Develop Reference

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)
{
}
}
}
}

During TCP send breakpoint influences outcome

I have a problem with the Client/Server application i'm writing. It's aim is to send a specific directory's files in the Client and send them to a directory on the Server.
I get the files with a foreach, but when i put a breakpoint at the begin of the foreach and I continue until I send all the files I get all of them in my server as I want, when i delete the breakpoint and re-run my application, my server just receives part of the files, and i don't know why.
I'm unsure but I suppose it's a threading issue, but don't know how to solve it.
Server:
static void Main(string[] args)
{
try
{
TcpListener listen = new TcpListener(3003);
TcpClient client;
int bufferSize = 1024;
NetworkStream netStream = null;
int bytesRead = 0;
int allBytesRead = 0;
// Start listening
listen.Start();
// Accept client
client = listen.AcceptTcpClient();
StreamReader reader = new StreamReader(client.GetStream());
netStream = client.GetStream();
string fileName;
bool endOfSend=false;
do
{
fileName = reader.ReadLine();
// Read length of incoming data
byte[] length = new byte[4];
bytesRead = netStream.Read(length, 0, 4);
int dataLength = BitConverter.ToInt32(length, 0);
// Read the data
int bytesLeft = dataLength;
byte[] data = new byte[dataLength];
while (bytesLeft > 0)
{
int nextPacketSize = (bytesLeft > bufferSize) ? bufferSize : bytesLeft;
bytesRead = netStream.Read(data, allBytesRead, nextPacketSize);
allBytesRead += bytesRead;
bytesLeft -= bytesRead;
}
allBytesRead = 0;
bytesLeft = 0;
bytesRead = 0;
// Save file to desktop
Console.WriteLine("File {0} received.", fileName);
File.WriteAllBytes(#"C:\Users\toto2\Desktop\" + fileName, data);
} while (!endOfSend);
netStream.Close();
client.Close();
Console.ReadLine();
}
catch (Exception ex)
{
Console.WriteLine("File Receiving fail." + ex.Message);
}
}
Client:
static void Main(string[] args)
{
try
{
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
int port = 3003;
TcpClient client = new TcpClient();
//NetworkStream netStream;
// Connect to server
try
{
client.Connect(new IPEndPoint(ipAddress, port));
Console.WriteLine("Connecté.....");
SendFiles(client);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
// Clean up
client.Close();
Console.Read();
}
catch (Exception ex)
{
Console.WriteLine("File Sending fail." + ex.Message);
}
}
public static void SendFiles(TcpClient cli) {
NetworkStream netS=cli.GetStream();
int bufferSize = 1024;
string[] files = Directory.GetFiles(#"C:\Users\toto\Mes Images\test");
StreamWriter writer = new StreamWriter(cli.GetStream());
foreach (string item in files)
{
writer.WriteLine(Path.GetFileName(item));
writer.Flush();
// Read bytes from image
byte[] data = File.ReadAllBytes(Path.GetFullPath(item));
// Build the package
byte[] dataLength = BitConverter.GetBytes(data.Length);
byte[] package = new byte[4 + data.Length];
dataLength.CopyTo(package, 0);
data.CopyTo(package, 4);
// Send to server
int bytesSent = 0;
int bytesLeft = package.Length;
while (bytesLeft > 0)
{
int nextPacketSize = (bytesLeft > bufferSize) ? bufferSize : bytesLeft;
netS.Write(package, bytesSent, nextPacketSize);
bytesSent += nextPacketSize;
bytesLeft -= nextPacketSize;
}
}
writer.Close();
netS.Close();
}
Thank to anyone will try to help me.

You may want to implement and acknowledgement from the server to the client that it has recieved 1 file. Then instruct the client to send the next file. As far as I can tell you are just sending all the files at once. The following is a simple implementation of the acknowledgement. You should be able to take the relevant parts of it for your scenario.
//
/* Server Program */
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
public class serv {
public static void Main() {
try {
IPAddress ipAd = IPAddress.Parse("172.21.5.99");
// use local m/c IP address, and
// use the same in the client
/* Initializes the Listener */
TcpListener myList=new TcpListener(ipAd,8001);
/* Start Listeneting at the specified port */
myList.Start();
Console.WriteLine("The server is running at port 8001...");
Console.WriteLine("The local End point is :" +
myList.LocalEndpoint );
Console.WriteLine("Waiting for a connection.....");
Socket s=myList.AcceptSocket();
Console.WriteLine("Connection accepted from " + s.RemoteEndPoint);
byte[] b=new byte[100];
int k=s.Receive(b);
Console.WriteLine("Recieved...");
for (int i=0;i<k;i++)
Console.Write(Convert.ToChar(b[i]));
ASCIIEncoding asen=new ASCIIEncoding();
s.Send(asen.GetBytes("The string was recieved by the server."));
Console.WriteLine("\nSent Acknowledgement");
/* clean up */
s.Close();
myList.Stop();
}
catch (Exception e) {
Console.WriteLine("Error..... " + e.StackTrace);
}
}
}
---------------------------------------------------------------------------
/* Client Program */
using System;
using System.IO;
using System.Net;
using System.Text;
using System.Net.Sockets;
public class clnt {
public static void Main() {
try {
TcpClient tcpclnt = new TcpClient();
Console.WriteLine("Connecting.....");
tcpclnt.Connect("172.21.5.99",8001);
// use the ipaddress as in the server program
Console.WriteLine("Connected");
Console.Write("Enter the string to be transmitted : ");
String str=Console.ReadLine();
Stream stm = tcpclnt.GetStream();
ASCIIEncoding asen= new ASCIIEncoding();
byte[] ba=asen.GetBytes(str);
Console.WriteLine("Transmitting.....");
stm.Write(ba,0,ba.Length);
byte[] bb=new byte[100];
int k=stm.Read(bb,0,100);
for (int i=0;i<k;i++)
Console.Write(Convert.ToChar(bb[i]));
tcpclnt.Close();
}
catch (Exception e) {
Console.WriteLine("Error..... " + e.StackTrace);
}
}
}

You've got a hybrid binary/text protocol. That can be painful. StreamReader buffers parts of the stream. It takes more than it returns immediately as a string. You can't mix it with other readers.
Throw all of this code away and use a higher-level communication mechanism. For example WCF with MTOM for binary streaming. Or HTTP.
If you are unwilling to to that use BinaryReader ad BinaryWriter. They are reasonably easy to use.
Note, that when you read the length you assume that all 4 bytes will arrive in one read. That assumption is false.

Respond to a client using a socket?

I have two basic console apps that communicate "over the network" even though all of the communication takes place on my local machine.
Client code:
public static void Main()
{
while (true)
{
try
{
TcpClient client = new TcpClient();
client.Connect("127.0.0.1", 500);
Console.WriteLine("Connected.");
byte[] data = ASCIIEncoding.ASCII.GetBytes(new FeederRequest("test", TableType.Event).GetXmlRequest().ToString());
Console.WriteLine("Sending data.....");
using (var stream = client.GetStream())
{
stream.Write(data, 0, data.Length);
stream.Flush();
Console.WriteLine("Data sent.");
}
client.Close();
Console.ReadLine();
}
catch (Exception e)
{
Console.WriteLine("Error: " + e.StackTrace);
Console.ReadLine();
}
}
}
Server code:
public static void Main()
{
try
{
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
Console.WriteLine("Starting TCP listener...");
TcpListener listener = new TcpListener(ipAddress, 500);
listener.Start();
Console.WriteLine("Server is listening on " + listener.LocalEndpoint);
while (true)
{
Socket client = listener.AcceptSocket();
Console.WriteLine("\nConnection accepted.");
var childSocketThread = new Thread(() =>
{
Console.WriteLine("Reading data...\n");
byte[] data = new byte[100];
int size = client.Receive(data);
Console.WriteLine("Recieved data: ");
for (int i = 0; i < size; i++)
Console.Write(Convert.ToChar(data[i]));
//respond to client
Console.WriteLine("\n");
client.Close();
Console.WriteLine("Waiting for a connection...");
});
childSocketThread.Start();
}
}
catch (Exception e)
{
Console.WriteLine("Error: " + e.StackTrace);
Console.ReadLine();
}
}
How can I alter both of these applications so that when the Server has received the data, it responds to the Client with some kind of confirmation?
Thanks in advance!

Here a short example how I would do it:
Server:
class Server
{
static void Main(string[] args)
{
TcpListener listener = new TcpListener(IPAddress.Any, 1500);
listener.Start();
TcpClient client = listener.AcceptTcpClient();
NetworkStream stream = client.GetStream();
// Create BinaryWriter for writing to stream
BinaryWriter binaryWriter = new BinaryWriter(stream);
// Creating BinaryReader for reading the stream
BinaryReader binaryReader = new BinaryReader(stream);
while (true)
{
// Read incoming information
byte[] data = new byte[16];
int receivedDataLength = binaryReader.Read(data, 0, data.Length);
string stringData = Encoding.ASCII.GetString(data, 0, receivedDataLength);
// Write incoming information to console
Console.WriteLine("Client: " + stringData);
// Respond to client
byte[] respondData = Encoding.ASCII.GetBytes("respond");
Array.Resize(ref respondData, 16); // Resizing to 16 byte, because in this example all messages have 16 byte to make it easier to understand.
binaryWriter.Write(respondData, 0, 16);
}
}
}
Client:
class Client
{
private static void Main(string[] args)
{
Console.WriteLine("Press any key to start Client");
while (! Console.KeyAvailable)
{
}
TcpClient client = new TcpClient();
client.Connect("127.0.0.1", 1500);
NetworkStream networkStream = client.GetStream();
// Create BinaryWriter for writing to stream
BinaryWriter binaryWriter = new BinaryWriter(networkStream);
// Creating BinaryReader for reading the stream
BinaryReader binaryReader = new BinaryReader(networkStream);
// Writing "test" to stream
byte[] writeData = Encoding.ASCII.GetBytes("test");
Array.Resize(ref writeData, 16); // Resizing to 16 byte, because in this example all messages have 16 byte to make it easier to understand.
binaryWriter.Write(writeData, 0, 16);
// Reading response and writing it to console
byte[] responeBytes = new byte[16];
binaryReader.Read(responeBytes, 0, 16);
string response = Encoding.ASCII.GetString(responeBytes);
Console.WriteLine("Server: " + response);
while (true)
{
}
}
}
I hope this helps! ;)

You can perform both Read and Write on the same stream.
After you send all the data over, just call stream.Read as in
using (var stream = client.GetStream())
{
stream.Write(data, 0, data.Length);
stream.Flush();
Console.WriteLine("Data sent.");
stream.Read(....); //added sync read here
}
MSDN documentation on TcpClient has an example as well http://msdn.microsoft.com/en-us/library/system.net.sockets.tcpclient.aspx
If you want feed back such as reporting # of bytes received so far, you'll have to use async methods.

Here's an example of what (I think) you want to do:
static void Main(string[] args) {
var server = new Task(Server);
server.Start();
System.Threading.Thread.Sleep(10); // give server thread a chance to setup
try {
TcpClient client = new TcpClient();
client.Connect("127.0.0.1", 1500);
Console.WriteLine("Connected.");
var data = new byte[100];
var hello = ASCIIEncoding.ASCII.GetBytes("Hello");
Console.WriteLine("Sending data.....");
using (var stream = client.GetStream()) {
stream.Write(hello, 0, hello.Length);
stream.Flush();
Console.WriteLine("Data sent.");
// You could then read data from server here:
var returned = stream.Read(data, 0, data.Length);
var rec = new String(ASCIIEncoding.ASCII.GetChars(data, 0, data.Length));
rec = rec.TrimEnd('\0');
if (rec == "How are you?") {
var fine = ASCIIEncoding.ASCII.GetBytes("fine and you?");
stream.Write(fine, 0, fine.Length);
}
}
client.Close();
Console.ReadLine();
}
catch (Exception e) {
Console.WriteLine("Error: " + e.StackTrace);
Console.ReadLine();
}
}
public static void Server() {
try {
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
Console.WriteLine("*Starting TCP listener...");
TcpListener listener = new TcpListener(ipAddress, 1500); // generally use ports > 1024
listener.Start();
Console.WriteLine("*Server is listening on " + listener.LocalEndpoint);
Console.WriteLine("*Waiting for a connection...");
while (true) {
Socket client = listener.AcceptSocket();
while (client.Connected) {
Console.WriteLine("*Connection accepted.");
Console.WriteLine("*Reading data...");
byte[] data = new byte[100];
int size = client.Receive(data);
Console.WriteLine("*Recieved data: ");
var rec = new String(ASCIIEncoding.ASCII.GetChars(data, 0, size));
rec = rec.TrimEnd('\0');
Console.WriteLine(rec);
if (client.Connected == false) {
client.Close();
break;
}
// you would write something back to the client here
if (rec == "Hello") {
client.Send(ASCIIEncoding.ASCII.GetBytes("How are you?"));
}
if (rec == "fine and you?") {
client.Disconnect(false);
}
}
}
listener.Stop();
}
catch (Exception e) {
Console.WriteLine("Error: " + e.StackTrace);
Console.ReadLine();
}
}
}
Keep in mind that data sent via sockets can arrive fragmented (in different packets). This doesn't usually happen with the packets are small.

Socket Connecting and Sending Data Received but not read on ASP.net side from Android

Hi i'm having an issue with sending a tcp socket from my android device to my Asp.net application on my PC
The problem seems to be with that ASP.net code as i get 5 bytes received but not managing to read them.
try
{
listener = new TcpListener(serverPort);
listener.Start();
}catch(SocketException se)
{
string s = se.Message;
Environment.Exit(se.ErrorCode);
}
byte[] rcvBuffer = new byte[5000000];
int bytesRcvd;
int buffersize = 1024;
for(;;)
{
TcpClient client = null;
NetworkStream netStream = null;
try
{
client = listener.AcceptTcpClient();
netStream = client.GetStream();
byte[] data = new byte[client.ReceiveBufferSize];
bytesRcvd = netStream.Read(rcvBuffer, 0, rcvBuffer.Length);
int totalBytesEchoed = 0;
while ( bytesRcvd > 0)
{
int nextPacket = (bytesRcvd > buffersize) ? buffersize : bytesRcvd;
int bytes = netStream.Read(rcvBuffer, 0, bytesRcvd);
totalBytesEchoed += bytesRcvd;
string s = Encoding.ASCII.GetString(data, 0, bytes);
}
netStream.Close();
client.Close();
}
catch(Exception e)
{
netStream.Close();
}
}
}

The Read() call on the netStream fills the data into the rcvBuffer, but then you try to get your string from the data buffer...
and you read two times before you try to get the string, once before the while and once inside the while. Maybe you can use a do{}while() loop.

how can i send Full name in TCP service in 2nd time?

When i send data through TCP server to client first time full name retrieved when i again send the another name like book it retrieved as (ook) in C sharp
client side code
sck = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
while (true)
{
IPEndPoint localEndPoint;
localEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.2"), 1);
try
{
sck.Connect(localEndPoint);
}
catch
{
Console.Write("Unable to connect to remote end point!\r\n");
);
}
Console.Write("Enter Text: ");
string text = Console.ReadLine();
byte[] data = Encoding.ASCII.GetBytes(text);
sck.Send(data);
Console.Write("Data Sent!\r\n");
sck.Close();
Console.ReadLine();
Server Side Code
while (true)
{
Socket accepted = sck.Accept();
Buffer = new byte[accepted.SendBufferSize];
int bytesRead = accepted.Receive(Buffer);
byte[] formatted = new byte[bytesRead];
for (int i = 0; i < bytesRead; i++)
{
formatted[i] = Buffer[i];
//Console.WriteLine(Buffer[i] + "\r\n");
}
//string strData = Encoding.ASCII.GetString(Buffer);
string strData = Encoding.ASCII.GetString(formatted);
Console.Write(strData + "\r\n");
accepted.Close();
}

There is something which I don't understand, you use Buffer as a variable but that is a type in C#, I don't know where and how you declare it.
Anyway, I would do it like this:
while (true)
{
Socket accepted = sck.Accept();
byte[] buffer = new byte[1024];
int ret=0;
StringBuilder sb= new StringBuilder();
while ((ret=accepted.Receive(buffer)) > 0)
{
sb.Append(Encoding.ASCII.GetString(buffer, 0, ret));
}
Console.Write(sb.ToString() + "\r\n");
accepted.Close();
}
In order to keep a dialog between both sockets you need something called a protocol, which means you know when you have received the whole data then you reply to the sender. A protocol could be: send a packet which inform what you are going to send, length of the message mainly. Other way is to stop reading when something comes into the message, for example the string "#END#" the return character '\r', etc. If you only want to send one single message and received back a reply message one thing you can do, however, is to shutdown the client part, only the send part Socket.Shutdown(SocketShutdown.Send);, with that, the sender tells the receiver it has sent all data, the receiver receives that signal and then it can send a reply message to the sender.
The client:
sck.Send(data);
Console.Write("Data Sent!\r\n");
// tell the server we have done sending data.
sck.Shutdown(SocketShutdown.Send);
// Now receive from the server
byte[] buffer = new byte[1024];
int ret = 0;
StringBuilder sb = new StringBuilder();
while ((ret = sck.Receive(buffer)) > 0)
{
sb.Append(Encoding.ASCII.GetString(buffer, 0, ret));
}
Console.Write(sb.ToString() + "\r\n");
sck.Close();
The server
while (true)
{
Socket accepted = sck.Accept();
byte[] buffer = new byte[1024];
int ret=0;
StringBuilder sb= new StringBuilder();
while ((ret=accepted.Receive(buffer)) > 0)
{
sb.Append(Encoding.ASCII.GetString(buffer, 0, ret));
}
Console.Write(sb.ToString() + "\r\n");
byte[] reply = Encoding.ASCII.GetBytes("I've got it!");
accepted.Send(reply);
accepted.Close();
}