Develop Reference

Fix for Ssl Asynchronous Client in C#

I'm attempting to write a .Net Framework 4.7.2 client that can communicate with a proto buffer payload eventually, over SSL. I think the best approach would be a TAP model, but I've had less luck finding a working example to repeatedly do the send (if data to send) and process server messages as and when the server replies, and therefore I've gone with the APM approach here below.
My problem is I get a "The BeginWrite method cannot be called when another write is pending" error in SendWorker(). My server does receive the connection and the message. I can work on the SSL cert later.
My output is:
Client connected.
Client is selecting a local certificate.
To quit, press the enter key.
Client is selecting a local certificate.
Validating the server certificate.
Certificate error: RemoteCertificateNameMismatch
Writing data to the server.
Writing data to the server.
The test code is:
using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Net.Security;
using System.Net.Sockets;
using System.Security.Authentication;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading;
namespace SslClient
{
// This is a client side of a
// client-server application that communicates using the
// SslStream and TcpClient classes.
// After connecting to the server and authenticating,
// the client should repeatedly send items from a q and listen for any replies
public class SslTcpClient
{
// complete is used to terminate the application when all
// asynchronous calls have completed or any call has thrown an exception.
// complete might be used by any of the callback methods.
private bool complete = false;
// e stores any exception thrown by an asynchronous method so that
// the mail application thread can display the exception and terminate gracefully.
// e might be used by any of the callback methods.
private Exception e = null;
// readData and buffer holds the data read from the server.
// They is used by the ReadCallback method.
private StringBuilder readData = new StringBuilder();
private byte[] buffer = new byte[2048];
EventWaitHandle _trigger = new AutoResetEvent(false);
private TcpClient _tcpClient;
private SslStream _sslStream;
private Thread _senderThread;
private readonly object _locker = new object();
public ConcurrentQueue<byte[]> WriteQueue = new ConcurrentQueue<byte[]>();
// The following method is invoked by the CertificateValidationDelegate.
public bool ValidateServerCertificate(
object sender,
X509Certificate certificate,
X509Chain chain,
SslPolicyErrors sslPolicyErrors)
{
Console.WriteLine("Validating the server certificate.");
if (sslPolicyErrors == SslPolicyErrors.None)
return true;
Console.WriteLine("Certificate error: {0}", sslPolicyErrors);
// Do not allow this client to communicate with unauthenticated servers.
return true; // ToDo
}
public X509Certificate SelectLocalCertificate(
object sender,
string targetHost,
X509CertificateCollection localCertificates,
X509Certificate remoteCertificate,
string[] acceptableIssuers)
{
Console.WriteLine("Client is selecting a local certificate.");
if (acceptableIssuers != null &&
acceptableIssuers.Length > 0 &&
localCertificates != null &&
localCertificates.Count > 0)
{
// Use the first certificate that is from an acceptable issuer.
foreach (X509Certificate certificate in localCertificates)
{
string issuer = certificate.Issuer;
if (Array.IndexOf(acceptableIssuers, issuer) != -1)
return certificate;
}
}
if (localCertificates != null &&
localCertificates.Count > 0)
return localCertificates[0];
return null;
}
private void AuthenticateCallback(IAsyncResult ar)
{
SslStream stream = (SslStream)ar.AsyncState;
try
{
stream.EndAuthenticateAsClient(ar);
}
catch (Exception authenticationException)
{
e = authenticationException;
//complete = true;
return;
}
}
public void ProduceConsumerQueue(TcpClient tcpClient, SslStream sslStream)
{
_tcpClient = tcpClient;
_sslStream = sslStream;
_senderThread = new Thread(SenderWorker);
_senderThread.Start();
}
public void Send(byte[] payload)
{
WriteQueue.Enqueue(payload);
_trigger.Set();
}
//our workhorse. This will just sit and wait until there is something to send
//it will continue to send until there is nothing left
void SenderWorker()
{
while (!complete)
{
string msg = null;
if (WriteQueue.Count > 0)
{
byte[] message;
WriteQueue.TryDequeue(out message);
if (_tcpClient.Connected && message.Length > 0)
{
if (_sslStream.CanWrite)
{
_sslStream.BeginWrite(message, 0, message.Length,
new AsyncCallback(WriteCallback),
_sslStream);
}
}
}
else
{
_trigger.WaitOne(); // Zero msgs left.. just wait
}
}
}
private void WriteCallback(IAsyncResult ar)
{
SslStream stream = (SslStream)ar.AsyncState;
try
{
Console.WriteLine("Writing data to the server.");
stream.EndWrite(ar);
// Asynchronously read a message from the server.
//stream.BeginRead(buffer, 0, buffer.Length,
// new AsyncCallback(ReadCallback),
// stream);
}
catch (Exception writeException)
{
e = writeException;
complete = true;
return;
}
}
private void ReadCallback(IAsyncResult ar)
{
// Read the message sent by the server.
// The end of the message is signaled using the
// "<EOF>" marker.
SslStream stream = (SslStream)ar.AsyncState;
int byteCount = -1;
try
{
Console.WriteLine("Reading data from the server.");
byteCount = stream.EndRead(ar);
// Use Decoder class to convert from bytes to UTF8
// in case a character spans two buffers.
Decoder decoder = Encoding.UTF8.GetDecoder();
char[] chars = new char[decoder.GetCharCount(buffer, 0, byteCount)];
decoder.GetChars(buffer, 0, byteCount, chars, 0);
readData.Append(chars);
// Check for EOF or an empty message.
if (byteCount != 0)
{
// We are not finished reading.
// Asynchronously read more message data from the server.
stream.BeginRead(buffer, 0, buffer.Length,
new AsyncCallback(ReadCallback),
stream);
}
else
{
Console.WriteLine("Message from the server: {0}", readData.ToString());
}
if (WriteQueue.Count>0)
{
//byte[] message;
//WriteQueue.TryDequeue(out message);
//if (message.Length > 0)
//{
// stream.BeginWrite(message, 0, message.Length,
// new AsyncCallback(WriteCallback),
// ar);
//}
}
}
catch (Exception readException)
{
e = readException;
complete = true;
return;
}
complete = true;
}
public int Main(string serverName, int port)
{
// Create a TCP/IP client socket.
TcpClient client = new TcpClient(serverName, port);
Console.WriteLine("Client connected.");
// Create an SSL stream that will close the client's stream.
SslStream sslStream = new SslStream(
client.GetStream(),
false,
new RemoteCertificateValidationCallback(ValidateServerCertificate),
new LocalCertificateSelectionCallback(SelectLocalCertificate)
);
var clientCertificate = FindClientCertificate(X509FindType.FindBySubjectName, "IIS Express Development Certificate"); // IIS Express Development Certificate
var clientCertificates = new X509CertificateCollection(new X509Certificate[] { clientCertificate });
// Begin authentication.
// The server name must match the name on the server certificate.
sslStream.BeginAuthenticateAsClient(
"UIClient",
clientCertificates,
SslProtocols.Tls12,
false,/* cert revocation */
new AsyncCallback(AuthenticateCallback),
sslStream);
// sslStream.AuthenticateAsClient("UIClient", clientCertificates, SslProtocols.Tls12, false);
ProduceConsumerQueue(client, sslStream);
// User can press a key to exit application, or let the
// asynchronous calls continue until they complete.
Console.WriteLine("To quit, press the enter key.");
do
{
// Real world applications would do work here
// while waiting for the asynchronous calls to complete.
Send(System.Text.Encoding.UTF8.GetBytes("hello".ToArray()));
System.Threading.Thread.Sleep(100);
} while (complete != true && Console.KeyAvailable == false);
if (Console.KeyAvailable)
{
Console.ReadLine();
Console.WriteLine("Quitting.");
client.Close();
sslStream.Close();
return 1;
}
if (e != null)
{
Console.WriteLine("An exception was thrown: {0}", e.ToString());
}
sslStream.Close();
client.Close();
Console.WriteLine("Good bye.");
return 0;
}
private static X509Certificate FindClientCertificate(X509FindType type, string item)
{
return Find(type, item, StoreLocation.CurrentUser) ?? Find(type, item, StoreLocation.LocalMachine);
}
private static X509Certificate Find(X509FindType t, string item, StoreLocation location)
{
using (var store = new X509Store(location))
{
store.Open(OpenFlags.OpenExistingOnly);
var certs = store.Certificates.Find(t, item, true);
if (t == X509FindType.FindBySubjectName)
{
return store.Certificates.OfType<X509Certificate2>().FirstOrDefault(x => x.FriendlyName == item);
}
return certs.OfType<X509Certificate>().FirstOrDefault();
}
}
}
}
How can it be fixed? Is there a better complete solution that you can share?
Thanks in advance,
Steve

The way of building a simple http proxy

I'm trying to build a simple http proxy, which does four really basic things:
Accepts connection from web-browser (using TcpClient/TcpListener).
Reads request from its stream.
Reads hostname and initiates connection with host.
Loads content from webpage and forwards it back to the client.
The troubles i met with:
Sometimes page wouldn't load at all.
Sometimes browser gives me an error 'The content has wrong encryption'(in firefox).
Seldom i can see content corruption(plain text instead of HTML).
What i've done:
HttpListener class that contains methods for listening for incoming requests and invoking event OnNewRequestReceived:
public void Listen()
{
Listener.Start();
while (true)
{
var client = Listener.AcceptTcpClient();
Task.Run(() => StartReceivingData(client));
}
}
public void StartReceivingData(TcpClient client)
{
NetworkStream clientStream = client.GetStream();
var buffer = new byte[16000];
while (true)
{
try
{
if (!clientStream.CanRead)
return;
//connection is closed
if (clientStream.Read(buffer).Equals(0))
return;
OnNewRequestReceived?.Invoke(this, new RequestReceivedEventArgs() { User = client, Request = buffer });
} // when clientStream is disposed, exception is thrown.
catch { return; }
}
}
HttpClient class which basically contains a method that subscribes to event described above:
private void Listener_OnNewConnectionReceived(object sender, RequestReceivedEventArgs e)
{
string hostname = HttpQueryParser.GetHostName(e.Request);
NetworkStream proxyClientStream = e.User.GetStream();
try
{
if (firewall.CheckIfBlocked(hostname))
{
//send error page
e.User.GetStream().Write(Encoding.ASCII.GetBytes("<html><body style=\"padding:0; margin:0;\"><img style=\"padding:0; margin:0; width:100%; height:100%;\" src=\"https://www.hostinger.co.id/tutorial/wp-content/uploads/sites/11/2017/08/what-is-403-forbidden-error-and-how-to-fix-it.jpg\"</body></html>"));
return;
}
var targetServer = new TcpClient(hostname, 80);
NetworkStream targetServerStream = targetServer.GetStream();
targetServerStream.Write(e.Request);
var responseBuffer = new byte[32];
for (int offsetCounter = 0; true; ++offsetCounter)
{
var bytesRead = targetServerStream.Read(responseBuffer, 0, responseBuffer.Length);
// Console.WriteLine($"Read {bytesRead} from {hostname}.");
if (bytesRead.Equals(0))
return;
proxyClientStream.Write(responseBuffer, 0, responseBuffer.Length);
if (offsetCounter.Equals(0))
{
var headers = Encoding.UTF8.GetString(responseBuffer).Split("\r\n");
logger.Log(new HttpRequestEntry()
{
ResponseCode = headers[0].Substring(headers[0].IndexOf(" ") + 1),
Hostname = hostname
});
}
}
}
catch { return; }
finally { proxyClientStream.Dispose(); }
}
So, i'm guessing there's a problem with my buffer size, but changing it to higher values actually doesn't change anything .

Ok so i don't know what's the problem with my byte arrays was, but i made it work, using Stream.CopyTo , which i was quite surprized about - it works on two NetworkStreams.
Here's working method if you are curious:
private void Listener_OnNewConnectionReceived(object sender, RequestReceivedEventArgs e)
{
string hostname = HttpQueryParser.GetHostName(e.Request);
NetworkStream proxyClientStream = e.User.GetStream();
try
{
if (firewall.CheckIfBlocked(hostname))
{
//send error page
e.User.GetStream().Write(Encoding.ASCII.GetBytes("<html><body style=\"padding:0; margin:0;\"><img style=\"padding:0; margin:0; width:100%; height:100%;\" src=\"https://www.hostinger.co.id/tutorial/wp-content/uploads/sites/11/2017/08/what-is-403-forbidden-error-and-how-to-fix-it.jpg\"</body></html>"));
return;
}
var targetServer = new TcpClient(hostname, 80);
NetworkStream targetServerStream = targetServer.GetStream();
targetServerStream.Write(e.Request);
var responseBuffer = new byte[32];
//this is to capture status of http request and log it.
targetServerStream.Read(responseBuffer, 0, responseBuffer.Length);
proxyClientStream.Write(responseBuffer, 0, responseBuffer.Length);
var headers = Encoding.UTF8.GetString(responseBuffer).Split("\r\n");
logger.Log(new HttpRequestEntry()
{
ResponseCode = headers[0].Substring(headers[0].IndexOf(" ") + 1),
Hostname = hostname
});
targetServerStream.CopyTo(proxyClientStream);
}
catch { return; }
finally { proxyClientStream.Dispose(); }
}

Wait for response from the Serial Port and then send next data

I am reading data in bytes from .bin file and split the whole byte data into 16-16 bytes frames, so I want to 16 bytes frame one by one and wait until the first frame finished its cycle.
Callback method of SerialPort class:
private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
// Read data from serial port:
byte[] buffer = new byte[serialPort.BytesToRead];
serialPort.Read(buffer, 0, buffer.Length);
StringBuilder sb = new StringBuilder();
List<string> response = new List<string>();
for (int i = 0; i < buffer.Length; i++)
{
string currentByte = string.Format("{0:X2}", buffer[i]);
response.Add(currentByte);
sb.AppendFormat("{0:X2}", buffer[i]);
}
string responesCode = response[1].ToString();
if (responesCode == "44")
{
// Wait until the first response is not received
foreach (var packet in packetList.Skip(1))
{
// This method which sending the the data
this.ReadByteDataFromFile(packet);
}
}
}
FdBrowseFile_Click button click:
private void FdBrowseFile_Click(object sender, RoutedEventArgs e)
{
Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
Nullable<bool> result = dlg.ShowDialog();
if (result == true)
{
byte[] fileBytes = File.ReadAllBytes(filename);
foreach (byte[] copySlice in fileBytes.Slices(16))
{
var splitedByteArray = copySlice;
if (splitedByteArray.Length != 16)
{
byte[] padd = new byte[16];
var startAt = 0;
Array.Copy(splitedByteArray, 0, padd, startAt, splitedByteArray.Length);
packetList.Add(padd);
}
else
{
packetList.Add(splitedByteArray);
}
}
ReadByteDataFromFile(packetList[0]);
}
}
ReadByteDataFromFile method:
public void ReadByteDataFromFile(byte[] packet) {
try {
byte[] mBuffer = new byte[24];
byte[] payload = new byte[16];
int i = 0;
foreach(var bytes in packet) {
payload[i++] = bytes;
}
CheckSumHelper checkSumHelper = new CheckSumHelper();
var ckSum = checkSumHelper.GetCheckSum(payload);
mBuffer[0] = 0x02;
mBuffer[1] = 0x10;
mBuffer[2] = CheckSumHelper.GetBytesFromDecimal(packet[0]);
mBuffer[3] = CheckSumHelper.GetBytesFromDecimal(packet[1]);
mBuffer[4] = CheckSumHelper.GetBytesFromDecimal(packet[2]);
mBuffer[5] = CheckSumHelper.GetBytesFromDecimal(packet[3]);
mBuffer[6] = CheckSumHelper.GetBytesFromDecimal(packet[4]);
mBuffer[7] = CheckSumHelper.GetBytesFromDecimal(packet[5]);
mBuffer[8] = CheckSumHelper.GetBytesFromDecimal(packet[6]);
mBuffer[9] = CheckSumHelper.GetBytesFromDecimal(packet[7]);
mBuffer[10] = CheckSumHelper.GetBytesFromDecimal(packet[8]);
mBuffer[11] = CheckSumHelper.GetBytesFromDecimal(packet[9]);
mBuffer[12] = CheckSumHelper.GetBytesFromDecimal(packet[10]);
mBuffer[13] = CheckSumHelper.GetBytesFromDecimal(packet[11]);
mBuffer[14] = CheckSumHelper.GetBytesFromDecimal(packet[12]);
mBuffer[15] = CheckSumHelper.GetBytesFromDecimal(packet[13]);
mBuffer[16] = CheckSumHelper.GetBytesFromDecimal(packet[14]);
mBuffer[17] = CheckSumHelper.GetBytesFromDecimal(packet[15]);
mBuffer[18] = 0x17;
mBuffer[19] = 0x00;
mBuffer[20] = 0x00;
mBuffer[21] = 0x00;
mBuffer[22] = Convert.ToByte(int.Parse(ckSum, System.Globalization.NumberStyles.HexNumber));
mBuffer[23] = 0x03;
serialPort.Write(mBuffer, 0, mBuffer.Length);
} catch (Exception ex) {
ExceptionHandler exceptionHandler = new ExceptionHandler();
exceptionHandler.HandleException(ex);
}
}
How I can add a delay for ReadByteDataFromFile method?

What you need is a way to block the execution of some code, until something else has happened, or - how to get things running on two threads synchronously.
.NET has quite a few classes in the System.Threading namespace for synchronization. We'll use AutoResetEvent here.
Think of AutoResetEvent as a turnstile.
You can't move forward if the the person on the other side stops.
When you move forward, you call Wait - and it blocks you from moving,
until someone calls Set on it.
Now if we apply that to our problem:
We need to stop sending data until we get an acceptable response.
So call Wait when sending data, and let the response handling code call Set to let it move forward.
Here's an example which simulates a modem.
You send some AT commands, it responds, but the responses always end with \r\n.
var port = new SerialPort("COM2");
port.Open();
var mre = new AutoResetEvent(false);
var buffer = new StringBuilder();
port.DataReceived += (s, e) =>
{
buffer.Append(port.ReadExisting());
if (buffer.ToString().IndexOf("\r\n") >= 0)
{
Console.WriteLine("Got response: {0}", buffer);
mre.Set(); //allow loop to continue
buffer.Clear();
}
};
var commandsToSend = new string[] { "AT", "AT", "AT+CSQ" };
var responseTimeout = TimeSpan.FromSeconds(10);
foreach (var command in commandsToSend)
{
try
{
Console.WriteLine("Write '{0}' to {1}", command, port.PortName);
port.WriteLine(command);
Console.WriteLine("Waiting for response...");
//this is where we block
if (!mre.WaitOne(responseTimeout))
{
Console.WriteLine("Did not receive response");
//do something
}
}
catch (TimeoutException)
{
Console.WriteLine("Write took longer than expected");
}
catch
{
Console.WriteLine("Failed to write to port");
}
}
Console.ReadLine();
Sample output when tested through virtual serial port:
(I just reply with OK<CR><LF>)
Write 'AT' to COM2
Waiting for response...
Got response: OK
Write 'AT' to COM2
Waiting for response...
Got response: OK
Write 'AT+CSQ' to COM2
Waiting for response...
Did not receive response

Wait in a loop for a full response after you write a first frame.
// Set read timeout to value recommended in the communication protocol specification
// so serial port operations don't stuck.
_port.WriteTimeout = 200;
_port.ReadTimeout = 200;
public void OnClick()
{
// Write first frame.
_port.Write(...);
// Now wait for the full response.
// Expected response length. Look for the constant value from the device communication
// protocol specification or extract from the response header (first response bytes) if
// there is any specified in the protocol.
int count = ...;
var buffer = new byte[count];
var offset = 0;
while (count > 0)
{
var readCount = _port.Read(buffer, offset, count);
offset += readCount;
count -= readCount;
}
// Now buffer contains full response or TimeoutException instance is thrown by SerialPort.
// Check response status code and write other frames.
}
In order to not block UI thread you most probably still need to utilize synchronous API and Task.Run(). See C# await event and timeout in serial port communication discussion on StackOverflow.
For more information check Top 5 SerialPort Tips article by Kim Hamilton.

Exceptions: System.NullReferenceException [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
NullReferenceException on instanciated object?
What is a NullReferenceException in .NET?
I have built a TCP client in C#, when the client cannot connect Im getting the below.
I keep getting a NullReference Exception with the following code, I cannot figure how to catch it or stop it.. any help will be greatly appreciated.
Its happening at "int a = sReponseData.Length"
{
string sMesg = "LogOn Ext:" + txtdevice.Text;
SendMessage(sMesg);
int a = sResponseData.Length;
//Geting the Script out of the message.
if (a > 10)
{
string stemp = sResponseData;
string[] sSplit = stemp.Split(new Char[] { ';'});
foreach (string s in sSplit)
{
if ((s.Trim() != "Tag") & (s.Trim() != "StopStart"))
sScript = s;
}
}
}
}
and here is the sMesg
{
InitializeComponent();
try
{
// Create a TcpClient.
// Note, for this client to work you need to have a TcpServer
// connected to the same address as specified by the server, port
// combination.
//Int32 port = 13000;
TcpClient client = new TcpClient("127.0.0.1", 32111);
// Translate the passed message into ASCII and store it as a Byte array.
Byte[] data = System.Text.Encoding.ASCII.GetBytes(sMsg);
// Get a client stream for reading and writing.
// Stream stream = client.GetStream();
NetworkStream stream = client.GetStream();
// Send the message to the connected TcpServer.
stream.Write(data, 0, data.Length);
//MessageBox.Show("Sent: {0}" + sMsg);
// Receive the TcpServer.response.
// String to store the response ASCII representation.
sResponseData = String.Empty;
if (stream.CanRead)
{
byte[] myReadBuffer = new byte[1024];
StringBuilder myCompleteMessage = new StringBuilder();
int numberOfBytesRead = 0;
// Incoming message may be larger than the buffer size.
do
{
numberOfBytesRead = stream.Read(myReadBuffer, 0, myReadBuffer.Length);
myCompleteMessage.AppendFormat("{0}", Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead));
}
while (stream.DataAvailable);
// Print out the received message to the console.
sResponseData = myCompleteMessage.ToString();
//MessageBox.Show(sResponseData);
}
else
{
sResponseData = ("3");
MessageBox.Show("TagIt Server is unavalible at this moment.");
}
// Close everything.
stream.Close();
client.Close();
}
catch (ArgumentNullException e)
{
WriteLog("ArgumentNullException: {0}" + e);
MessageBox.Show("TagIt Server is unavalible at this moment.");
}
catch (SocketException e)
{
WriteLog("SocketException: {0}" + e);
MessageBox.Show("TagIt Server is unavalible at this moment.");
}
}

You can check if Response data has value or not:
Something like:
int a;
try
{
if(sResponseData==null || sResponseData=="" )
{
MessageBox.Show("ResponseData is NULL or Empty"); //Shows Error
}
else
{
//SresponseData has value
string sMesg = "LogOn Ext:" + txtdevice.Text;
SendMessage(sMesg);
a= Convert.ToInt32(sResponseData).Length;
//Geting the Script out of the message.
if (a > 10)
{
string stemp = sResponseData;
string[] sSplit = stemp.Split(new Char[] { ';'});
foreach (string s in sSplit)
{
if ((s.Trim() != "Tag") & (s.Trim() != "StopStart"))
sScript = s;
}
}
}
}
catch (Execption ex)
{
MessageBox.Show(ex.Message); //Shows Error
}

Before checking length of sResponseData make sure you check whether sResponseData is null or not.

iPhone Push Notification issue with c#

I cannot send the notification to iphone. Everything seems fine, as the service works out fine, but to message to iphone.
Here is the code:
using (NetworkStream networkStream = client.GetStream())
{
Console.WriteLine("Client connected.");
//X509Certificate clientCertificate = new X509Certificate(#"C:\Users\yagizozturk\Documents\Visual Studio 2010\Projects\GarantiKampanya\Garanti.Web.Service\apns-prod.pem", "");
X509Certificate clientCertificate = new X509Certificate(#"C:\Users\yagizozturk\Documents\Visual Studio 2010\Projects\GarantiKampanya\Garanti.Web.Service\apns-prod-cert.p12", "1234567");
X509CertificateCollection clientCertificateCollection = new X509CertificateCollection(new X509Certificate[1] { clientCertificate });
// Create an SSL stream that will close the client's stream.
SslStream sslStream = new SslStream(
client.GetStream(),
false,
new RemoteCertificateValidationCallback(ValidateServerCertificate),
null
);
try
{
sslStream.AuthenticateAsClient("gateway.sandbox.push.apple.com", clientCertificateCollection, SslProtocols.Default, false);
}
catch (AuthenticationException e)
{
Console.WriteLine("Exception: {0}", e.Message);
if (e.InnerException != null)
{
Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
}
Console.WriteLine("Authentication failed - closing the connection.");
client.Close();
return;
}
}
}
string token = "f5aaa8a729613480c79270085e881c435535dac4704dc00b082bfa8fc84aca10";
//string token = "f5aaa8a7 29613480 c7927008 5e881c43 5535dac4 704dc00b 082bfa8f c84aca90";
System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
byte[] myByteArray = new byte[10000000];
myByteArray = encoding.GetBytes(token);
//int i = 0;
//foreach(char c in token.ToCharArray())
//{
// myByteArray [i] = (byte)c;
// i++;
//}
GeneratePayload(myByteArray, "test", "default");
}
private static byte[] GeneratePayload(byte[] deviceToken, string message, string sound)
{
MemoryStream memoryStream = new MemoryStream();
// Command
memoryStream.WriteByte(0);
byte[] tokenLength = BitConverter.GetBytes((Int16)32);
Array.Reverse(tokenLength);
// device token length
memoryStream.Write(tokenLength, 0, 2);
// Token
memoryStream.Write(deviceToken, 0, 32);
// String length
string apnMessage = string.Format("{{\"aps\":{{\"alert\":{{\"body\":\"{0}\",\"action-loc-key\":null}},\"sound\":\"{1}\"}}}}",
message,
sound);
byte[] apnMessageLength = BitConverter.GetBytes((Int16)apnMessage.Length);
Array.Reverse(apnMessageLength);
// message length
memoryStream.Write(apnMessageLength, 0, 2);
// Write the message
memoryStream.Write(System.Text.ASCIIEncoding.ASCII.GetBytes(apnMessage), 0, apnMessage.Length);
return memoryStream.ToArray();
}
// The following method is invoked by the RemoteCertificateValidationDelegate.
public static bool ValidateServerCertificate(
object sender,
X509Certificate certificate,
X509Chain chain,
SslPolicyErrors sslPolicyErrors)
{
if (sslPolicyErrors == SslPolicyErrors.None)
return true;
Console.WriteLine("Certificate error: {0}", sslPolicyErrors);
// Do not allow this client to communicate with unauthenticated servers.
return false;
}

I got the answer. Here is a complete code to send push notifications from c#.
public bool ConnectToAPNS()
{
X509Certificate2Collection certs = new X509Certificate2Collection();
// Add the Apple cert to our collection
certs.Add(getServerCert());
// Apple development server address
string apsHost;
if (getServerCert().ToString().Contains("Production"))
apsHost = "gateway.push.apple.com";
else
apsHost = "gateway.sandbox.push.apple.com";
// Create a TCP socket connection to the Apple server on port 2195
TcpClient tcpClient = new TcpClient(apsHost, 2195);
// Create a new SSL stream over the connection
sslStream = new SslStream(tcpClient.GetStream());
// Authenticate using the Apple cert
sslStream.AuthenticateAsClient(apsHost, certs, SslProtocols.Default, false);
//PushMessage();
return true;
}
private X509Certificate getServerCert()
{
X509Certificate test = new X509Certificate();
//Open the cert store on local machine
X509Store store = new X509Store(StoreLocation.CurrentUser);
if (store != null)
{
// store exists, so open it and search through the certs for the Apple Cert
store.Open(OpenFlags.ReadOnly);
X509Certificate2Collection certs = store.Certificates;
if (certs.Count > 0)
{
int i;
for (i = 0; i < certs.Count; i++)
{
X509Certificate2 cert = certs[i];
if (cert.FriendlyName.Contains("Apple Production Push Services: KFDLV3XL6Y:ZJPGDMQBKC"))
{
//Cert found, so return it.
return certs[i];
}
}
}
return test;
}
return test;
}
private static byte[] HexToData(string hexString)
{
if (hexString == null)
return null;
if (hexString.Length % 2 == 1)
hexString = '0' + hexString; // Up to you whether to pad the first or last byte
byte[] data = new byte[hexString.Length / 2];
for (int i = 0; i < data.Length; i++)
data[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
return data;
}
public bool PushMessage(string token, string message)
{
String cToken = token;
String cAlert = message;
int iBadge = 1;
// Ready to create the push notification
byte[] buf = new byte[256];
MemoryStream ms = new MemoryStream();
BinaryWriter bw = new BinaryWriter(ms);
bw.Write(new byte[] { 0, 0, 32 });
byte[] deviceToken = HexToData(cToken);
bw.Write(deviceToken);
bw.Write((byte)0);
// Create the APNS payload - new.caf is an audio file saved in the application bundle on the device
string msg = "{\"aps\":{\"alert\":\"" + cAlert + "\",\"badge\":" + iBadge.ToString() + ",\"sound\":\"new.caf\"}}";
// Write the data out to the stream
bw.Write((byte)msg.Length);
bw.Write(msg.ToCharArray());
bw.Flush();
if (sslStream != null)
{
sslStream.Write(ms.ToArray());
return true;
}
return false;
}