Develop Reference

C# Receive TCP messages while sending

I'm having an issue with making an async tcp listener in C# (.NET 6). Basically, I have two computers (one with an IP of 172.22.167.159 and the other with an IP of 172.22.160.1). On the computer with an IP of .160.1, I want to be able to send text to the computer with IP .167.159 while being able to receive messages from it too. Currently, I'm able to send messages to .167.159, but when I try to set up an async function to receive messages (so I can still send while receiving). However, I'm unable to make it work (when I run it, the whole program just doesn't do anything). Below is my code, thanks for the help:
using System.Net;
using System.Net.Sockets;
using System.Text;
namespace TcpTest
{
public class Program
{
public static void Main(string[] args)
{
// create socket to .167.159
Socket soc = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPAddress ipAdd = IPAddress.Parse("172.22.167.159");
IPEndPoint remoteEP = new IPEndPoint(ipAdd, 44444);
soc.Connect(remoteEP);
Listen(); // listen for text from .167.159 async so input isn't blocked, allowing me to still send text
// send data to .167.159
while (true)
{
byte[] byData = Encoding.ASCII.GetBytes($"{Console.ReadLine()}\n");
soc.Send(byData);
}
}
private static async void Listen()
{
try
{
int port = 44444;
IPAddress ipAddress = IPAddress.Parse("172.22.160.1");
TcpListener server = new TcpListener(ipAddress, port);
server.Start();
byte[] bytes = new byte[256];
string? data = null;
while (true)
{
TcpClient client = server.AcceptTcpClient();
data = null;
NetworkStream stream = client.GetStream();
int i;
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine($"Received: {data}");
data = data.ToUpper();
byte[] msg = System.Text.Encoding.ASCII.GetBytes(data);
stream.Write(msg, 0, msg.Length);
Console.WriteLine($"Sent: {data}");
}
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
}
}

Send and receive data in c# network programming winform

I have a small server that is received and sends the message back to the client.
this is the client-side
when I open the client it will connect to server through Connect()
public Form1()
{
InitializeComponent();
Connect();
CheckForIllegalCrossThreadCalls = false;
}
this is my connect
void Connect()
{
ipep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9999);
server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
try
{
server.Connect(ipep);
}
catch (SocketException e)
{
MessageBox.Show(Convert.ToString(e));
}
Thread listen = new Thread(Receive);
listen.IsBackground = true; ;
listen.Start();
}
and I have a receive like this
void Receive()
{
datarec = new byte[1024];
try
{
while (true)
{
string StringData;
rec = server.Receive(datarec);
StringData = Encoding.ASCII.GetString(data, 0, rec);
txtShow.Text = StringData;
}
}
catch
{
Close();
}
}
and I send data through a button have Send method
void Send(string s)
{
data = new byte[1024];
data = Encoding.ASCII.GetBytes(s);
server.Send(data, data.Length, SocketFlags.None);
}
Send button
private void button1_Click(object sender, EventArgs e)
{
string s = txtText.Text;
Send(s);
}
this is the server-side
I have a thread server
public static void Process(Socket client)
{
byte[] data = new byte[1024];
int recv;
string dataInput;
IPEndPoint clientep = (IPEndPoint)client.RemoteEndPoint;
Console.WriteLine("Connected with {0} at port {1}", clientep.Address, clientep.Port);
while (true)
{
try
{
recv = client.Receive(data);
dataInput = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine(dataInput);
client.Send(data);
}
catch (SocketException e)
{
Console.WriteLine(e);
}
}
}
this is the server main
public static void Main()
{
byte[] rec = new byte[1024];
IPEndPoint ipep = new IPEndPoint(IPAddress.Any, 9999);
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
server.Bind(ipep);
server.Listen(10);
Console.WriteLine("Waiting for client...");
Console.WriteLine("LOG CHAT");
while (true)
{
Socket client = server.Accept();
Core core = new Core();
Thread t = new Thread(() => Core.Process(client));
t.Start();
}
}
the server receive message but when it sends a message back it has an error "An established connection was aborted by the software in your host machine"
Can you guys tell me where I was wrong and how can I fix it?

When you call client.Send(data) in your server code, you will send the whole 1024 byte buffer back to the client, not just the data received.
Encoding.ASCII.GetString in the client could fail when processing this garbage and the exception will close the connection.
Try to replace client.Send(data) by client.Send(data, recv, SocketFlags.None).
Also, you should not update UI controls directly from a background thread, Use Control.Invoke for this. Failing to do so will also throw an exception and close the connection.

TcpListener Client stays connected sending multiple messages but server only receives or processes the first message

I am setting up a server to read some network clients using TcpListener. The Client sends some data I verify that data and send a response to that data, the client stays connected and sends a second response and I verify that data and send a response back, its like logging in to the server twice. The first login get sent back to the client just fine but the second time the client responds the server does not show that it received anymore data from the client.
I have tested it by setting up a dummy client (the real client is Cell phone based ODB2). With the dummy client set up I did verify that the first handshake happens but the when the client sends the second set of text it does not show up on the server.
class Program
{
static private TcpListener listener = null;
static private TcpClient client = null;
static private NetworkStream stream = null;
static private int iCount = 0;
static Int32 port = 8090;
static IPAddress localAddr = IPAddress.Parse("192.168.1.17");
static void Main(string[] args)
{
listener = new TcpListener(localAddr, port);
listener.Start();
while (true)
{
try
{
client = listener.AcceptTcpClient();
ThreadPool.QueueUserWorkItem(ThreadProc, client);
}
catch (IOException ioex)
{
RestartStream();
}
}
}
private static void ThreadProc(object obj)
{
var client = (TcpClient)obj;
Byte[] bytes = new Byte[client.ReceiveBufferSize];
stream = client.GetStream();
try
{
int bytesRead = stream.Read(bytes, 0, (int)client.ReceiveBufferSize);
string returndata = Encoding.ASCII.GetString(bytes, 0, bytesRead).Replace("-", "");
byte[] sendBytes;
if (returndata.ToLower().StartsWith("7e") && returndata.ToLower().EndsWith("7e"))
{
//… do stuff with the data and send it back to the client
sendBytes = Encoding.Default.GetBytes(login1);
stream.Write(sendBytes, 0, sendBytes.Length);
stream.Flush();
}
else
{
SaveStream(returndata);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
Test Client Code:
//---data to send to the server---
string textToSend = "7E010000360141850000080000000000000000000000000000000000000000000000000000000000000035303030303038003131313131313131313131313131313131F67E";
//---create a TCPClient object at the IP and port no.---
TcpClient client = new TcpClient(SERVER_IP, PORT_NO);
NetworkStream nwStream = client.GetStream();
byte[] bytesToSend = ASCIIEncoding.ASCII.GetBytes(textToSend);
//---send the text---
Console.WriteLine("Sending : " + textToSend);
nwStream.Write(bytesToSend, 0, bytesToSend.Length);
//---read back the text---
byte[] bytesToRead = new byte[client.ReceiveBufferSize];
int bytesRead = nwStream.Read(bytesToRead, 0, client.ReceiveBufferSize);
Console.WriteLine("Received : " + Encoding.ASCII.GetString(bytesToRead, 0, bytesRead));
string Text2 = "7E0100003601418535303030303038003131313131313131313131313131313131F67E";
Console.WriteLine("Sending : " + Text2);
byte[] bytesToSend2 = ASCIIEncoding.ASCII.GetBytes(Text2);
nwStream.Write(bytesToSend2, 0, bytesToSend2.Length);
client.Close();
Console.ReadLine();
What I need to happen is my understanding is the client stays connected the whole time and send data over and over, my system seems to accept it once and then stops receiving it, I need it to continue to receive the client data and process it.

Ok so I figured it out, there should be a second while loop in side the thread.
static void Main(string[] args)
{
listener = new TcpListener(localAddr, port);
var clientSocket = default(TcpClient);
listener.Start();
var counter = 0;
while (true)
{
clientSocket = listener.AcceptTcpClient();
var client = new ConnectedDevice();
client.startClient(clientSocket, counter.ToString(), sqlConnString);
}
}
ConnectedDevice class:
class ConnectedDevice
{
private TcpClient _clientSocket;
private string _clientNumber;
private string _sqlConnString;
public void startClient(TcpClient clientSocket, string clientNumber, string sqlConnString)
{
_clientSocket = clientSocket;
_clientNumber = clientNumber;
_sqlConnString = sqlConnString;
var ctThread = new Thread(ProcessClient);
ctThread.Start();
}
private void ProcessClient()
{
while (_clientSocket.Connected)
{
try
{
Byte[] bytes = new Byte[_clientSocket.ReceiveBufferSize];
var networkStream = _clientSocket.GetStream();
networkStream.ReadTimeout = 10000;
int i;
while ((i = networkStream.Read(bytes, 0, bytes.Length)) != 0)
{
var data = System.Text.Encoding.ASCII.GetString(bytes, 0, i).Replace("-", "");
byte[] sendBytes;
Console.WriteLine(data);
string sLogin1 = "7E81000013014185000008000000000054523230313731303138303930303137497E";
sendBytes = Encoding.ASCII.GetBytes(sLogin1);
networkStream.Write(sendBytes, 0, sendBytes.Length);
networkStream.Flush();
}
}
catch (Exception ex)
{
}
}
}
}

TCP port reading in C#

I have an application running at remote server which writes data (string) to its local port, I want to read this systems port by another C# application running at some other system, When i connect to this port of the remote machine I get an error that the target machine actively refused the connection.
Any suggestion will be appreciated.
I have tried this code:
Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
var ipaddress = IPAddress.Parse("192.168.1.12");
IPAddress add = new IPAddress(ipaddress.GetAddressBytes());
EndPoint ep = new IPEndPoint(add, 7862);
sock.Connect(ep);
if (sock.Connected)
{
byte[] bytes = new byte[256];
int i = sock.Receive(bytes);
Console.WriteLine(Encoding.UTF8.GetString(bytes));
}
Here 192.168.1.12 is the IP address of the remote system, where an application is writing string continuously to port 7862. I need to read the value from that port via a C# application

I had written a program like that while ago... i copy paste it as it is, dont forget to allow "port" to the firewall and NAT so that the packet actually gets through
class Transmitter
{
public Boolean Transmit(String ip ,String port, String data){
TcpClient client = new TcpClient();
int _port = 0;
int.TryParse(port, out _port);
IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse(ip), _port);
client.Connect(serverEndPoint);
NetworkStream clientStream = client.GetStream();
ASCIIEncoding encoder = new ASCIIEncoding();
byte[] buffer = encoder.GetBytes(data);
clientStream.Write(buffer, 0, buffer.Length);
clientStream.Flush();
return true;
}
}
class Listener
{
private TcpListener tcpListener;
private Thread listenThread;
// Set the TcpListener on port 13000.
Int32 port = 8081;
IPAddress localAddr = IPAddress.Parse("192.168.1.3");
Byte[] bytes = new Byte[256];
MainWindow mainwind = null;
public void Server(MainWindow wind)
{
mainwind = wind;
this.tcpListener = new TcpListener(IPAddress.Any, port);
this.listenThread = new Thread(new ThreadStart(ListenForClients));
this.listenThread.Start();
}
private void ListenForClients()
{
this.tcpListener.Start();
while (true)
{
//blocks until a client has connected to the server
TcpClient client = this.tcpListener.AcceptTcpClient();
//create a thread to handle communication
//with connected client
Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));
clientThread.Start(client);
}
}
private void HandleClientComm(object client)
{
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
byte[] message = new byte[4096];
int bytesRead;
while (true)
{
bytesRead = 0;
try
{
//blocks until a client sends a message
bytesRead = clientStream.Read(message, 0, 4096);
}
catch
{
//a socket error has occured
// System.Windows.MessageBox.Show("socket");
break;
}
if (bytesRead == 0)
{
//the client has disconnected from the server
// System.Windows.MessageBox.Show("disc");
break;
}
//message has successfully been received
ASCIIEncoding encoder = new ASCIIEncoding();
mainwind.setText(encoder.GetString(message, 0, bytesRead));
//System.Windows.MessageBox.Show(encoder.GetString(message, 0, bytesRead));
// System.Diagnostics.Debug.WriteLine(encoder.GetString(message, 0, bytesRead));
}
tcpClient.Close();
}
}

TCP/UDP Socket server on WAN

I have written a socket server in c# that will be used as the basic design for a small game project I am part of. The socket server works fine on lan. I able to communicate completely fine between the server and the client. However on the WAN the server receives all the correct messages from the client, but the client receives no messages from the server. Both the client and the server are behind a router but only the server's router has the ports forwarded. When the client connects to the server I get the IP address of the connection. Because the client is behind a NAT, is there more information from the sender that I need to collect? I assume the client could set up port forwarding but that would be VERY counter-productive to the game. Any help I can get is appreciated. If you need code let me know. Thanks in advance.
Used to make the TCP connection from the client
public string ConnectionAttempt(string ServeIP, string PlayUsername)
{
username = PlayUsername;
try
{
connectionClient = new TcpClient(ServeIP,TCP_PORT_NUMBER);
connectionClient.GetStream().BeginRead(readbuffer, 0, READ_BUFFER_SIZE, new AsyncCallback(DoRead), null);
Login(username);
ipAddress = IPAddress.Parse(((IPEndPoint)connectionClient.Client.RemoteEndPoint).Address.ToString());
servIP = new IPEndPoint(ipAddress,65002);
listenUDP = new IPEndPoint(ipAddress, 0);
UDPListenerThread = new Thread(receiveUDP);
UDPListenerThread.IsBackground = true;
UDPListenerThread.Start();
return "Connection Succeeded";
}
catch(Exception ex) {
return (ex.Message.ToString() + "Connection Failed");
}
}
Listens for a UDP message on a thread.
private void receiveUDP()
{
System.Net.IPEndPoint test = new System.Net.IPEndPoint(System.Net.IPAddress.Any, 0);
System.Net.EndPoint serverIP = (System.Net.EndPoint)test;
server.Bind(serverIP);
EndPoint RemoteServ = (EndPoint)servIP;
while (true)
{
byte[] content = new byte[1024];
int data = server.ReceiveFrom(content, ref RemoteServ);
string message = Encoding.ASCII.GetString(content);
result = message;
ProcessCommands(message);
}
}
Server TCP connection Listener:
private void ConnectionListen()
{
try
{
listener = new TcpListener(System.Net.IPAddress.Any, PORT_NUM);
listener.Start();
do
{
UserConnection client = new UserConnection(listener.AcceptTcpClient());
client.LineRecieved += new LineRecieve(OnLineRecieved);
UpdateStatus("Someone is attempting a login");
} while (true);
}
catch
{
}
}
Server UDP Listener:
private void receiveUDP()
{
System.Net.IPEndPoint test = new System.Net.IPEndPoint(System.Net.IPAddress.Any, UDP_PORT);
System.Net.EndPoint serverIP = (System.Net.EndPoint)test;
trans.Bind(serverIP);
System.Net.IPEndPoint ipep = new System.Net.IPEndPoint(System.Net.IPAddress.Any, 0);
System.Net.EndPoint Remote = (System.Net.EndPoint)ipep;
while (true)
{
byte[] content = new byte[1024];
int recv = trans.ReceiveFrom(content,ref Remote);
string message = Encoding.ASCII.GetString(content);
string[] data = message.Split((char)124);
//UpdateStatus(data[0] + data[1]);
UserConnection sender = (UserConnection)clients[data[0]];
sender.RemoteAdd = Remote;
if (data.Length > 2)
{
OnLineRecieved(sender, data[1] + "|" + data[2]);
}
else
{
OnLineRecieved(sender, data[1]);
}
}
}
Setup Information for a user connection Server-side:
Socket trans = new Socket(AddressFamily.InterNetwork,
SocketType.Dgram, ProtocolType.Udp); //UDP connection for data transmission in game.
public PlayerLoc Location = new PlayerLoc();
public UserConnection(TcpClient client)//TCP connection established first in the Constructor
{
this.client = client;
ipAdd = IPAddress.Parse(((IPEndPoint)client.Client.RemoteEndPoint).Address.ToString());
ipep = new IPEndPoint(ipAdd, ((IPEndPoint)client.Client.RemoteEndPoint).Port);
this.client.GetStream().BeginRead(readBuffer, 0, READ_BUFFER_SIZE, new AsyncCallback(StreamReciever), null);
}
Method for sending data to individual users:
public void SendData(string data)//UDP only used during transmission
{
byte[] dataArr = Encoding.ASCII.GetBytes(data);
trans.SendTo(dataArr, dataArr.Length,SocketFlags.None, RemoteAdd);
}

The client must start the UDP communication so that it can get a "hole" in the router/firewall. And the UDP server must reply back using the end point referenced in ReceviedFrom