Develop Reference

sr.ReadLine() isn't receiving data that is being sent

I am trying to implement an authentication method for my program. I have a server-side program that handles authentication:
class Program
{
static TcpListener listener = new TcpListener(9120);
public const string DECRYPT_KEY = "KObOBonONoinbOClHNKYJkgIKUFkjfKcvCYckcvBBCVKcbvHHCxthjcTJYBXJahjh";
static void Main(string[] args)
{
listener.Start();
while (true)
{
if (listener.Pending())
{
new Thread(TryAuthenticate).Start();
}
}
}
static void TryAuthenticate()
{
TcpClient needsAuth = listener.AcceptTcpClient();
StreamReader sr = new StreamReader(needsAuth.GetStream());
string line = sr.ReadLine();
if (!line.StartsWith("AUTH? ")) return;
StreamReader sr2 = new StreamReader("keys.pks");
string line2;
while ((line2 = sr2.ReadLine()) != null)
{
if (line == line2)
{
new StreamWriter(needsAuth.GetStream()).WriteLine("AFFIRMATIVE");
sr.Close();
}
}
sr2.Close();
needsAuth.Close();
}
}
And on the client-side I have this code:
class Authentication
{
public static bool Authenticate(string id)
{
if (id == "dEbUg2020") return true;
TcpClient client = new TcpClient("127.0.0.1", 9120);
StreamWriter sw = new StreamWriter(client.GetStream());
StreamReader sr = new StreamReader(client.GetStream());
sw.WriteLine("AUTH? " + id);
if (sr.ReadLine() == "AFFIRMATIVE")
{
sw.Close();
sr.Close();
client.Close();
return true;
}
else
{
sw.Close();
sr.Close();
client.Close();
return false;
}
}
}
I have tried debugging on both the client and the server side.
On the client-side, it starts hanging at if (sr.ReadLine() == "AFFIRMATIVE").
On the server-side, it starts hanging at string line = sr.ReadLine();.
I have done some research and it has told me that when sr.ReadLine() is expecting data but doesn't get any, it hangs until it does.
But I have sent data, and both the client/server hangs indefinitely until it crashes. I am stuck, does anyone know why this isn't working?

After writing a message with your sw StreamWriter, you need to flush it with sw.Flush(); for it to actually be sent to the other side.
So
sw.WriteLine("Some line");
sw.Flush();
Otherwise, you're not sending anything.

Named Pipe Input Output in C#

I am working with named pipes and very confused about how the interaction between the client and server is happening.
My server is a VM with a named pipe attached to it. I have created a client stream in C# this way:
NamedPipeClientStream client = new NamedPipeClientStream(".", "TestPipe", PipeDirection.InOut);
Let's say the VM prompt is like below:
Hello!
Do you accept (y/n): y
Text1 : 1.2.3.4
Text2 : 2.3.4.5
What I essentially need to do is, check if the line read by the stream is "Do you accept (y/n):", if it matches then write y to the stream.es with Text1, then write 1.2.3.4 in the stream
Problems I am facing:
The prompt doesn't display anything after Hello!. What I thought
is, it is maybe waiting for the next input. So, instead of doing
this:
if(line.contains("Do you accept (y/n):"))
writer.writeLine("y")
I did this:
if(line.contains("Hello!"))
writer.writeLine("y");
Is this the correct thing? If it is, then it means that the server
isn't pushing the text in the buffer on which it is awaiting input.
So, every time I'll have to do the check for the previous line and
write the output of the next expected line to the writer stream?
Also, as per above, for passing 1.2.3.4 for Text1, I did this:
if(line.contains("Do you accept (y/n):"))
writer.writeLine("1.2.3.4")
What appears in my execution prompt is: Text1 : 1111111 ie. it's
only repeating the first character of the input I have passed. Why
such? I have already set AutoFlush = true to my writer stream.
Any pointers here will be highly appreciated!
Edit: Including the snippet
using System;
using System.IO;
using System.IO.Pipes;
using System.Linq;
using System.Windows;
namespace App1 {
static void Main(string [] args) {
NamedPipeClientStream client = new NamedPipeClientStream(".", "TestPipe", PipeDirection.InOut);
while(!client.IsConnected);
Streamreader reader = new StreamReader(client);
StreamWriter writer = new StreamWriter(client);
string line = "";
writer.AutoFlush = true;
while((line = reader.readLine()) != null) {
if(line.Contains("Hello!") {
writer.writeLine("1.2.3.4"); // input for the next prompt
}
else if(line.Contains("Text1") {
writer.writeLine("2.3.4.5"); // input for next prompt of Text2
}
writer.Flush();
writer.WaitForPipeDrain();
}
}
}
Is above the right way?
Also, sometimes the pipe reader is missing data. Like it shows Tet1 instead of Text1. Why such?

You have this statement: while(!client.IsConnected); which causes the client to wait for the connection before proceeding. However, the client never attempts to connect (client.Connect();), so presumably you will be waiting forever. Replace that line with if (!client.IsConnected) {client.Connect();} to get this to work.
Beyond that, per the comments, without knowing what your server side code looks like it's hard to say what the client should be sending; as the two sides are having a scripted conversation.
Here's an example of some working server & client code to illustrate how you could perform this conversation:
Code to kick off both client & server:
static void Main()
{
var server = Task.Factory.StartNew(() => RunServer());
var client = Task.Factory.StartNew(() => RunClient());
Task.WaitAll(server, client);
Console.WriteLine("Done");
}
Client code:
static void RunClient()
{
using (var pipeClient = new NamedPipeClientStream(".", "TestPipe", PipeDirection.InOut))
{
Console.WriteLine("Client is waiting to connect");
if(!pipeClient.IsConnected){pipeClient.Connect();}
Console.WriteLine("Client is connected");
using (var reader = new StreamReader(pipeClient))
{
using (var writer = new StreamWriter(pipeClient))
{
var running = true;
while(running)
{
Console.WriteLine("Client is waiting for input");
var message = reader.ReadLine();
if (message != null)
{
Console.WriteLine("Client: Recieved from server {0}", message);
switch (message)
{
case "Do you accept (y/n):":
writer.WriteLine("y");
writer.WriteLine("quit");
writer.Flush();
break;
case "quit":
running = false;
break;
}
}
}
}
}
}
Console.WriteLine("Client Quits");
}
Server code:
static void RunServer()
{
using (var pipeServer = new NamedPipeServerStream("TestPipe", PipeDirection.InOut))
{
using (var reader = new StreamReader(pipeServer))
{
using (var writer = new StreamWriter(pipeServer))
{
var running = true;
Console.WriteLine("Server is waiting for a client");
pipeServer.WaitForConnection();
Console.WriteLine("Server has connection from client");
Console.WriteLine("Server: Saying Hi");
writer.WriteLine("Hello!");
Console.WriteLine("Server: Prompting for Input");
writer.WriteLine("Do you accept (y/n):");
writer.Flush();
while(running)
{
pipeServer.WaitForPipeDrain();
var message = reader.ReadLine();
Console.WriteLine("Server: Recieved from client {0}", message);
if (message.Equals("quit"))
{
writer.WriteLine("quit");
running = false;
}
}
}
}
}
Console.WriteLine("Server Quits");
}
Update
Amended code to read characters rather than lines; so we don't have to wait for a line break before seeing the server's messages.
//using System.Threading.Tasks;
//using System.IO.Pipes;
static void Main()
{
var server = Task.Factory.StartNew(() => RunServer());
var client = Task.Factory.StartNew(() => RunClient());
Task.WaitAll(server, client);
Console.WriteLine("Done");
}
static void RunClient()
{
using (var pipeClient = new NamedPipeClientStream(".", "TestPipe", PipeDirection.InOut))
{
Console.WriteLine("Client is waiting to connect");
if(!pipeClient.IsConnected){pipeClient.Connect();}
Console.WriteLine("Client is connected");
using (var reader = new StreamReader(pipeClient))
{
using (var writer = new StreamWriter(pipeClient))
{
var message = string.Empty;
var running = true;
while(running)
{
Console.WriteLine("Client is waiting for input");
var chr = reader.Read();
if (chr >= 32)
{
message = message + (char)chr;
Console.WriteLine("Client: Recieved from server {0}", message);
switch (message)
{
case "Do you accept (y/n):":
writer.WriteLine("y");
writer.WriteLine("quit");
writer.Flush();
break;
case "quit":
running = false;
break;
}
}
else {
message = string.Empty;
Console.WriteLine("Client: New Line Received from Server");
}
}
}
}
}
Console.WriteLine("Client Quits");
}
static void RunServer()
{
using (var pipeServer = new NamedPipeServerStream("TestPipe", PipeDirection.InOut))
{
using (var reader = new StreamReader(pipeServer))
{
using (var writer = new StreamWriter(pipeServer))
{
var running = true;
Console.WriteLine("Server is waiting for a client");
pipeServer.WaitForConnection();
Console.WriteLine("Server has connection from client");
Console.WriteLine("Server: Saying Hi");
writer.WriteLine("Hello!");
Console.WriteLine("Server: Prompting for Input");
writer.Write("Do you accept (y/n):"); //NB: This is a write, not a write line!
writer.Flush();
while(running)
{
pipeServer.WaitForPipeDrain();
var message = reader.ReadLine();
Console.WriteLine("Server: Recieved from client {0}", message);
switch (message)
{
case "quit":
writer.WriteLine("quit");
running = false;
break;
default:
writer.WriteLine("");
break;
}
}
}
}
}
Console.WriteLine("Server Quits");
}
So this is what your code should look like:
int charAsInt;
var line = string.Empty;
while(((charAsInt = reader.Read()) != -1)) {
if (charAsInt >= 32) { //is a displayable character
line = line + (char)charAsInt;
//your code to handle the lines
if(line.Contains("Hello!")) {
writer.WriteLine("1.2.3.4"); // input for the next prompt
} else if(line.Contains("Text1") {
writer.WriteLine("2.3.4.5"); // input for next prompt of Text2
}
writer.Flush();
//writer.WaitForPipeDrain();
} else { //is a control character
if (charAsInt == 10 || charAsInt == 13) { //carriage return or line feed; i.e. end of line
if (line.Length > 0) {
Debug.WriteLine("Last line read was {0}", line); //just so you can see info as it comes from the server
line = string.Empty;
}
}
}
}

Async socket server with multiple clients

i have a problem i am unable to resolve as my c# knowledge is not very good.
I found some code on the internet and modified it according to my needs.
My problem is that when i send messages to clients only one receives the message, then the next message is received by another client and so on.
I want to send same message to all connected clients without losing any data.
Server
using System;
using System.Net.Sockets;
using System.Threading;
public class AsynchIOServer
{
static TcpListener tcpListener = new TcpListener(10);
static void Listeners()
{
Socket socketForClient = tcpListener.AcceptSocket();
if (socketForClient.Connected)
{
Console.WriteLine("Client:"+socketForClient.RemoteEndPoint+" now connected to server.");
NetworkStream networkStream = new NetworkStream(socketForClient);
System.IO.StreamWriter streamWriter =
new System.IO.StreamWriter(networkStream);
System.IO.StreamReader streamReader =
new System.IO.StreamReader(networkStream);
////here we send message to client
while (true){
Console.WriteLine("type your message to be recieved by client:");
string theString = Console.ReadLine();
streamWriter.WriteLine(theString);
////Console.WriteLine(theString);
streamWriter.Flush();
}
streamReader.Close();
networkStream.Close();
streamWriter.Close();
}
socketForClient.Close();
Console.WriteLine("Press any key to exit from server program");
Console.ReadKey();
}
public static void Main()
{
//TcpListener tcpListener = new TcpListener(10);
tcpListener.Start();
Console.WriteLine("************This is Server program************");
Console.WriteLine("Hoe many clients are going to connect to this server?:");
int numberOfClientsYouNeedToConnect =int.Parse( Console.ReadLine());
for (int i = 0; i < numberOfClientsYouNeedToConnect; i++)
{
Thread newThread = new Thread(new ThreadStart(Listeners));
newThread.Start();
}
}
}
Client:
using System;
using System.Net.Sockets;
using System.Threading;
public class Client
{
static public void Main(string[] Args)
{
TcpClient socketForServer;
try
{
socketForServer = new TcpClient("localHost", 10);
}
catch
{
Console.WriteLine(
"Failed to connect to server at {0}:999", "localhost");
return;
}
NetworkStream networkStream = socketForServer.GetStream();
System.IO.StreamReader streamReader =
new System.IO.StreamReader(networkStream);
System.IO.StreamWriter streamWriter =
new System.IO.StreamWriter(networkStream);
Console.WriteLine("*******This is client program who is connected to localhost on port No:10*****");
try
{
string outputString;
// read the data from the host and display it
{
while (true)
{
outputString = streamReader.ReadLine();
Console.WriteLine("Message Recieved by server:" + outputString);
streamWriter.Flush();
}
}
}
catch
{
Console.WriteLine("Exception reading from Server");
}
// tidy up
networkStream.Close();
Console.WriteLine("Press any key to exit from client program");
Console.ReadKey();
}
private static string GetData()
{
//Ack from sql server
return "ack";
}
}
Thank you

simple working multi-threaded server:
static void Process(Socket client) {
Console.WriteLine("Incoming connection from " + client.RemoteEndPoint);
const int maxMessageSize = 1024;
byte[] response;
int received;
while (true) {
// Send message to the client:
Console.Write("Server: ");
client.Send(Encoding.ASCII.GetBytes(Console.ReadLine()));
Console.WriteLine();
// Receive message from the server:
response = new byte[maxMessageSize];
received = client.Receive(response);
if (received == 0) {
Console.WriteLine("Client closed connection!");
return;
}
List<byte> respBytesList = new List<byte>(response);
respBytesList.RemoveRange(received, maxMessageSize - received); // truncate zero end
Console.WriteLine("Client (" + client.RemoteEndPoint + "+: " + Encoding.ASCII.GetString(respBytesList.ToArray()));
}
}
static void Main(string[] args) {
int backlog = -1, port = 2222;
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
server.ReceiveTimeout = -1;
// Start listening.
try {
server.Bind(new IPEndPoint(IPAddress.Any, port));
server.Listen(backlog);
}
catch (Exception) {
Console.WriteLine("Listening failed!");
Console.ReadKey();
return;
}
Console.WriteLine("Start listening...");
while(true) {
Socket client = server.Accept();
new System.Threading.Thread(() => {
try { Process(client); } catch (Exception ex) { Console.WriteLine("Client connection processing error: " + ex.Message); }
}).Start();
}
//Console.WriteLine("Press any key for exit...");
//Console.ReadKey();
}
And client:
static void WorkWithServer(Socket server) {
const int maxMessageSize = 1024;
byte[] response;
int received;
while(true) {
try {
// Receive message from the server:
response = new byte[maxMessageSize];
received = server.Receive(response);
if (received == 0) {
Console.WriteLine("Server closed connection.");
return;
}
List<byte> respBytesList = new List<byte>(response);
respBytesList.RemoveRange(received, maxMessageSize - received); // truncate zero end
Console.WriteLine("Server: " + Encoding.ASCII.GetString(respBytesList.ToArray()));
// Send message to the server:
Console.Write("You: ");
server.Send(Encoding.ASCII.GetBytes(Console.ReadLine()));
Console.WriteLine();
}
catch (Exception ex) {
Console.WriteLine("Error: " + ex.Message);
return;
}
}
}
static void Main(string[] args) {
IPEndPoint serverEp = new IPEndPoint(IPAddress.Parse("192.168.1.2"), 2222);
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
server.ReceiveTimeout = -1;
// Connect to the server.
try { server.Connect(serverEp); }
catch (Exception) {
Console.WriteLine("Establish connection with server (" + serverEp + ") failed!");
Console.ReadKey();
return;
}
Console.WriteLine("Connection with server (" + serverEp + ") established!");
WorkWithServer(server);
Console.WriteLine("Press any key for exit...");
Console.ReadKey();
}
Edit as you need.

Your code is wrong.
First of all I'll give you some insight of how it's wrong and why it's not working the way you want.
You're creating n number of threads, and making them ALL wait for a connection. What if you exhaust the number of threads? What if any of them exits unexpectedly?
You are also sending the data wrong. By using Console.ReadLine you aren't passing the data through multiple threads and reading the line in each one, instead, the first one that calls Console.ReadLine will be the one that's going to receive it. This means you'll only be sending to only one Socket.
It's not ideal how you're managing this. There are dozens if not hundreds of multithreaded socket server/client available online, and I'd invite you to research a little bit more. But first I'd like you to research more about Thread/Task in C#.

Auto flush of tcp stream doesn't work

As you may see I work a little SMTP server written in C#.
I included whole code (one class is not included), but I hope you get good view of detail.
I am struggeling at the DATA post from the client, the problem is in my point of view the not working "Auto Flush".
The client sends to my server "DATA" to tell me to get ready to receive data for my email.
I need to answer "354 start mail input", which I do, my problem is:
After sending "354 start mail input" I need to receive the message from client in this funtion.
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace FakeSMTP
{
public class SMTPServer //: IDisposable
{
TcpClient client;
NetworkStream stream;
System.IO.StreamReader reader;
System.IO.StreamWriter writer;
//public void Dispose()
//{
// writer.Dispose();
// reader.Dispose();
// stream.Dispose();
//}
public SMTPServer(TcpClient client)
{
this.client = client;
stream = client.GetStream();
reader = new System.IO.StreamReader(stream);
writer = new System.IO.StreamWriter(stream);
writer.NewLine = "\r\n";
writer.AutoFlush = true;
}
static void Main(string[] args)
{
TcpListener listener = new TcpListener(IPAddress.Loopback, 25);
listener.Start();
//using (SMTPServer handler = new SMTPServer(listener.AcceptTcpClient()))
while (true)
{
SMTPServer handler = new SMTPServer(listener.AcceptTcpClient());
Thread thread = new System.Threading.Thread(new ThreadStart(handler.Run));
thread.Start();
}
}
public void Run()
{
string sadress;
string radress;
string rserver;
bool auth = false;
writer.WriteLine("220 smtp.localsmtp.de ESMTP server ready");
for (string line = reader.ReadLine(); line != null; line = reader.ReadLine())
{
Console.Error.WriteLine("Read line {0}", line);
if (line.StartsWith("EHLO"))
{
writer.WriteLine("250-smtp.localsmtp.de");
//Auth ankuendigen
writer.WriteLine("250 AUTH PLAIN");
}
if (line.StartsWith("QUIT"))
{
writer.WriteLine("221 Bye Sweetie see ya");
client.Close();
}
#region auth
if (line.StartsWith("AUTH PLAIN"))
{
Console.WriteLine("client sendet Auth: " + line);
string [] pw = line.Split(new string[] { "PLAIN " }, StringSplitOptions.None);
byte[] bytes = Convert.FromBase64String(pw[1]);
string result = Encoding.BigEndianUnicode.GetString(bytes);
if (result == "12")
{
writer.WriteLine("235 2.7.0 Authentication successful");
auth = true;
}
else
{
Console.WriteLine("Falsche AUTH Daten");
writer.WriteLine("535 – Incorrect authentication data");
}
}
#endregion
#region sender
if (line.StartsWith("MAIL FROM") && auth == true)
{
string[] sadressa = line.Split(new string[] { "FROM:" }, StringSplitOptions.None);
sadress = sadressa[1];
//Absender
sadress = sadress.Replace("<","").Replace(">","");
//Debug
Console.WriteLine("Absender: " + sadress);
writer.WriteLine("250 OK");
}
#endregion
#region receiver
if (line.StartsWith("RCPT TO:") && auth == true)
{
string[] radressa = line.Split(new string[] { "RCPT TO:" }, StringSplitOptions.None);
radress = radressa[1];
//Empfänger
radress = radress.Replace("<", "").Replace(">", "");
if (samplesmtp.getMX.GetMXRecord(radress) != "invalid")
{
rserver = samplesmtp.getMX.GetMXRecord(radress);
Console.WriteLine("MX Record: " + rserver);
}
else
Console.WriteLine("ALARM");
//Debug
Console.WriteLine("Empfänger: " + radress);
writer.WriteLine("250 OK");
}
#endregion
#region data
if (line.StartsWith("DATA") && auth == true)
{
writer.WriteLine("354 start mail input");
var emailLine = reader.ReadLine();
while (!emailLine.Equals("."))
{
// add emailLine to the email body
string[] emailbody = new string[] {emailLine};
Console.WriteLine("Emailbody: " + emailbody[0]);
}
reader.Close();
writer.Close();
stream.Dispose();
writer.WriteLine("250 OK");
}
#endregion
}
}
}
}
Trying to call .Flush() manually in code doesn't change the problem at all. No effect.

In answer to your actual question you want to read all the lines until you receive a . on a line on it's own (see https://www.ietf.org/rfc/rfc2821.txt), something like this: -
var emailLine = reader.ReadLine();
while (!emailLine.Equals("."))
{
// add emailLine to the email body
emailLine = reader.readLine();
}
writer.WriteLine("250 OK");
reader.Close();
writer.Close();
stream.Dispose();

In response to your comment to mine:
public class SMTPServer : IDisposable
{
// all the other stuff
public void Dispose()
{
writer.Dispose();
reader.Dispose();
stream.Dispose();
}
}
calling code:
static void Main(string[] args)
{
TcpListener listener = new TcpListener(IPAddress.Loopback, 25);
listener.Start();
using (SMTPServer handler = new SMTPServer(listener.AcceptTcpClient()))
{
while (true)
{
Thread thread = new System.Threading.Thread(new ThreadStart(handler.Run));
thread.Start();
}
}
}

Threading issue in C#

can somebody tell me why my code is not working?
class Connection
{
public static StreamWriter writer;
public static string SERVER;
private static int PORT;
private static string USER;
private static string NICK;
private static string CHANNELS;
private Thread connection;
private Thread ping;
public Connection()
{
connection = new Thread(new ThreadStart(this.Run));
ping = new Thread(new ThreadStart(this.Ping));
}
public void Start(string server, int port, string ident, string realname, string nick, string channels)
{
SERVER = server;
PORT = port;
USER = "USER " + ident + " 8 * :" + realname;
NICK = nick;
CHANNELS = channels;
connection.Start();
}
public void Ping()
{
while (true)
{
try
{
Connection.writer.WriteLine("PING :" + SERVER);
Connection.writer.Flush();
Thread.Sleep(15000);
}
catch (Exception e) { Console.WriteLine(e.ToString()); }
}
}
public void Run()
{
NetworkStream stream;
TcpClient irc;
string inputLine;
StreamReader reader;
try
{
irc = new TcpClient(SERVER, PORT);
stream = irc.GetStream();
reader = new StreamReader(stream);
writer = new StreamWriter(stream);
writer.WriteLine(USER);
writer.Flush();
writer.WriteLine("NICK " + NICK);
writer.Flush();
Thread.Sleep(5000);
writer.WriteLine("JOIN " + CHANNELS);
writer.Flush();
while (true)
{
while ((inputLine = reader.ReadLine()) != null)
{
Console.WriteLine(inputLine);
}
writer.Close();
reader.Close();
irc.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
Thread.Sleep(5000);
Run();
}
}
}
It connects to the server fine, but the ping Thread and voids seem to not functioning at all! and i dont know why, everything seems correct unless im missing something very obviousC

You haven't started your ping thread. Call Start method of it.
Another note - don't use Thread.Sleep for threads/process synchronization. From my experience, code using it is usually slow, unreliable and hard to maintain. Use Monitor class or various WaitHandle implementations (e.g. AutoResetEvent) or whatever. For client/server communication try to wait until server response to your request (if such is defined in protocol), not just timeout.
Also, if you are starting new threads either make this threads stop (e.g. in Dispose method of your class) or set IsBackground property, or, preferrably, both. Otherwise these threads will block your process from stopping.