Develop Reference

Unable to read data from tcp server

I have created a simple C# client application. Once it connects to the server it should read the messages sent from the server. It also has the ability to send messages to server too. However I am unable to figure out to correct way to read the data.
I am spawning a thread once it connects to the server. The thread runs in infinite loop and have two interfaces each for reading and writing. Connect() method is called from a ButtonClick event.
My code snippet is as below:
namespace WpfApp1
{
public class TCPClientClass
{
private StreamWriter SwSender;
NetworkStream Sender;
NetworkStream Receiver;
//private StreamReader SrReciever;
private Thread thrMessaging;
TcpClient tcp;
bool connected = false;
public bool Connected { get { return connected; } set { connected = value; } }
//public bool Connect(IPAddress IP, int nPortNo)
public async Task Connect(IPAddress IP, int nPortNo)
{
tcp = new TcpClient();
try
{
//tcp.Connect(strIPAddress.Parse("192.168.137.1"), 2000);
// tcp.Connect(IP , nPortNo);
await tcp.ConnectAsync(IP, nPortNo);
thrMessaging = new Thread(new ThreadStart(ThreadFunction));
thrMessaging.Start();
Connected = true;
}
catch
{
MessageBox.Show("Unable to connect to server");
//return false;
}
//return true;
}
public void Disconnect()
{
Sender?.Close();
Receiver?.Close();
tcp?.Close();
//tcp?.Client.Disconnect(false);
thrMessaging.Abort();
Connected = false;
}
private void ThreadFunction()
{
while (thrMessaging.IsAlive)
DoTasks();
}
private void DoTasks()
{
if (Connected)
{
var a = ReadMessages();
SendMessages();
}
}
private /*void*/async Task ReadMessages()
{
byte[] data = new byte[4096];
//Int32 bytesRead = 0;
//Task<int> bytesReadTask;
String responseData = String.Empty;
Receiver = tcp.GetStream();
try
{
//bytesReadTask = Receiver.ReadAsync(data, 0, data.Length);
//responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytesReadTask.Result);
var response = await Receiver.ReadAsync(data, 0, data.Length);
MessageBox.Show("Server response was " + response);
Thread.Sleep(1000);
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
}
private void SendMessages()
{
try
{
string strSendData = "Hello from GUI";
Byte[] data = System.Text.Encoding.ASCII.GetBytes(strSendData);
Sender = tcp.GetStream();
Sender.Write(data, 0, data.Length);
Sender.Flush();
Thread.Sleep(1000);
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
}
}
}

you should change
var response = await Receiver.ReadAsync(data, 0, data.Length);
MessageBox.Show("Server response was " + response);
to
var response = await Receiver.ReadAsync(data, 0, data.Length);
string result = System.Text.Encoding.Default.GetString(data);
MessageBox.Show("Server response was " + result);
if you´re still having problems..my server Code:
public class tcpServer
{
public void method()
{
TcpListener server = new TcpListener(IPAddress.Any, 9999);
server.Start();
TcpClient client = server.AcceptTcpClient();
NetworkStream ns = client.GetStream();
byte[] hello = new byte[100];
hello = Encoding.Default.GetBytes("hello world");
while (client.Connected)
{
ns.Write(hello, 0, hello.Length);
}
}
}

Async TCPClient missing replies from server

I'm trying to implement an async TCP client that sends messages from a queue and listens to the response.
some of the server replies are lost (for example send 7 messages and get only 4 replies) and I don't understand why.
This is not a server issue, since the synchronize version I tested works just fine.
ConcurrentQueue<byte[]> msgQueue = new ConcurrentQueue<byte[]>();
public void Connect()
{
try
{
tcpclnt = new TcpClient();
Console.WriteLine("Connecting.....");
Task.Factory.StartNew(() =>
{
IAsyncResult res = tcpclnt.BeginConnect(_ip, _port, null, null);
if (!res.AsyncWaitHandle.WaitOne(CONNECTION_TIMEOUT_SEC * 1000))
{
tcpclnt.Close();
throw new ApplicationException("timed out trying to connect");
}
tcpclnt.EndConnect(res);
Receive();
byte[] message = null;
while (true)
{
message = null;
msgQueue.TryDequeue(out message);
if (message != null)
{
Stream stm = tcpclnt.GetStream();
Console.WriteLine("Transmitting..... " + Thread.CurrentThread.ManagedThreadId);//for debug
stm.Write(message.ToArray(), 0, message.ToArray().Length);
Receive();
}
}
});
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
//will be called from outside
public void SendMessage(byte[] msg)
{
Console.WriteLine("SendMessage..... " + Thread.CurrentThread.ManagedThreadId);//for debug
msgQueue.Enqueue(msg);
}
private void Receive()
{
SocketError error;
byte[] buffer = new byte[MAX_BUFFER_SIZE];
tcpclnt.Client.BeginReceive(buffer, 0, MAX_BUFFER_SIZE, SocketFlags.None, out error, new AsyncCallback(ReceiveHandler), buffer);
}
private void ReceiveHandler(IAsyncResult ar)
{
System.Console.WriteLine("ReceiveHandler " + Thread.CurrentThread.ManagedThreadId); //for debug
//End current async receive
int bytesRead = tcpclnt.Client.EndReceive(ar);
byte[] resultBuffer = (byte[]) ar.AsyncState;
// do a lot of things with resultBuffer
}

How to read and send data to client from server?

I'm trying to make a server client using a local console server on my pc and a client on windows phone 8.1. The problem that I have is that I don't know how to read the incoming data from the client. I've searched the internet and read serveral microsoft tutorials but they do not explain how to read the incoming data in the server. Here's what I have.
Client on windows phone 8.1:
private async void tryConnect()
{
if (connected)
{
StatusLabel.Text = "Already connected";
return;
}
try
{
// serverHostnameString = "127.0.0.1"
// serverPort = "1330"
StatusLabel.Text = "Trying to connect ...";
serverHost = new HostName(serverHostnameString);
// Try to connect to the
await clientSocket.ConnectAsync(serverHost, serverPort);
connected = true;
StatusLabel.Text = "Connection established" + Environment.NewLine;
}
catch (Exception exception)
{
// If this is an unknown status,
// it means that the error is fatal and retry will likely fail.
if (SocketError.GetStatus(exception.HResult) == SocketErrorStatus.Unknown)
{
throw;
}
StatusLabel.Text = "Connect failed with error: " + exception.Message;
// Could retry the connection, but for this simple example
// just close the socket.
closing = true;
// the Close method is mapped to the C# Dispose
clientSocket.Dispose();
clientSocket = null;
}
}
private async void sendData(string data)
{
if (!connected)
{
StatusLabel.Text = "Must be connected to send!";
return;
}
UInt32 len = 0; // Gets the UTF-8 string length.
try
{
StatusLabel.Text = "Trying to send data ...";
// add a newline to the text to send
string sendData = "jo";
DataWriter writer = new DataWriter(clientSocket.OutputStream);
len = writer.MeasureString(sendData); // Gets the UTF-8 string length.
// Call StoreAsync method to store the data to a backing stream
await writer.StoreAsync();
StatusLabel.Text = "Data was sent" + Environment.NewLine;
// detach the stream and close it
writer.DetachStream();
writer.Dispose();
}
catch (Exception exception)
{
// If this is an unknown status,
// it means that the error is fatal and retry will likely fail.
if (SocketError.GetStatus(exception.HResult) == SocketErrorStatus.Unknown)
{
throw;
}
StatusLabel.Text = "Send data or receive failed with error: " + exception.Message;
// Could retry the connection, but for this simple example
// just close the socket.
closing = true;
clientSocket.Dispose();
clientSocket = null;
connected = false;
}
}
(from http://msdn.microsoft.com/en-us/library/windows/apps/xaml/jj150599.aspx)
And the server:
public class Server
{
private TcpClient incomingClient;
public Server()
{
TcpListener listener = new TcpListener(IPAddress.Parse("127.0.0.1"), 1330);
listener.Start();
Console.WriteLine("Waiting for connection...");
while (true)
{
//AcceptTcpClient waits for a connection from the client
incomingClient = listener.AcceptTcpClient();
//start a new thread to handle this connection so we can go back to waiting for another client
Thread thread = new Thread(HandleClientThread);
thread.IsBackground = true;
thread.Start(incomingClient);
}
}
private void HandleClientThread(object obj)
{
TcpClient client = obj as TcpClient;
Console.WriteLine("Connection found!");
while (true)
{
//how to read and send data back?
}
}
}
It comes to the point where the server prints 'Connection found!', but I don't know how to go further.
Any help is appreciated!
EDIT:
Now my handleclientthread method looks like this:
private void HandleClientThread(object obj)
{
TcpClient client = obj as TcpClient;
netStream = client.GetStream();
byte[] rcvBuffer = new byte[500]; // Receive buffer
int bytesRcvd; // Received byte count
int totalBytesEchoed = 0;
Console.WriteLine("Connection found!");
while (true)
{
while ((bytesRcvd = netStream.Read(rcvBuffer, 0, rcvBuffer.Length)) > 0)
{
netStream.Write(rcvBuffer, 0, bytesRcvd);
totalBytesEchoed += bytesRcvd;
}
Console.WriteLine(totalBytesEchoed);
}
}
But it still doesn't write the bytes to the console

So... after a lot of searching the internet I have found a solution...
Server: to read from the server and send data back to the phone:
// method in a new thread, for each connection
private void HandleClientThread(object obj)
{
TcpClient client = obj as TcpClient;
netStream = client.GetStream();
Console.WriteLine("Connection found!");
while (true)
{
// read data
byte[] buffer = new byte[1024];
int totalRead = 0;
do
{
int read = client.GetStream().Read(buffer, totalRead, buffer.Length - totalRead);
totalRead += read;
} while (client.GetStream().DataAvailable);
string received = Encoding.ASCII.GetString(buffer, 0, totalRead);
Console.WriteLine("\nResponse from client: {0}", received);
// do some actions
byte[] bytes = Encoding.ASCII.GetBytes(received);
// send data back
client.GetStream().WriteAsync(bytes, 0, bytes.Length);
}
}
Phone(client): to send messages from the phone and read the messages from server:
private async void sendData(string dataToSend)
// import for AsBuffer(): using System.Runtime.InteropServices.WindowsRuntime;
{
if (!connected)
{
StatusLabel.Text = "Status: Must be connected to send!";
return;
}
try
{
byte[] data = GetBytes(dataToSend);
IBuffer buffer = data.AsBuffer();
StatusLabel.Text = "Status: Trying to send data ...";
await clientSocket.OutputStream.WriteAsync(buffer);
StatusLabel.Text = "Status: Data was sent" + Environment.NewLine;
}
catch (Exception exception)
{
if (SocketError.GetStatus(exception.HResult) == SocketErrorStatus.Unknown)
{
throw;
}
StatusLabel.Text = "Status: Send data or receive failed with error: " + exception.Message;
closing = true;
clientSocket.Dispose();
clientSocket = null;
connected = false;
}
readData();
}
private async void readData()
{
StatusLabel.Text = "Trying to receive data ...";
try
{
IBuffer buffer = new byte[1024].AsBuffer();
await clientSocket.InputStream.ReadAsync(buffer, buffer.Capacity, InputStreamOptions.Partial);
byte[] result = buffer.ToArray();
StatusLabel.Text = GetString(result);
}
catch (Exception exception)
{
if (SocketError.GetStatus(exception.HResult) == SocketErrorStatus.Unknown)
{
throw;
}
StatusLabel.Text = "Receive failed with error: " + exception.Message;
closing = true;
clientSocket.Dispose();
clientSocket = null;
connected = false;
}
}
The 'await clientSocket.InputStream.ReadAsync(buffer, buffer.Capacity, InputStreamOptions.Partial)' command in the readData method was very unclear for me. I didn't know you had to make a new buffer, and the ReadAsync-method fills it(as i inderstand it). Found it here: StreamSocket.InputStreamOptions.ReadAsync hangs when using Wait()

Java TCP Client doesn't receive messages sent from C# Server

I'm writing a tcp server in c# and corresponding client in java. I'm testing the connection on localhost, and the client is able to connect to the server. However, when I'm sending messages, the client never receives them. Using the debugger I've verified that stream.Write(...) is executed. Any idea what the problem could be?
This is the c# server:
TcpClient client = (TcpClient)cl;
NetworkStream stream = client.GetStream();
byte[] msg = new byte[512];
int bytesRead;
while (running)
{
while (messages.getCount() > 0)
{
String msg = messages.Take();
if (cmd != null)
{
byte[] bytes = Encoding.UTF8.GetBytes(msg.ToCharArray());
try
{
stream.Write(bytes, 0, bytes.Length);
stream.Flush();
}
catch (Exception e)
{
}
}
}
Thread.Sleep(1000);
}
And the Java client:
public void run()
{
try
{
socket = new Socket(address, port);
in = new BufferedReader( new InputStreamReader( socket.getInputStream() ));
out = new PrintWriter(socket.getOutputStream());
running = true;
}
catch (Exception e){
e.printStackTrace();
running = false;
}
String data;
while(running)
{
try
{
data = in.readLine();
if(data != null)
{
processData(data);
}
}
catch (IOException e)
{
e.printStackTrace();
running = false;
break;
}
}
try
{
socket.close();
socket = null;
}
catch (IOException e)
{
e.printStackTrace();
}
running = false;
}

You're using BufferedReader.readLine(). Are your message strings terminated by a CR, LF, or CR/LF?
readLine blocks until a line-terminating character is read.

Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host

I have an update server that sends client updates through TCP port 12000. The sending of a single file is successful only the first time, but after that I get an error message on the server "Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host". If I restart the update service on the server, it works again only one time. I have normal multithreaded windows service.
SERVER CODE
namespace WSTSAU
{
public partial class ApplicationUpdater : ServiceBase
{
private Logger logger = LogManager.GetCurrentClassLogger();
private int _listeningPort;
private int _ApplicationReceivingPort;
private string _setupFilename;
private string _startupPath;
public ApplicationUpdater()
{
InitializeComponent();
}
protected override void OnStart(string[] args)
{
init();
logger.Info("after init");
Thread ListnerThread = new Thread(new ThreadStart(StartListener));
ListnerThread.IsBackground = true;
ListnerThread.Start();
logger.Info("after thread start");
}
private void init()
{
_listeningPort = Convert.ToInt16(ConfigurationSettings.AppSettings["ListeningPort"]);
_setupFilename = ConfigurationSettings.AppSettings["SetupFilename"];
_startupPath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase).Substring(6);
}
private void StartListener()
{
try
{
logger.Info("Listening Started");
ThreadPool.SetMinThreads(50, 50);
TcpListener listener = new TcpListener(_listeningPort);
listener.Start();
while (true)
{
TcpClient c = listener.AcceptTcpClient();
ThreadPool.QueueUserWorkItem(ProcessReceivedMessage, c);
}
}
catch (Exception ex)
{
logger.Error(ex.Message);
}
}
void ProcessReceivedMessage(object c)
{
try
{
TcpClient tcpClient = c as TcpClient;
NetworkStream Networkstream = tcpClient.GetStream();
byte[] _data = new byte[1024];
int _bytesRead = 0;
_bytesRead = Networkstream.Read(_data, 0, _data.Length);
MessageContainer messageContainer = new MessageContainer();
messageContainer = SerializationManager.XmlFormatterByteArrayToObject(_data, messageContainer) as MessageContainer;
switch (messageContainer.messageType)
{
case MessageType.ApplicationUpdateMessage:
ApplicationUpdateMessage appUpdateMessage = new ApplicationUpdateMessage();
appUpdateMessage = SerializationManager.XmlFormatterByteArrayToObject(messageContainer.messageContnet, appUpdateMessage) as ApplicationUpdateMessage;
Func<ApplicationUpdateMessage, bool> HandleUpdateRequestMethod = HandleUpdateRequest;
IAsyncResult cookie = HandleUpdateRequestMethod.BeginInvoke(appUpdateMessage, null, null);
bool WorkerThread = HandleUpdateRequestMethod.EndInvoke(cookie);
break;
}
}
catch (Exception ex)
{
logger.Error(ex.Message);
}
}
private bool HandleUpdateRequest(ApplicationUpdateMessage appUpdateMessage)
{
try
{
TcpClient tcpClient = new TcpClient();
NetworkStream networkStream;
FileStream fileStream = null;
tcpClient.Connect(appUpdateMessage.receiverIpAddress, appUpdateMessage.receiverPortNumber);
networkStream = tcpClient.GetStream();
fileStream = new FileStream(_startupPath + "\\" + _setupFilename, FileMode.Open, FileAccess.Read);
FileInfo fi = new FileInfo(_startupPath + "\\" + _setupFilename);
BinaryReader binFile = new BinaryReader(fileStream);
FileUpdateMessage fileUpdateMessage = new FileUpdateMessage();
fileUpdateMessage.fileName = fi.Name;
fileUpdateMessage.fileSize = fi.Length;
MessageContainer messageContainer = new MessageContainer();
messageContainer.messageType = MessageType.FileProperties;
messageContainer.messageContnet = SerializationManager.XmlFormatterObjectToByteArray(fileUpdateMessage);
byte[] messageByte = SerializationManager.XmlFormatterObjectToByteArray(messageContainer);
networkStream.Write(messageByte, 0, messageByte.Length);
int bytesSize = 0;
byte[] downBuffer = new byte[2048];
while ((bytesSize = fileStream.Read(downBuffer, 0, downBuffer.Length)) > 0)
{
networkStream.Write(downBuffer, 0, bytesSize);
}
fileStream.Close();
tcpClient.Close();
networkStream.Close();
return true;
}
catch (Exception ex)
{
logger.Info(ex.Message);
return false;
}
finally
{
}
}
protected override void OnStop()
{
}
}
I have to note something that my windows service (server) is multithreaded.

On the receiving end, set up a while loop to listen until there's no more data, then exit gracefully: close the stream and client. The framework TCP libs consider it an issue to drop a connection cold on thread exit and will therefore throw the exception you're seeing.
This will also save you from an intermittent problem you'll likely see once you correct the current one: Stream.Read with a length specifier won't always give you your full buffer each time. It looks like you're sending (up to) 2kb chunks and receiving into a (single-shot) 1kb buffer anyhow so you may start to get XML exceptions as well.
If that's not enough detail, ask and I'll dig up some old TcpClient code.