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length header suddenly has wrong value when use read int32?

I wrote a tcp listener to receive a sequence of images from single client , this is the code of server :
new Thread(() =>
{
while (true)
{
displayingFrame.Start(); // another thread to display images
Socket socket = listener.AcceptSocket();
TcpClient client = new TcpClient();
client.Client = socket;
Debug.WriteLine("Connection accepted.");
var childSocketThread = new Thread(() =>
{
NetworkStream ns = client.GetStream();
BinaryReader br = new BinaryReader(ns);
while (true)
{
using (MemoryStream ms = new MemoryStream())
{
int length = br.ReadInt32();
Debug.WriteLine("length : " + length);
byte[] buf = new byte[1024];
int totalReaded = 0;
int readed = 0;
while (totalReaded < length)
{
readed = br.Read(buf, 0, buf.Length);
ms.Write(buf, 0, readed);
totalReaded += readed;
}
byte[] frame = ms.ToArray();
this.frames.Enqueue(frame);
Debug.WriteLine("frame enqueued with length " + frame.Length);
}
}
});
childSocketThread.Start();
}
}).Start();
it receive frames very well but suddenly br.ReadInt32(); returns a very big length so br.Read(buf, 0, buf.Length); takes a very long time writing to memory stream and it writes a wrong data inside frame .
this is the client :
TcpClient client = new TcpClient();
client.Connect(new IPEndPoint(IPAddress.Loopback, 20000));
NetworkStream ns = client.GetStream();
BinaryWriter bw = new BinaryWriter(ns);
while ( true )
{
byte[] frame = Screenshot();
bw.Write(frame.Length);
Console.WriteLine("a frame length has flushed : " + frame.Length);
bw.Write(frame);
Console.WriteLine("a frame itself has flushed");
}
Console.ReadKey();
and here the debug info :

If you check the hex value you're getting - 1196314761 - you'll get 0x474E5089 and finally convert to ASCII you will get GNP\x89 which gives us the known magic value \x89PNG that is the marker of PNG file. You're actually reading the content of your screenshot as the length.
Make sure that you're code for reading the data does not read too much from the previous frame. I think you code for reading the data does not include the fact that you might get content of 2 frames in one .Read but then later you just don't care if you have too much data. You only check if it's not less than length.

How to make sure that stream is read completely?

I am using Network Stream, TcpListener and Sockets.
I want to make sure that all the data from sender is received by receiver.
I have below code for receiver
private void StartReciever()
{
util.LoadSettings();
string tcpIpAddress = util.svrSettings["IpAddress"];
string port = util.svrSettings["Port"];
string outDir = util.svrSettings["isOutput"];
new Thread(
() =>
{
if (!File.Exists(util.settingFile))
Logger("Please setup the services first.");
else
{
try
{
IPAddress ipAddress = IPAddress.Parse(tcpIpAddress);
TcpListener tcpListener = new TcpListener(ipAddress, Convert.ToInt32(port));
tcpListener.Start();
Logger("\nWaiting for a client to connect...");
//blocks until a client connects
Socket socketForClient = tcpListener.AcceptSocket();
Logger("\nClient connected");
//Read data sent from client
NetworkStream networkStream = new NetworkStream(socketForClient);
int bytesReceived, totalReceived = 0;
string fileName = "testing.txt";
byte[] receivedData = new byte[10000];
do
{
bytesReceived = networkStream.Read
(receivedData, 0, receivedData.Length);
totalReceived += bytesReceived;
Logger("Progress of bytes recieved: " + totalReceived.ToString());
if (!File.Exists(fileName))
{
using (File.Create(fileName)) { };
}
using (var stream = new FileStream(fileName, FileMode.Append))
{
stream.Write(receivedData, 0, bytesReceived);
}
}
while (bytesReceived != 0);
Logger("Total bytes read: " + totalReceived.ToString());
socketForClient.Close();
Logger("Client disconnected...");
tcpListener.Stop();
}
catch (Exception ex)
{
// Error : "Only one usage of each socket address (protocol/network address/port) is normally permitted"
Logger("There is some error: " + ex.Message);
}
}
}).Start();
}
How can I make sure that my code after do-while loop executes ?
Sender Code:
private static void SendData(string tcpIpAddress, string port, string filename)
{
new Thread(
() =>
{
TcpClient tcpClient = new TcpClient(tcpIpAddress, Convert.ToInt32(port));
//const int bufsize = 8192;
const int bufsize = 10000;
var buffer = new byte[bufsize];
NetworkStream networkStream = tcpClient.GetStream();
using (var readFile = File.OpenRead(filename))
{
int actuallyRead;
while ((actuallyRead = readFile.Read(buffer, 0, bufsize)) > 0)
{
networkStream.Write(buffer, 0, actuallyRead);
}
}
}).Start();
}

How can I make sure that my code after do-while loop executes?
Here, it's easy because you can close the connection on the sender which will cause the receiver to read zero bytes and terminate the loop.
In fact you forgot to clean up the sender. Dispose of all resources. This fixes the problem.
Your code would benefit from the Code Review SE. I see about a dozen issues immaterial to this question. Would be a great way for you to improve yourself.
For example you can replace the copy loops with Stream.Copy.

The usual way I've seen this done to prepend the data being sent with the number of bytes about to be sent. That way the receiver knows that the packet has been read. Even if the network gets interrupted or the sender sends something else without a break.
Note that doing this you can also read the first 8 bytes (or 4 if an Int32 will do the job) before allocating the read buffer which can help optimise the buffer size
Another common way of doing it is with a specific terminator, but then you have to guarantee that whatever you're sending cannot contain that terminator

C# sockets: can't read after writing to socket

In my client/server application my client wiil communicate with the server for 2 functions: the client will either request data from the server or it will send data so the server will save it. I'm using one socket for both methods, and the method to be used is defined by the first byte sent. If the first byte is "1" it is requesting data. If it is "2", it will send data (data bytes are sent after the "2" byte). It works perfectly for sending data. But when I'm requesting data it works, as long as I don't read the socket stream in the client. It's like if I make the client read data after sending data, the server will have no data to read, and it just crashes when trying to read the data.
Here is my server code:
private const int BufferSize = 1024;
NetworkStream netstream = null;
byte[] RecData = new byte[BufferSize];
int RecBytes;
try {
netstream = clientSocket.GetStream();
int totalrecbytes = 0;
using (MemoryStream ms = new MemoryStream()) {
//When I get here, there is no data to read
while ((RecBytes = netstream.Read(RecData, 0, RecData.Length)) > 0) {
ms.Write(RecData, 0, RecBytes);
totalrecbytes += RecBytes;
}
byte[] bytes = ms.ToArray();
byte b = bytes[0];
switch (b) {
case 1:
//Here I gather data and put it in "stream" variable
byte[] SendingBuffer = null;
int NoOfPackets = Convert.ToInt32(Math.Ceiling(Convert.ToDouble(stream.Length) / Convert.ToDouble(BufferSize)));
int TotalLength = (int)stream.Length, CurrentPacketLength, counter = 0;
for (int i = 0; i < NoOfPackets; i++) {
if (TotalLength > BufferSize) {
CurrentPacketLength = BufferSize;
TotalLength = TotalLength - CurrentPacketLength;
}
else
CurrentPacketLength = TotalLength;
SendingBuffer = new byte[CurrentPacketLength];
stream.Read(SendingBuffer, 0, CurrentPacketLength);
netstream.Write(SendingBuffer, 0, (int)SendingBuffer.Length);
}
netstream.Flush();
}
catch (Exception e) {
Console.WriteLine("EXCEPTION:\n" + e.ToString());
}
break;
case 2:
//Code to read data
break;
}
}
netstream.Close()
clientSocket.Close();
And here is my client code:
using (System.Net.Sockets.TcpClient clientSocket = new System.Net.Sockets.TcpClient()) {
string returnData = "";
IAsyncResult ar = clientSocket.BeginConnect("127.0.0.1", 8080, null, null);
System.Threading.WaitHandle wh = ar.AsyncWaitHandle;
try {
if (!ar.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(5), false)) {
clientSocket.Close();
Console.WriteLine("Timeout");
return;
}
System.Net.Sockets.NetworkStream serverStream = clientSocket.GetStream();
byte b = 1;
byte[] outStream = { b };
serverStream.Write(outStream, 0, outStream.Length);
serverStream.Flush();
//If I comment following lines, the server can read sent data, but server can't otherwise
byte[] RecData = new byte[1024];
int RecBytes;
int totalrecbytes = 0;
MemoryStream MS = new MemoryStream();
while ((RecBytes = serverStream.Read(RecData, 0, RecData.Length)) > 0) {
MS.Write(RecData, 0, RecBytes);
totalrecbytes += RecBytes;
}
serverStream.Close();
clientSocket.Close();
clientSocket.EndConnect(ar);
}
catch (Exception ex) {
Console.WriteLine("Exceção: " + ex.ToString());
}
finally {
wh.Close();
}
}
So, how can I send data to server and read the response? (I tried even putting the thread to sleep after sending data, with no luck.)
Thanks in advance.
EDIT:
With some debug messages I discovered that the server do read the "1" byte that was sent, but somehow it gets stuck inside the while loop, like, the server just stops there, no more loops and it does not leave the while loop. I saw that after writing "loop" in console inside the while loop, and writing read bytes also in console. It wrote "loop" once, and the read byte.

This code worries me:
//When I get here, there is no data to read
while ((RecBytes = netstream.Read(RecData, 0, RecData.Length)) > 0) {
ms.Write(RecData, 0, RecBytes);
totalrecbytes += RecBytes;
}
You are reading until the client closes the connection (or shuts down sending, which you don't do). But the client only closes when the server has replied. The server reply will never come. It is a deadlock.
Solution: Read a single byte to determine the requests command (b).
Unrelated to the question, your "packetised" sending (NoOfPackets, ...) does not seem to serve any purpose. Just use Stream.Copy to write. TCP does not have packets.
An even better solution would be to abandon your custom TCP protocol and use an HTTP library. All these concerns just go away. There are various smaller problems with your code that are very typical to see in TCP code.

create a "listener" for an incoming socket stream that will contain a byte[] array

I'm creating a socket server that needs to continuously listen for incoming messages from the connected clients. Those messages will be sent in a byte[] array. I had the server working great with a StreamReader but StreamReader only works with textual represenations of the data being sent...not byte[] arrays.
Here's what I had:
StreamReader reader = new StreamReader(Client.GetStream());
string line = "";
while (true)
{
line = reader.ReadLine();
if (!string.IsNullOrEmpty(line))
{
parentForm.ApplyText(line + "\r\n");
SocketServer.SendBroadcast(line);
}
}
I need to now convert that into a raw stream somehow that will convert the stream contents into a byte[] array but I can't seem to get a handle on it.
I tried this:
while (true)
{
var bytes = default(byte[]);
using (var memstream = new MemoryStream())
{
var buffer = new byte[512];
var bytesRead = default(int);
while ((bytesRead = reader.BaseStream.Read(buffer, 0, buffer.Length)) > 0)
memstream.Write(buffer, 0, bytesRead);
bytes = memstream.ToArray();
}
//parentForm.ApplyText(bytes.Length + "\r\n");
}
but as you might guess, the while(true) loop doesn't quite work how I need it to. Can anyone help me with some code adjustment to make this work as I need it to. It needs to continuously listen for incoming messages, then when a message is received, it needs to do something with that message (the byte[] array) then go back to listening again.
TIA

I guess "listening continuously" is not task of reader its a task of listener. I ran into same problem when i was writing server using TcpListener. I am not sure what you want to do but i am posting solution for your "listening continuous" and reading into byte[] problem. I guess this code might help you:
TcpListener t = new TcpListener(IPAddress.Loopback, _port);
t.Start();
Console.WriteLine("Server is started and waiting for client\n\n");
byte[] buff = new byte[255];
NetworkStream stream;
TcpClient client;
while(true)
{
client = t.AcceptTcpClient();
if (!client.Connected)
return;
stream = client.GetStream();
while ((stream.Read(buff, 0, buff.Length)) != 0)
{
break;
}
if (0 != buff.Length)
break;
}

There's no need to convert anything. GetStream() returns a NetworkStream. See the sample Microsoft includes in the NetworkStream.Read Method. All you have to do is replace the myCompleteMessage.AppendFormat("{0}", Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead)); line with an appropriate storage mechanism.

Ensure streamreader doesn't hang waiting for data

The code below reads everything there is to read from tcp client stream, and on the next iteration it will just sit there on the Read() (i'm assuming waiting for data). How can I ensure it doesn't and just returns when there's nothing there to read? Do I have to set low timeout, and respond to an exception when it fails out? Or there's a better way?
TcpClient tcpclnt = new TcpClient();
tcpclnt.Connect(ip, port);
Stream stm = tcpclnt.GetStream();
stm.Write(cmdBuffer, 0, cmdBuffer.Length);
byte[] response = new Byte[2048];
MemoryStream ms = new MemoryStream();
byte[] buffer = new Byte[2048];
int length;
while ((length = stm.Read(buffer, 0, buffer.Length)) > 0)
ms.Write(buffer, 0, length);
byte[] response = ms.ToArray();
tcpclnt.Close();

TcpClient has two properties that I would play with.
NoDelay Gets or sets a value that disables a delay when send or receive buffers are not full.
ReceiveTimeout Gets or sets the amount of time a TcpClient will wait to receive data once a read operation is initiated

Maybe you should use multithreading. One thread should wait for data, another should process received data.

Does the server have "Keep Connections Alive" on ?
I have had servers which will send you a stream of empty bytes as long as you request them.
Turning "Keep Connections Alive" stopped it doing this.

var socket = new System.Net.Sockets.TcpClient();
socket.NoDelay = true;
socket.Connect(uri.Host, port);
var ns = socket.GetStream();
int timeout = 500; //ms
DateTime lastReceived = DateTime.Now;
string buffer = "";
while (true)
{
if (ns.DataAvailable)
{
var b = ns.ReadByte();
buffer += b + ", "; //customise this line yourself
lastReceived = DateTime.Now;
continue;
}
if (lastReceived.AddMilliseconds(timeout) < DateTime.Now) break;
System.Threading.Thread.Sleep(timeout / 5);
}