Develop Reference

Send and Receive large amount of data through tcp stream using read/write (Error)

I am trying to receive data at my server of any length through tcp connection. First my client sends length of data to server through stream.write then it send the actual data.
At Client I receive the length and loop until whole the data is received successfully.
The problem is: "I receive 0 size on the server no matters what the length of data is". I tried to figure out the issue but could not get where the problem is. Any kind of help/hint would be appreciated.
Server Side Code:
byte[] lengthOfData = new byte[2048];
byte[] buffer;
try
{
stream = client.GetStream();
eventLog1.WriteEntry("Size of 1st = "+stream.Read(lengthOfData,0,lengthOfData.Length));
int numBytesToRead = ByteArraySerializer.BytesArrayToInt(lengthOfData);
eventLog1.WriteEntry("number of bytes to read= "+numBytesToRead);
buffer = new byte[numBytesToRead+10];
int numBytesRead = 0;
do
{
int n = stream.Read(buffer, numBytesRead, 10);
numBytesRead += n;
numBytesToRead -= n;
eventLog1.WriteEntry("number of bytes read= " + numBytesRead);
} while (numBytesToRead > 0);
}
catch (Exception e) // Called automatically when Client Diposes or disconnects unexpectedly
{
eventLog1.WriteEntry("Connection Closes: "+e.ToString());
lock (connectedClients)
{
connectedClients.Remove(client);
}
client.Close();
break;
}
Client Side Code
byte[] command = ByteArraySerializer.Serialize<Command>(cmd);
byte[] sizeOfData = ByteArraySerializer.IntToBytesArray(command.Length);
stream.Write(sizeOfData, 0, sizeOfData.Length);
Console.WriteLine("Size of Data = "+command.Length);
stream.Write(command, 0, command.Length);

Change the following line at server
byte[] lengthOfData = new byte[2048];
to
byte[] lengthOfData = new byte[sizeof(int)];
The issue was that the read at server was supposed to read only 4 bytes integer whereas it was reading other data as well which was getting written after writing the length of data. We are supposed to read only 4 bytes if we want to get the length of data(integer).

How to get all data from NetworkStream

I am trying to read all data present in the buffer of the Machine connected through TCP/IP but i don't know why i am not getting all data ,some data is getting Missed.
Here is the code that i am using ..
using (NetworkStream stream = client.GetStream())
{
byte[] data = new byte[1024];
int numBytesRead = stream.Read(data, 0, data.Length);
if (numBytesRead > 0)
{
string str= Encoding.ASCII.GetString(data, 0, numBytesRead);
}
}
Please tell me what i am missing to get all the data from the machine.
Thanks in advance..

The problem with your code is that you will not get all the data if the data size is bigger than the buffer size (1024 bytes in your case) so you have to Read the stream inside the loop. Then you can Write all the data inside a MemoryStream until the end of the NetworkStream.
string str;
using (NetworkStream stream = client.GetStream())
{
byte[] data = new byte[1024];
using (MemoryStream ms = new MemoryStream())
{
int numBytesRead ;
while ((numBytesRead = stream.Read(data, 0, data.Length)) > 0)
{
ms.Write(data, 0, numBytesRead);
}
str = Encoding.ASCII.GetString(ms.ToArray(), 0, (int)ms.Length);
}
}

This example from MSDN: NetworkStream.DataAvailable shows how you can use that property to do so:
// Examples for CanRead, Read, and DataAvailable.
// Check to see if this NetworkStream is readable.
if(myNetworkStream.CanRead)
{
byte[] myReadBuffer = new byte[1024];
StringBuilder myCompleteMessage = new StringBuilder();
int numberOfBytesRead = 0;
// Incoming message may be larger than the buffer size.
do{
numberOfBytesRead = myNetworkStream.Read(myReadBuffer, 0, myReadBuffer.Length);
myCompleteMessage.AppendFormat("{0}", Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead));
}
while(myNetworkStream.DataAvailable);
// Print out the received message to the console.
Console.WriteLine("You received the following message : " +
myCompleteMessage);
}
else
{
Console.WriteLine("Sorry. You cannot read from this NetworkStream.");
}

Try this:
private string GetResponse(NetworkStream stream)
{
byte[] data = new byte[1024];
using (MemoryStream memoryStream = new MemoryStream())
{
do
{
stream.Read(data, 0, data.Length);
memoryStream.Write(data, 0, data.Length);
} while (stream.DataAvailable);
return Encoding.ASCII.GetString(memoryStream.ToArray(), 0, (int)memoryStream.Length);
}
}

Try this code:
using (NetworkStream stream = client.GetStream())
{
while (!stream.DataAvailable)
{
Thread.Sleep(20);
}
if (stream.DataAvailable && stream.CanRead)
{
Byte[] data = new Byte[1024];
List<byte> allData = new List<byte>();
do
{
int numBytesRead = stream.Read(data,0,data.Length);
if (numBytesRead == data.Length)
{
allData.AddRange(data);
}
else if (numBytesRead > 0)
{
allData.AddRange(data.Take(numBytesRead));
}
} while (stream.DataAvailable);
}
}
Hope this helps, it should prevent that you miss any data sended to you.

The synchronous method sometimes does not display the request body. Using the asynchronous method stably displays request body.
string request = default(string);
StringBuilder sb = new StringBuilder();
byte[] buffer = new byte[client.ReceiveBufferSize];
int bytesCount;
if (client.GetStream().CanRead)
{
do
{
bytesCount = client.GetStream().ReadAsync(buffer, 0, buffer.Length).Result;
sb.Append(Encoding.UTF8.GetString(buffer, 0, bytesCount));
}
while(client.GetStream().DataAvailable);
request = sb.ToString();
}

TCP itself does not have any ways to define "end of data" condition. This is responsibility of application level portocol.
For instance see HTTP request description:
A client request (consisting in this case of the request line and only one header field) is followed by a blank line, so that the request ends with a double newline
So, for request end of data is determined by two newline sequences. And for response:
Content-Type specifies the Internet media type of the data conveyed by the HTTP message, while Content-Length indicates its length in bytes.
The response content size is specified in header before data.
So, it's up to you how to encode amount of data transferred at once - it can be just first 2 or 4 bytes in the beginning of the data holding total size to read or more complex ways if needed.

for my scenario, the message itself was telling the length of subsequent message. here is the code
int lengthOfMessage=1024;
string message = "";
using (MemoryStream ms = new MemoryStream())
{
int numBytesRead;
while ((numBytesRead = memStream.Read(MessageBytes, 0, lengthOfMessage)) > 0)
{
lengthOfMessage = lengthOfMessage - numBytesRead;
ms.Write(MessageBytes, 0, numBytesRead);
}
message = Encoding.ASCII.GetString(ms.ToArray(), 0, (int)ms.Length);
}

#George Chondrompilas answer is correct but instead of writing it by yourself you can use CopyTo function which does the same :
https://stackoverflow.com/a/65188160/4120180

Sending and receiving compressed data over a TCP socket

Need help with sending and receiving compressed data over TCP socket.
The code works perfectly fine if I don't use compression, but something very strange happens when I do use compression.. Basically, the problem is that the stream.Read() operation gets skipped and I don't know why..
My code:
using (var client = new TcpClient())
{
client.Connect("xxx.xxx.xx.xx", 6100);
using (var stream = client.GetStream())
{
// SEND REQUEST
byte[] bytesSent = Encoding.UTF8.GetBytes(xml);
// send compressed bytes (if this is used, then stream.Read() below doesn't work.
//var compressedBytes = bytesSent.ToStream().GZipCompress();
//stream.Write(compressedBytes, 0, compressedBytes.Length);
// send normal bytes (uncompressed)
stream.Write(bytesSent, 0, bytesSent.Length);
// GET RESPONSE
byte[] bytesReceived = new byte[client.ReceiveBufferSize];
// PROBLEM HERE: when using compression, this line just gets skipped over very quickly
stream.Read(bytesReceived, 0, client.ReceiveBufferSize);
//var decompressedBytes = bytesReceived.ToStream().GZipDecompress();
//string response = Encoding.UTF8.GetString(decompressedBytes);
string response = Encoding.UTF8.GetString(bytesReceived);
Console.WriteLine(response);
}
}
You will notice some extension methods above. Here is the code in case you are wondering if something is wrong there.
public static MemoryStream ToStream(this byte[] bytes)
{
return new MemoryStream(bytes);
}
public static byte[] GZipCompress(this Stream stream)
{
using (var memoryStream = new MemoryStream())
{
using (var gZipStream = new GZipStream(memoryStream, CompressionMode.Compress))
{
stream.CopyTo(gZipStream);
}
return memoryStream.ToArray();
}
}
public static byte[] GZipDecompress(this Stream stream)
{
using (var memoryStream = new MemoryStream())
{
using (var gZipStream = new GZipStream(stream, CompressionMode.Decompress))
{
gZipStream.CopyTo(memoryStream);
}
return memoryStream.ToArray();
}
}
The extensions work quite well in the following, so I'm sure they're not the problem:
string original = "the quick brown fox jumped over the lazy dog";
byte[] compressedBytes = Encoding.UTF8.GetBytes(original).ToStream().GZipCompress();
byte[] decompressedBytes = compressedBytes.ToStream().GZipDecompress();
string result = Encoding.UTF8.GetString(decompressedBytes);
Console.WriteLine(result);
Does anyone have any idea why the Read() operation is being skipped when the bytes being sent are compressed?
EDIT
I received a message from the API provider after showing them the above sample code. They had this to say:
at a first glance I guess the header is missing. The input must start
with a 'c' followed by the length of the input
(sprintf(cLength,"c%09d",hres) in our example). We need this because
we can't read until we find a binary 0 to recognize the end.
They previously provided some sample code in C, which I don't fully understand 100%, as follows:
example in C:
#include <zlib.h>
uLongf hres;
char cLength[COMPRESS_HEADER_LEN + 1] = {'\0'};
n = read(socket,buffer,10);
// check if input is compressed
if(msg[0]=='c') {
compressed = 1;
}
n = atoi(msg+1);
read.....
hres = 64000;
res = uncompress((Bytef *)msg, &hres, (const Bytef*)
buffer/*compressed*/, n);
if(res == Z_OK && hres > 0 ){
msg[hres]=0; //original
}
else // errorhandling
hres = 64000;
if (compressed){
res = compress((Bytef *)buffer, &hres, (const Bytef *)msg, strlen(msg));
if(res == Z_OK && hres > 0 ) {
sprintf(cLength,"c%09d",hres);
write(socket,cLength,10);
write(socket, buffer, hres);
}
else // errorhandling
makefile: add "-lz" to the libs
They're using zlib. I don't suspect that to make any difference, but I did try using zlib.net and I still get no response anyway.
Can someone give me an example of how exactly I'm supposed to send this input length in C#?
EDIT 2
In response to #quantdev, here is what I am trying now for the length prefix:
using (var client = new TcpClient())
{
client.Connect("xxx.xxx.xx.xx", 6100);
using (var stream = client.GetStream())
{
// SEND REQUEST
byte[] bytes = Encoding.UTF8.GetBytes(xml);
byte[] compressedBytes = ZLibCompressor.Compress(bytes);
byte[] prefix = Encoding.UTF8.GetBytes("c" + compressedBytes.Length);
byte[] bytesToSend = new byte[prefix.Length + compressedBytes.Length];
Array.Copy(prefix, bytesToSend, prefix.Length);
Array.Copy(compressedBytes, 0, bytesToSend, prefix.Length, compressedBytes.Length);
stream.Write(bytesToSend, 0, bytesToSend.Length);
// WAIT
while (client.Available == 0)
{
Thread.Sleep(1000);
}
// GET RESPONSE
byte[] bytesReceived = new byte[client.ReceiveBufferSize];
stream.Read(bytesReceived, 0, client.ReceiveBufferSize);
byte[] decompressedBytes = ZLibCompressor.DeCompress(bytesReceived);
string response = Encoding.UTF8.GetString(decompressedBytes);
Console.WriteLine(response);
}
}

You need to check the return value of the Read() calls you are making on the TCP stream: it is the number of bytes effectively read.
MSDN says :
Return Value
The total number of bytes read into the buffer. This can be less than the number of bytes requested if that many bytes are not
currently available, or zero (0) if the end of the stream has been
reached.
If the socket is closed, the call will return immediately 0 (which is what might be happening here).
If is not 0, then you must check how many bytes you did actually received, if it is less than client.ReceiveBufferSize, you will need additional calls to Read to retrieve the remaining bytes.
Prior to you call to read, check that some data is actually available on the socket :
while(client.Available == 0)
// wait ...
http://msdn.microsoft.com/en-us/library/system.net.sockets.tcpclient.available%28v=vs.110%29.aspx

I think you may have the end of file or so. Can you try setting the stream position before reading the stream
stream.position = 0;
http://msdn.microsoft.com/en-us/library/vstudio/system.io.stream.read

Encoding.UTF8.GetString shouldn't be used on arbitrary byte array.
e.g.: The compressed bytes may contain NULL character, which is not allowed in UTF-8 encoded text except for being used as terminator.
If you want to print the received bytes for debugging, maybe you should just print them as integers.

Only Getting Half a Barcode from TCP/IP Barcode Reader

I have a Microscan TCP/IP barcode reader. I am currently using the following code to connect to it and retrieve a barcode when read:
// responseData string will be the barcode received from reader
string responseData = null;
TcpClient client = new TcpClient("10.90.10.36", 2001);
// The "getData" is just a generic string to initiate connection
Byte[] sentData = System.Text.Encoding.ASCII.GetBytes("getData");
NetworkStream stream = client.GetStream();
stream.Write(sentData, 0, sentData.Length);
Byte[] receivedData = new Byte[20];
Int32 bytes = stream.Read(receivedData, 0, receivedData.Length);
for (int i = 0; i < bytes; i++)
{
responseData += Convert.ToChar(receivedData[i]);
}
// Closes the socket connection.
client.Close();
The issue that I am having is that I am only getting 10 characters when the barcode is 15. Everything works correctly until the Int32 bytes = stream.Read(receivedData, 0 receivedData.Length); line. The Read call is returning 10 rather than 15 as it should be. I have tried modifying the code in a few different ways, but all of them have just returned 10 characters like normal. This works correctly if the barcode is 10 characters or fewer, but not if more.
I don't think it's an issue with the scanner, but I am checking into that as well. Anyone have any ideas?

Try something like:
// responseData string will be the barcode received from reader
string responseData = null;
using (TcpClient client = new TcpClient("10.90.10.36", 2001))
{
using (NetworkStream stream = client.GetStream())
{
byte[] sentData = System.Text.Encoding.ASCII.GetBytes("getData");
stream.Write(sentData, 0, sentData.Length);
byte[] buffer = new byte[32];
int bytes;
while ((bytes = stream.Read(buffer, 0, buffer.Length)) != 0)
{
for (int i = 0; i < bytes; i++)
{
responseData += (char)buffer[i];
}
}
}
}
The while cycle will repeat itself while there are new characters that can be received. I have even put some using around your code (it's better to use them instead of Closeing manually objects)

What is the correct way to read from NetworkStream in .NET

I've been struggling with this and can't find a reason why my code is failing to properly read from a TCP server I've also written. I'm using the TcpClient class and its GetStream() method but something is not working as expected. Either the operation blocks indefinitely (the last read operation doesn't timeout as expected), or the data is cropped (for some reason a Read operation returns 0 and exits the loop, perhaps the server is not responding fast enough). These are three attempts at implementing this function:
// this will break from the loop without getting the entire 4804 bytes from the server
string SendCmd(string cmd, string ip, int port)
{
var client = new TcpClient(ip, port);
var data = Encoding.GetEncoding(1252).GetBytes(cmd);
var stm = client.GetStream();
stm.Write(data, 0, data.Length);
byte[] resp = new byte[2048];
var memStream = new MemoryStream();
int bytes = stm.Read(resp, 0, resp.Length);
while (bytes > 0)
{
memStream.Write(resp, 0, bytes);
bytes = 0;
if (stm.DataAvailable)
bytes = stm.Read(resp, 0, resp.Length);
}
return Encoding.GetEncoding(1252).GetString(memStream.ToArray());
}
// this will block forever. It reads everything but freezes when data is exhausted
string SendCmd(string cmd, string ip, int port)
{
var client = new TcpClient(ip, port);
var data = Encoding.GetEncoding(1252).GetBytes(cmd);
var stm = client.GetStream();
stm.Write(data, 0, data.Length);
byte[] resp = new byte[2048];
var memStream = new MemoryStream();
int bytes = stm.Read(resp, 0, resp.Length);
while (bytes > 0)
{
memStream.Write(resp, 0, bytes);
bytes = stm.Read(resp, 0, resp.Length);
}
return Encoding.GetEncoding(1252).GetString(memStream.ToArray());
}
// inserting a sleep inside the loop will make everything work perfectly
string SendCmd(string cmd, string ip, int port)
{
var client = new TcpClient(ip, port);
var data = Encoding.GetEncoding(1252).GetBytes(cmd);
var stm = client.GetStream();
stm.Write(data, 0, data.Length);
byte[] resp = new byte[2048];
var memStream = new MemoryStream();
int bytes = stm.Read(resp, 0, resp.Length);
while (bytes > 0)
{
memStream.Write(resp, 0, bytes);
Thread.Sleep(20);
bytes = 0;
if (stm.DataAvailable)
bytes = stm.Read(resp, 0, resp.Length);
}
return Encoding.GetEncoding(1252).GetString(memStream.ToArray());
}
The last one "works", but it certainly looks ugly to put a hard-coded sleep inside the loop considering that sockets already support read timeouts! Do I need to setup some property(ies) on the TcpClient of the NetworkStream? Does the problem resides in the server? The server don't close the connections, it is up to the client to do so. The above is also running inside the UI thread context (test program), maybe it has something to do with that...
Does someone know how to properly use NetworkStream.Read to read data until no more data is available? I guess what I'm wishing for is something like the old Win32 winsock timeout properties... ReadTimeout, etc. It tries to read until the timeout is reached, and then return 0... But it sometimes seem to return 0 when data should be available (or on the way.. can Read return 0 if is available?) and it then blocks indefinitely on the last read when data is not available...
Yes, I'm at a loss!

Networking code is notoriously difficult to write, test and debug.
You often have lots of things to consider such as:
what "endian" will you use for the data that is exchanged (Intel x86/x64 is based on little-endian) - systems that use big-endian can still read data that is in little-endian (and vice versa), but they have to rearrange the data. When documenting your "protocol" just make it clear which one you are using.
are there any "settings" that have been set on the sockets which can affect how the "stream" behaves (e.g. SO_LINGER) - you might need to turn certain ones on or off if your code is very sensitive
how does congestion in the real world which causes delays in the stream affect your reading/writing logic
If the "message" being exchanged between a client and server (in either direction) can vary in size then often you need to use a strategy in order for that "message" to be exchanged in a reliable manner (aka Protocol).
Here are several different ways to handle the exchange:
have the message size encoded in a header that precedes the data - this could simply be a "number" in the first 2/4/8 bytes sent (dependent on your max message size), or could be a more exotic "header"
use a special "end of message" marker (sentinel), with the real data encoded/escaped if there is the possibility of real data being confused with an "end of marker"
use a timeout....i.e. a certain period of receiving no bytes means there is no more data for the message - however, this can be error prone with short timeouts, which can easily be hit on congested streams.
have a "command" and "data" channel on separate "connections"....this is the approach the FTP protocol uses (the advantage is clear separation of data from commands...at the expense of a 2nd connection)
Each approach has its pros and cons for "correctness".
The code below uses the "timeout" method, as that seems to be the one you want.
See http://msdn.microsoft.com/en-us/library/bk6w7hs8.aspx. You can get access to the NetworkStream on the TCPClient so you can change the ReadTimeout.
string SendCmd(string cmd, string ip, int port)
{
var client = new TcpClient(ip, port);
var data = Encoding.GetEncoding(1252).GetBytes(cmd);
var stm = client.GetStream();
// Set a 250 millisecond timeout for reading (instead of Infinite the default)
stm.ReadTimeout = 250;
stm.Write(data, 0, data.Length);
byte[] resp = new byte[2048];
var memStream = new MemoryStream();
int bytesread = stm.Read(resp, 0, resp.Length);
while (bytesread > 0)
{
memStream.Write(resp, 0, bytesread);
bytesread = stm.Read(resp, 0, resp.Length);
}
return Encoding.GetEncoding(1252).GetString(memStream.ToArray());
}
As a footnote for other variations on this writing network code...when doing a Read where you want to avoid a "block", you can check the DataAvailable flag and then ONLY read what is in the buffer checking the .Length property e.g. stm.Read(resp, 0, stm.Length);

Setting the underlying socket ReceiveTimeout property did the trick. You can access it like this: yourTcpClient.Client.ReceiveTimeout. You can read the docs for more information.
Now the code will only "sleep" as long as needed for some data to arrive in the socket, or it will raise an exception if no data arrives, at the beginning of a read operation, for more than 20ms. I can tweak this timeout if needed. Now I'm not paying the 20ms price in every iteration, I'm only paying it at the last read operation. Since I have the content-length of the message in the first bytes read from the server I can use it to tweak it even more and not try to read if all expected data has been already received.
I find using ReceiveTimeout much easier than implementing asynchronous read... Here is the working code:
string SendCmd(string cmd, string ip, int port)
{
var client = new TcpClient(ip, port);
var data = Encoding.GetEncoding(1252).GetBytes(cmd);
var stm = client.GetStream();
stm.Write(data, 0, data.Length);
byte[] resp = new byte[2048];
var memStream = new MemoryStream();
var bytes = 0;
client.Client.ReceiveTimeout = 20;
do
{
try
{
bytes = stm.Read(resp, 0, resp.Length);
memStream.Write(resp, 0, bytes);
}
catch (IOException ex)
{
// if the ReceiveTimeout is reached an IOException will be raised...
// with an InnerException of type SocketException and ErrorCode 10060
var socketExept = ex.InnerException as SocketException;
if (socketExept == null || socketExept.ErrorCode != 10060)
// if it's not the "expected" exception, let's not hide the error
throw ex;
// if it is the receive timeout, then reading ended
bytes = 0;
}
} while (bytes > 0);
return Encoding.GetEncoding(1252).GetString(memStream.ToArray());
}

As per your requirement, Thread.Sleep is perfectly fine to use because you are not sure when the data will be available so you might need to wait for the data to become available. I have slightly changed the logic of your function this might help you little further.
string SendCmd(string cmd, string ip, int port)
{
var client = new TcpClient(ip, port);
var data = Encoding.GetEncoding(1252).GetBytes(cmd);
var stm = client.GetStream();
stm.Write(data, 0, data.Length);
byte[] resp = new byte[2048];
var memStream = new MemoryStream();
int bytes = 0;
do
{
bytes = 0;
while (!stm.DataAvailable)
Thread.Sleep(20); // some delay
bytes = stm.Read(resp, 0, resp.Length);
memStream.Write(resp, 0, bytes);
}
while (bytes > 0);
return Encoding.GetEncoding(1252).GetString(memStream.ToArray());
}
Hope this helps!