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Sending message from server and receive from the client end

Here is a sample server program written in c# which receives an id from a client. My sample code is given below. I want to send a string array to client and display is on the client console.
The sample array string can be:
string[] arr1 = new string[] { "one", "two", "three" };
What additional code I need to add with the following server and client code?
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
namespace server
{
class Program
{
static void Main(string[] args)
{
TcpListener tcpListener = new TcpListener(IPAddress.Any, 1234);
tcpListener.Start();
while (true)
{
TcpClient tcpClient = tcpListener.AcceptTcpClient();
byte[] data = new byte[1024];
NetworkStream ns = tcpClient.GetStream();
int recv = ns.Read(data, 0, data.Length);
string id = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine(id);
}
}
}
}

Since Tcp is a stream based protocol, I would suggest you use something higher level that plain byte[]. If all you need is to send strings from client to server and vice-versa, I think a StreamReader and a StreamWriter on both ends would work great. On the StreamWriter side, you've got a WriteLine(string) method to send to the client and the StreamReader has a similar method ReadLine().
Here's a simplification that you could apply to your model:
Server side:
TcpClient client; //Let's say it's already initialized and connected properly
StreamReader reader = new StreamReader(client.GetStream());
while(client.Connected)
{
string message = reader.ReadLine(); //If the string is null, the connection has been lost.
}
Client side:
TcpClient client; //Same, it's initialized and connected
StreamWriter writer = new StreamWriter(client.GetStream());
writer.AutoFlush = true; //Either this, or you Flush manually every time you send something.
writer.WriteLine("My Message"); //Every message you want to send
StreamWriter will end every message with a new line so that the StreamReader knows when the full string has been received.
Note that a TCP connection is a full-duplex connection. Meaning you can simultaneously send and receive data. Checkout the WriteLineAsync(string) and ReadLineAsync() methods if you want to implement something like this.
If you want to send arrays, establish a simple protocol looking a bit like this:
Send the length of the string[]. Example: writer.WriteLine(myArray.Length.ToString);
Receive and parse this length
Send all strings one after the other on the server side
Receive all strings in a for loop on the client side.
Once you received all strings, repeat the process.

Sending String Array to client
TcpListener tcpListener = new TcpListener(IPAddress.Any, 1234);
tcpListener.Start();
while (true)
{
TcpClient tcpClient = tcpListener.AcceptTcpClient();
byte[] data = new byte[1024];
NetworkStream ns = tcpClient.GetStream();
string[] arr1 = new string[] { "one", "two", "three" };
var serializer = new XmlSerializer(typeof(string[]));
serializer.Serialize(tcpClient.GetStream(), arr1);
tcpClient.GetStream().Close()
tcpClient.Close();
int recv = ns.Read(data, 0, data.Length);
in this line
string id = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine(id);
}
}
Client
try
{
byte[] data = new byte[1024];
string stringData;
TcpClient tcpClient = new TcpClient("127.0.0.1", 1234);
NetworkStream ns = tcpClient.GetStream();
var serializer = new XmlSerializer(typeof(string[]));
var stringArr = (string[])serializer.Deserialize(tcpClient.GetStream());
foreach (string s in stringArr)
{
Console.WriteLine(s);
}
string input = Console.ReadLine();
ns.Write(Encoding.ASCII.GetBytes(input), 0, input.Length);
ns.Flush();
}
catch (Exception e)
{
Console.Write(e.Message);
}
Console.Read();

C# one tcp networkstream accepted

I have an issue with a TCP Listener.
The scenario is the following:
- I am receiving TCP packets (8192 Bytes each) and I would like to dump the data received from NetworkStream into a file (using FileStream);
- What I saw is that all the TCP packets arrived to the TCP listener but only the first 8192 Bytes are dumped into the file.
I believe that the NetStream is faster than the IO operation to the file.
My code is:
try
{
// Set TcpListener on port 8
Int32 portN = 8;
TcpListener server = new TcpListener(IPAddress.Any, portN);
// Start listening for client requests
server.Start();
Console.Write("Waiting for connection... ");
// Define File Name
string RcvFileName = #"c:\ethernet\out_file.raw";
// Buffer for reading data
int NrBytesRec;
Byte[] RecData = new Byte[8192];
// enter into listening loop
while (true)
{
// Perform a blocking call to accept requests.
// You can also user server.AcceptSocket() here.
TcpClient client = server.AcceptTcpClient();
Console.WriteLine("Connected!");
// Get a stream object for reading and writing
NetworkStream netstream = client.GetStream();
// Append data into file
FileStream fs_wr = new FileStream(RcvFileName, FileMode.Append, FileAccess.Write);
// Dump data
while ((NrBytesRec = netstream.Read(RecData, 0, RecData.Length)) > 0)
{
fs_wr.Write(RecData, 0, NrBytesRec);
Console.WriteLine("Received: {0}", NrBytesRec);
}
netstream.Close();
fs_wr.Close();
//client.Close();
}

C# client/server Question

I'm incredibly confused as to what is going on here. I've been putting in break points and I just can't seem to understand. Basically, I have a client and a server. I want the client to send two separate strings of data. From putting in break points, I noticed that my client does in fact fill both strings with the appropriate data. However, the server never ever sees the second string. Why is this happening and how do I fix it? Any help at all would be greatly appreciate! Below is my code:
Server:
private static void HandleClientComm(object client)
{
/** creating a list which contains DatabaseFile objects **/
List<DatabaseFile> theDatabase = new List<DatabaseFile>();
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
StringBuilder response = new StringBuilder();
byte[] message = new byte[4096];
int bytesRead;
do
{
bytesRead = 0;
try
{
/*do
{
bytesRead = clientStream.Read(message, 0, message.Length);
response.Append(Encoding.ASCII.GetString(message, 0, bytesRead));
} while (clientStream.DataAvailable);*/
when i change this commented code to bytesRead = clientStream.Read(message, 0, 4096); i get an IOException Error that reads as follows: Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host. Hence, i changed it to a do while loop. How do i get around this IOException and accept the second string?
ASCIIEncoding encoder = new ASCIIEncoding();
String file = encoder.GetString(message, 0, bytesRead);
Menu.Insert(theDatabase, file);
}
catch (Exception)
{
// A socket error has occured
break;
}
if (bytesRead == 0)
{
// The client has disconnected from the server
break;
}
} while (clientStream.DataAvailable);
// Release connections
clientStream.Close();
tcpClient.Close();
}
Client:
static void Main(string[] args)
{
TcpClient client = new TcpClient();
IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 8888);
client.Connect(serverEndPoint);
NetworkStream clientStream = client.GetStream();
NetworkStream clientStream2 = client.GetStream();
ASCIIEncoding encoder = new ASCIIEncoding();
ASCIIEncoding encoder2 = new ASCIIEncoding();
String text = System.IO.File.ReadAllText("FirstNames.txt");
String text2 = System.IO.File.ReadAllText("LastNames.txt");
byte[] buffer = encoder.GetBytes(text);
Console.ReadLine();
clientStream.Write(buffer, 0, buffer.Length);
clientStream.Flush();
Console.ReadLine();
byte[] buffer2 = encoder2.GetBytes(text2);
clientStream2.Write(buffer2, 0, buffer2.Length);
clientStream2.Flush();
Console.ReadLine();
}
}

The communication between client and server happens like this (note that the order of steps is just for illustration purposes, the actual order at runtime may be different):
Client: client.Connect(serverEndPoint)
Server: HandleClientComm(newClient)
Client: clientStream.Write(buffer, 0, buffer.Length)
Server: bytesRead = clientStream.Read(message, 0, message.Length)
Note that Read is not guaranteed to read entire message. It is perfectly ok to return just the portion that has been received so far
Client: Console.ReadLine()
Server: while (clientStream.DataAvailable)
There is no data on the stream - the client has not sent any. This would likely happen even without ReadLine - there is a window of time before the client sends data again
Server: tcpClient.Close()
Client: clientStream2.Write(buffer2, 0, buffer2.Length)
You can get an exception here, or not - depending on whether the server has already closed the connection, in any case the server is not reading anymore.
You need to define your own message protocol that both server and client will honor. For example, you can have the client close the connection when it is done sending:
Client:
using (var client = new TcpClient("localhost", 8888))
using (var clientStream = client.GetStream())
{
var buffer = Encoding.ASCII.GetBytes( File.ReadAllText("FirstNames.txt") );
clientStream.Write(buffer, 0, buffer.Length);
buffer = Encoding.ASCII.GetBytes( File.ReadAllText("LastNames.txt") );
clientStream.Write(buffer, 0, buffer.Length);
}
Server:
using (var tcpClient = (TcpClient)client)
using (var clientStream = tcpClient.GetStream())
{
// Store everything that the client sends.
// This will work if the client closes the connection gracefully
// after sending everything
var receivedData = new MemoryStream();
clientStream.CopyTo(receivedData);
var rawBytes = receivedData.ToArray();
var file = Encoding.ASCII.GetString(rawBytes, 0, rawBytes.Length);
Menu.Insert(theDatabase, file);
}
The protocol is simple, and may be enough for your case. However, there are issues with it which should be addressed in production code (e.g. what if the client sends too much data, exhausting server memory, what if the client stops sending without closing the connection, etc.)

because while (clientStream.DataAvailable) is no longer true after your first client call.

You are exiting your client-recv loop in your server just because DatAvailable is false. This means if the client were to send a frame of data (which you consume) and pause then your server would see no data available at that moment and disconnect, even if a split second later another frame of data from the client was about to come in. Almost always, the end of a dialog is based on the content of the data being passed. You can certainly never try to rely on the fact that DataAvailable happens to be false one time.
As a follow-up, if you provide more info on the protocol that is used we can give more assitance. For example, if the prototcol is that two strings are sent with CR/LF at the end then the server loop should be inspecting the buffer for that to know when to disconnect.

How To Signal End Of Data Without Closing NetworkStream in C#

I have a client application that serializes a object and sends it to a server application. The server should deserialize the object, make changes to it, then serialize it and send it back.
Server Code:
TcpClient client = server.AcceptTcpClient();
using(NetworkStream stream = client.GetStream())
{
using(StreamReader streamReader = new StreamReader(stream))
{
string xmlData = streamReader.ReadToEnd();
}
}
The ReadToEnd doesn't return unless the client closes the stream. But if the client closes the stream, I can't send a response.
Is there a better way to do this?

You can signal "end of data" by closing only your half of the duplex TCP connection. This is accomplished with Socket.Disconnect.
See how it works with this example, which I kept similar to yours. The client sends the data and then calls Disconnect; this allows ReadToEnd to return while still keeping the server's half of the connection open. The server then sends a response and also disconnects, after which both parties can Close their end of the connection to tear it down.
static void Main(string[] args)
{
Action clientCode = () =>
{
var buffer = new byte[100];
var clientSocket = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
clientSocket.Connect(IPAddress.Loopback, 6690);
clientSocket.Send(buffer);
clientSocket.Disconnect(false);
Console.WriteLine("Client: message sent and socket disconnected.");
while (true) {
var bytesRead = clientSocket.Receive(buffer);
if (bytesRead == 0) {
break;
}
Console.WriteLine("Client: read " + bytesRead + " bytes.");
}
clientSocket.Dispose();
};
var server = new TcpListener(IPAddress.Loopback, 6690);
var thread = new Thread(new ThreadStart(clientCode));
server.Start();
thread.Start();
var client = server.AcceptTcpClient();
using(NetworkStream stream = client.GetStream()) {
using(StreamReader streamReader = new StreamReader(stream))
{
var data = streamReader.ReadToEnd();
Console.WriteLine("Server: read " + data.Length + " bytes.");
// Since we 're here we know that the client has disconnected.
// Send the response before StreamReader is disposed, because
// that will cause the socket itself to be closed as well!
Thread.Sleep(TimeSpan.FromSeconds(1));
Console.WriteLine("Server: sending response.");
stream.Write(new byte[10], 0, 10);
Console.WriteLine("Server: closing socket.");
}
}
server.Stop();
Console.WriteLine("Server: waiting for client thread to complete.");
thread.Join();
return;
}

You could use a higher level framework like WCF, or if you are hell-bent on managing your own streams, then don't use ReadToEnd()- use ReadLine() (and have the client send messages as lines), or use Read() and have a special character (a sentinel) represent the end of a message.

TCP Client Server Problem

I have the following code for the server application:
TcpListener recSock = new TcpListener(400);
recSock.Start();
TcpClient client = recSock.AcceptTcpClient();
NetworkStream netStream = client.GetStream();
Byte[] data = new Byte[256];
int i;
while((i = netStream.Read(data, 0, data.Length)) != 0) {
string cmd = ASCIIEncoding.ASCII.GetString(data, 0, i);
Console.WriteLine(cmd);
if(cmd == "R") {
RestartScheduler();
}
}
client.Close();
And the client looks like:
TcpClient client = new TcpClient();
client.Connect("VM-SCHEDULER", 400);
NetworkStream netStream = client.GetStream();
Byte[] data = ASCIIEncoding.ASCII.GetBytes("R");
netStream.Write(data, 0, data.Length);
netStream.Flush();
client.Close();
All is fine the first time the client connects the "R" command is read and the RestartScheduler() method is called, however all subsequent commands fail until the server is restarted.
I have used telnet to connect to the server after the first attempt and it is still listening on the port.
Where am i going wrong?
EDIT:
Basically what I am trying to accomplish is that the server will listen always, a client will then connect send the "R" command then close the connection. The client must be able to connect to the server at any time to issue the command. There will only be 1 client at any given time.

If there is no data to be read, netStream.Read will return 0 and your while loop will exit, disconnecting the client at client.Close();. You have nothing in your code to allow the server to continue receiving in this scenario.
You need to keep listening for connections until the application is shutdown, so put the listen and GetStream in a while loop. Since Stream.Read is a blocking call, you should have some data for the data reading while loop (unless timeout occurs). Otherwise it will close the connection and go back to listening for a new one.
Note: I've not included any error handling in here, you'll need to add that yourself.
TcpListener recSock = new TcpListener(400);
recSock.Start();
while (!stopping)
{
TcpClient client = recSock.AcceptTcpClient();
NetworkStream netStream = client.GetStream();
Byte[] data = new Byte[256];
int i = netStream.Read(data, 0, data.Length);
while(i != 0)
{
string cmd = ASCIIEncoding.ASCII.GetString(data, 0, i);
Console.WriteLine(cmd);
if(cmd == "R") {
RestartScheduler();
}
i = stream.Read(bytes, 0, bytes.Length);
}
client.Close();
Thread.Sleep(1); // Will allow the stopping bool to be updated
}
Module level add:
private bool stopping = false;
In your shutdown function:
stopping = true;

Are you connecting multiple times, or sending multiple commands down the same connection? If you could provide a short but complete program to demonstrate the problem, that would really help.
My guess is that you're running into problems due to reading multiple commands from a single connection in one go, but it's hard to know without more information. Don't forget that a single call to Write from the client can easily result in multiple reads at the server end - or vice versa.

Well the server will exit after the first command it receives, no?

At the least, you're missing using statements:
TcpListener recSock = new TcpListener(IPAddress.Loopback, 400);
recSock.Start();
using (TcpClient client = recSock.AcceptTcpClient())
{
using (NetworkStream netStream = client.GetStream())
{
Byte[] data = new Byte[256];
int i;
while ((i = netStream.Read(data, 0, data.Length)) != 0)
{
string cmd = Encoding.ASCII.GetString(data, 0, i);
Console.WriteLine(cmd);
if (cmd == "R")
{
RestartScheduler();
}
}
}
client.Close();
}
and
using (TcpClient client = new TcpClient())
{
client.Connect("VM-SCHEDULER", 400);
using (NetworkStream netStream = client.GetStream())
{
Byte[] data = Encoding.ASCII.GetBytes("R");
netStream.Write(data, 0, data.Length);
netStream.Flush();
}
client.Close();
}