, it goes back to the main loop?
Please excuse my english. I am not a native speaker.
Thank you respectfully.

"When both of them are open, I want them to be already connected (because it's simpler that way, I think)."
For this, you need to use UDP(User Datagram Protocol) rather than TCP

SharpSVN connection rate limit to localhost?

We use SharpSVN to programmatically access SVN repositories. Now we have the problem that the access to local repositories via svn:// or http:// urls is very slow - every access needs at least one second, and our app needs to fetch a bunch of properties and directory listings.
We could reproduce the problem on two different machines, both are Windows 7 32 bit and are in the same domain. The SVN servers are VisualSVN 2.1.9 for http:// urls and the CollabNet 1.6.17 for svn:// urls. It appears for connections via "localhost" and via the host name. It appears in our C# application, as well as a small testbed app using IronPython and when calling the SharpSvn svn.exe command.
This problem does not happen when accessing when accessing remote repositories (Both a linux and a windows XP server) - here, each access is between 0.01 and 0.08 secs, which is expected due to network latency. The Problem also does not happen when acessing the local repositories via file:// urls or when accessing the repositories via "native" svn command line tools from CollabNet.
Now my question is: Has Windows 7 or .NET or SharpSVN some built-in limit which only applies to localhost connections?
(Addition: I now found out that this limit also applies when connecting via a small C# test program using System.Net.Sockets.TcpClient:
Server:
using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
namespace TcpSpeedServer
{
class Program
{
public static void Main()
{
Int32 port = 47011;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
var server = new TcpListener(localAddr, port);
server.Start();
Console.WriteLine("Listening on {0} : {1}", localAddr, port);
ulong count = 0;
// Enter the listening loop.
while(true)
{
using (var client = server.AcceptTcpClient()) {
Console.WriteLine("Connected: {0} {1}!", count, client.Client.RemoteEndPoint);
count += 1;
using (var stream = client.GetStream()) {
using (StreamWriter writer = new StreamWriter(stream))
using (StreamReader reader = new StreamReader(stream))
{
string query = reader.ReadLine();
writer.WriteLine("GET / HTTP/1.0");
writer.WriteLine();
writer.Flush();
}
}
}
}
}
}
}
Client:
using System;
using System.Collections.Generic;
using System.IO;
using System.Net.Sockets;
using System.Threading;
namespace TcpSpeedTest
{
class Program
{
const bool ASYNC = false;
static DateTime s_now;
public static void Main(string[] args)
{
var liste = new List<object>();
s_now = DateTime.Now;
for (int i=0; i < 100; i += 1) {
if (ASYNC)
ThreadPool.QueueUserWorkItem(connect, i);
else
connect(i);
}
Console.WriteLine("outer: " + (DateTime.Now - s_now));
Console.ReadLine();
}
private static void connect(object i)
{
DateTime now = DateTime.Now;
using (TcpClient client = new TcpClient("localhost", 47011))
{
var stream = client.GetStream();
using (StreamWriter writer = new StreamWriter(stream))
using (StreamReader reader = new StreamReader(stream))
{
writer.WriteLine("GET / HTTP/1.0");
writer.WriteLine();
writer.Flush();
string result = reader.ReadLine();
}
}
Console.WriteLine(string.Format("inner: {0} - {1} - {2}", i, DateTime.Now - now, DateTime.Now - s_now));
}
}
}
So this problem seems not to be subversion specific.)
Addition2: When running the client under Mono 2.10 for windows, the problem does not appear. So it seems to be specific to .NET framework.
Addition3: It seems to be an IPv6 related problem. The server only listens on IPv4, but the hostname also resolves to IPv6. Now it seems that the OS code internally tries the IPv6 connection, and after getting the connection reset, waits 1 sec before falling back to IPv4. And this game is repeated for every single connection attempt. http://msdn.microsoft.com/en-us/library/115ytk56.aspx documents that for TcpClient (thanks to Andreas Johansson from the MSDN forums for the hint!), and it seems that the APR used by Apache internally uses a similar mechanism.

Addition 3 is also the solution to your problem. To fix this, either make DNS/hosts file only resolve to an IPv4 address, or make the IPv6 server(s) work.
You can enter in C:\Windows\System32\drivers\etc\hosts something like:
127.0.0.1 localhost-ipv4
And then use that name to connect.
You can also make svnserve listen to IPv6 addresses. A quick search for svnserve options [revealed][1] that it defaults to IPv6, so in its startup parameters is probably a --listen-host. Try removing that, or when it's not present forcing it to run at IPv6.
The same can be done for the Apache webserver:
Listen 0.0.0.0:80
Listen [::]:80