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);
}
Related
I wrote this method using UDP socket with ReceiveTimeout = 1000. And sometimes it loses second packet:
private static byte[] ReceivePlainData(Socket socket) {
var recievedData = new List<byte>();
var buffer = new byte[1024];
do {
int recievedAmount;
while (true) {
try {
recievedAmount = socket.Receive(buffer);
}
catch (SocketException) {
continue;
}
break;
}
recievedData.AddRange(buffer.Take(recievedAmount));
} while (socket.Available > 0);
return recievedData.ToArray();
}
Socket initialization:
using (var socket = new Socket(SocketType.Dgram, ProtocolType.Udp) {
ReceiveTimeout = 1000
})
What do i need to change to make this method work correctly?
Socket.Available only tells you if data has been received and available for immediate reading. It doesn't tell you if the stream is complete or not. The sender may still be in the process of generating or transmitting more data. If you intend to consume the entire response and are relying on the socket to be closed by the sender when there is no more data, continue reading from the socket until the number of bytes returned is 0 (indicating the socket was closed normally) or an exception occurs (indicating abnormal termination).
MemoryStream stream = new MemoryStream();
int received;
var buffer = new byte[8096];
do {
received = socket.Receive(buffer);
stream.Write(buffer, 0, received);
} while (received > 0);
// Use the stream
// byte[] bytes = stream.ToArray();
Set your socket's ReceiveTimeout to the maximum amount of time you're willing to wait between bytes before aborting.
i have an issue where im not receiving any bytes from the connected TcpClient!
Server: (i attempt to add the received message into a listbox, but nothing comes out.
//tl is a TcpListener
//I set this up in a 500 milisecond loop. No worries about that.
if (tl.Pending())
{
TcpClient tcp = tl.AcceptTcpClient();
var s = tcp.GetStream();
int bytesRead = s.Read(new byte[tcp.ReceiveBufferSize], 0,
tcp.ReceiveBufferSize);
string dataReceived = Encoding.ASCII.GetString(new
byte[tcp.ReceiveBufferSize], 0, bytesRead);
listBox1.Items.Add(dataReceived);
tcp.Close();
oac++; //Overall connection count
label3.Text = "Overall Connections: " + oac; //logging connections
}
Client:
void Send(){
TcpClient c = new TcpClient(Im not including my ip., 4444);
System.IO.StreamWriter w = new System.IO.StreamWriter(c.GetStream());
byte[] bytesToSend = ASCIIEncoding.ASCII.GetBytes($"Username: \"
{textBox1.Text}\" | Password: \"{textBox2.Text}\"");
NetworkStream nwStream = c.GetStream();
nwStream.Write(bytesToSend, 0, bytesToSend.Length);
nwStream.Flush();
}
I The connection works, but theres some issues receiving data. it just comes out blank
On serverside, your problem is that you renew toy byte array new byte[tcp.ReceiveBufferSize]. You could also do something like this:
using( var inputStream = new MemoryStream() )
{
tcp.GetStream().CopyTo(inputStream);
Encoding.ASCII.GetString(inputStream.ToArray());
listBox1.Items.Add(dataReceived);
...
}
Remember using on all IDisposable's, else you will run out of resources.
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.
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.
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.