/// <summary>

/// SSL client is used to read/write data from/into the connected SSL server

/// </summary>

/// <remarks>Thread-safe</remarks>

public class SslClient : IDisposable

{

/// <summary>

/// Initialize SSL client with a given server IP address and port number

/// </summary>

/// <param name="context">SSL context</param>

/// <param name="address">IP address</param>

/// <param name="port">Port number</param>

public SslClient(SslContext context, IPAddress address, int port) : this(context, new IPEndPoint(address, port)) {}

/// <summary>

/// Initialize SSL client with a given server IP address and port number

/// </summary>

/// <param name="context">SSL context</param>

/// <param name="address">IP address</param>

/// <param name="port">Port number</param>

public SslClient(SslContext context, string address, int port) : this(context, new IPEndPoint(IPAddress.Parse(address), port)) {}

/// <summary>

/// Initialize SSL client with a given IP endpoint

/// </summary>

/// <param name="context">SSL context</param>

/// <param name="endpoint">IP endpoint</param>

public SslClient(SslContext context, IPEndPoint endpoint)

{

Id = Guid.NewGuid();

Context = context;

Endpoint = endpoint;

}

/// <summary>

/// SSL client Id

/// </summary>

public Guid Id { get; }

/// <summary>

/// SSL context

/// </summary>

public SslContext Context { get; private set; }

/// <summary>

/// IP endpoint

/// </summary>

public IPEndPoint Endpoint { get; private set; }

/// <summary>

/// Socket

/// </summary>

public Socket Socket { get; private set; }

/// <summary>

/// Number of bytes pending sent by the client

/// </summary>

public long BytesPending { get; private set; }

/// <summary>

/// Number of bytes sending by the client

/// </summary>

public long BytesSending { get; private set; }

/// <summary>

/// Number of bytes sent by the client

/// </summary>

public long BytesSent { get; private set; }

/// <summary>

/// Number of bytes received by the client

/// </summary>

public long BytesReceived { get; private set; }

/// <summary>

/// Option: keep alive

/// </summary>

/// <remarks>

/// This option will setup SO_KEEPALIVE if the OS support this feature

/// </remarks>

public bool OptionKeepAlive { get; set; }

/// <summary>

/// Option: no delay

/// </summary>

/// <remarks>

/// This option will enable/disable Nagle's algorithm for SSL protocol

/// </remarks>

public bool OptionNoDelay { get; set; }

/// <summary>

/// Option: receive buffer size

/// </summary>

public int OptionReceiveBufferSize

{

get => Socket.ReceiveBufferSize;

set => Socket.ReceiveBufferSize = value;

}

/// <summary>

/// Option: send buffer size

/// </summary>

public int OptionSendBufferSize

{

get => Socket.SendBufferSize;

set => Socket.SendBufferSize = value;

}

#region Connect/Disconnect client

private bool _connecting;

private SocketAsyncEventArgs _connectEventArg;

/// <summary>

/// Is the client connected?

/// </summary>

public bool IsConnected { get; private set; }

/// <summary>

/// Connect the client

/// </summary>

/// <returns>'true' if the client was successfully connected, 'false' if the client failed to connect</returns>

public virtual bool Connect()

{

if (IsConnected || _connecting)

return false;

// Setup buffers

_receiveBuffer = new Buffer();

_sendBufferMain = new Buffer();

_sendBufferFlush = new Buffer();

// Setup event args

_connectEventArg = new SocketAsyncEventArgs();

_connectEventArg.RemoteEndPoint = Endpoint;

_connectEventArg.Completed += OnAsyncCompleted;

_receiveEventArg = new SocketAsyncEventArgs();

_receiveEventArg.Completed += OnAsyncCompleted;

_sendEventArg = new SocketAsyncEventArgs();

_sendEventArg.Completed += OnAsyncCompleted;

// Create a new client socket

Socket = new Socket(Endpoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

// Async connect to the server

_connecting = true;

if (!Socket.ConnectAsync(_connectEventArg))

ProcessConnect(_connectEventArg);

return true;

}

/// <summary>

/// Disconnect the client

/// </summary>

/// <returns>'true' if the client was successfully disconnected, 'false' if the client is already disconnected</returns>

public virtual bool Disconnect()

{

if (!IsConnected && !_connecting)

return false;

// Cancel connecting operation

if (_connecting)

Socket.CancelConnectAsync(_connectEventArg);

// Reset event args

_connectEventArg.Completed -= OnAsyncCompleted;

_receiveEventArg.Completed -= OnAsyncCompleted;

_sendEventArg.Completed -= OnAsyncCompleted;

try

{

// Shutdown the socket associated with the client

Socket.Shutdown(SocketShutdown.Both);

// Close the client socket

Socket.Close();

// Dispose the client socket

Socket.Dispose();

}

catch (ObjectDisposedException) {}

// Update the connected flag

IsConnected = false;

// Update sending/receiving flags

_receiving = false;

_sending = false;

// Clear send/receive buffers

ClearBuffers();

// Call the client disconnected handler

OnDisconnected();

return true;

}

/// <summary>

/// Reconnect the client

/// </summary>

/// <returns>'true' if the client was successfully reconnected, 'false' if the client is already reconnected</returns>

public virtual bool Reconnect()

{

if (!Disconnect())

return false;

while (IsConnected)

Thread.Yield();

return Connect();

}

#endregion

#region Send/Recieve data

// Receive buffer

private bool _receiving;

private Buffer _receiveBuffer;

private SocketAsyncEventArgs _receiveEventArg;

// Send buffer

private readonly object _sendLock = new object();

private bool _sending;

private Buffer _sendBufferMain;

private Buffer _sendBufferFlush;

private SocketAsyncEventArgs _sendEventArg;

private long _sendBufferFlushOffset;

/// <summary>

/// Send data to the server

/// </summary>

/// <param name="buffer">Buffer to send</param>

/// <returns>'true' if the data was successfully sent, 'false' if the client is not connected</returns>

public virtual bool Send(byte[] buffer) { return Send(buffer, 0, buffer.Length); }

/// <summary>

/// Send data to the server

/// </summary>

/// <param name="buffer">Buffer to send</param>

/// <param name="offset">Buffer offset</param>

/// <param name="size">Buffer size</param>

/// <returns>'true' if the data was successfully sent, 'false' if the client is not connected</returns>

public virtual bool Send(byte[] buffer, long offset, long size)

{

if (!IsConnected)

return false;

if (size == 0)

return true;

lock (_sendLock)

{

// Detect multiple send handlers

bool sendRequired = _sendBufferMain.IsEmpty || _sendBufferFlush.IsEmpty;

// Fill the main send buffer

_sendBufferMain.Append(buffer, offset, size);

// Update statistic

BytesPending = _sendBufferMain.Size;

// Avoid multiple send handlers

if (!sendRequired)

return true;

}

// Try to send the main buffer

TrySend();

return true;

}

/// <summary>

/// Send text to the server

/// </summary>

/// <param name="text">Text string to send</param>

/// <returns>'true' if the text was successfully sent, 'false' if the client is not connected</returns>

public virtual bool Send(string text) { return Send(Encoding.UTF8.GetBytes(text)); }

/// <summary>

/// Try to receive new data

/// </summary>

private void TryReceive()

{

if (_receiving)

return;

if (!IsConnected)

return;

try

{

// Async receive with the receive handler

_receiving = true;

_receiveEventArg.SetBuffer(_receiveBuffer.Data, 0, (int)_receiveBuffer.Capacity);

if (!Socket.ReceiveAsync(_receiveEventArg))

ProcessReceive(_receiveEventArg);

}

catch (ObjectDisposedException) {}

}

/// <summary>

/// Try to send pending data

/// </summary>

private void TrySend()

{

if (_sending)

return;

if (!IsConnected)

return;

// Swap send buffers

if (_sendBufferFlush.IsEmpty)

{

lock (_sendLock)

{

// Swap flush and main buffers

_sendBufferFlush = Interlocked.Exchange(ref _sendBufferMain, _sendBufferFlush);

_sendBufferFlushOffset = 0;

// Update statistic

BytesPending = 0;

BytesSending += _sendBufferFlush.Size;

}

}

else

return;

// Check if the flush buffer is empty

if (_sendBufferFlush.IsEmpty)

{

// Call the empty send buffer handler

OnEmpty();

return;

}

try

{

// Async write with the write handler

_sending = true;

_sendEventArg.SetBuffer(_sendBufferFlush.Data, (int)_sendBufferFlushOffset, (int)(_sendBufferFlush.Size - _sendBufferFlushOffset));

if (!Socket.SendAsync(_sendEventArg))

ProcessSend(_sendEventArg);

}

catch (ObjectDisposedException) {}

}

/// <summary>

/// Clear send/receive buffers

/// </summary>

private void ClearBuffers()

{

lock (_sendLock)

{

// Clear send buffers

_sendBufferMain.Clear();

_sendBufferFlush.Clear();

_sendBufferFlushOffset= 0;

// Update statistic

BytesPending = 0;

BytesSending = 0;

}

}

#endregion

#region IO processing

/// <summary>

/// This method is called whenever a receive or send operation is completed on a socket

/// </summary>

private void OnAsyncCompleted(object sender, SocketAsyncEventArgs e)

{

// Determine which type of operation just completed and call the associated handler

switch (e.LastOperation)

{

case SocketAsyncOperation.Connect:

ProcessConnect(e);

break;

case SocketAsyncOperation.Receive:

ProcessReceive(e);

break;

case SocketAsyncOperation.Send:

ProcessSend(e);

break;

default:

throw new ArgumentException("The last operation completed on the socket was not a receive or send");

}

}

/// <summary>

/// This method is invoked when an asynchronous connect operation completes

/// </summary>

private void ProcessConnect(SocketAsyncEventArgs e)

{

_connecting = false;

if (e.SocketError == SocketError.Success)

{

// Apply the option: keep alive

if (OptionKeepAlive)

Socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);

// Apply the option: no delay

if (OptionNoDelay)

Socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.NoDelay, true);

// Prepare receive & send buffers

_receiveBuffer.Reserve(OptionReceiveBufferSize);

_sendBufferMain.Reserve(OptionSendBufferSize);

_sendBufferFlush.Reserve(OptionSendBufferSize);

// Reset statistic

BytesPending = 0;

BytesSending = 0;

BytesSent = 0;

BytesReceived = 0;

// Update the connected flag

IsConnected = true;

// Call the client connected handler

OnConnected();

// Call the empty send buffer handler

if (_sendBufferMain.IsEmpty)

OnEmpty();

// Try to receive something from the server

TryReceive();

}

else

{

// Call the client disconnected handler

SendError(e.SocketError);

OnDisconnected();

}

}

/// <summary>

/// This method is invoked when an asynchronous receive operation completes

/// </summary>

private void ProcessReceive(SocketAsyncEventArgs e)

{

_receiving = false;

if (!IsConnected)

return;

long size = e.BytesTransferred;

// Received some data from the client

if (size > 0)

{

// Update statistic

BytesReceived += size;

// If the receive buffer is full increase its size

if (_receiveBuffer.Capacity == size)

_receiveBuffer.Reserve(2 * size);

// Call the buffer received handler

OnReceived(_receiveBuffer.Data, size);

}

// Try to receive again if the client is valid

if (e.SocketError == SocketError.Success)

{

// If zero is returned from a read operation, the remote end has closed the connection

if (size > 0)

TryReceive();

else

Disconnect();

}

else

{

SendError(e.SocketError);

Disconnect();

}

}

/// <summary>

/// This method is invoked when an asynchronous send operation completes

/// </summary>

private void ProcessSend(SocketAsyncEventArgs e)

{

_sending = false;

if (!IsConnected)

return;

long size = e.BytesTransferred;

// Send some data to the client

if (size > 0)

{

// Update statistic

BytesSending -= size;

BytesSent += size;

// Increase the flush buffer offset

_sendBufferFlushOffset += size;

// Successfully send the whole flush buffer

if (_sendBufferFlushOffset == _sendBufferFlush.Size)

{

// Clear the flush buffer

_sendBufferFlush.Clear();

_sendBufferFlushOffset = 0;

}

// Call the buffer sent handler

OnSent(size, BytesPending + BytesSending);

}

// Try to send again if the client is valid

if (e.SocketError == SocketError.Success)

TrySend();

else

{

SendError(e.SocketError);

Disconnect();

}

}

#endregion

#region Session handlers

/// <summary>

/// Handle client connected notification

/// </summary>

protected virtual void OnConnected() {}

/// <summary>

/// Handle client handshaked notification

/// </summary>

protected virtual void OnHandshaked() {}

/// <summary>

/// Handle client disconnected notification

/// </summary>

protected virtual void OnDisconnected() {}

/// <summary>

/// Handle buffer received notification

/// </summary>

/// <param name="buffer">Received buffer</param>

/// <param name="size">Received buffer size</param>

/// <remarks>

/// Notification is called when another chunk of buffer was received from the server

/// </remarks>

protected virtual void OnReceived(byte[] buffer, long size) {}

/// <summary>

/// Handle buffer sent notification

/// </summary>

/// <param name="sent">Size of sent buffer</param>

/// <param name="pending">Size of pending buffer</param>

/// <remarks>

/// Notification is called when another chunk of buffer was sent to the server.

/// This handler could be used to send another buffer to the server for instance when the pending size is zero.

/// </remarks>

protected virtual void OnSent(long sent, long pending) {}

/// <summary>

/// Handle empty send buffer notification

/// </summary>

/// <remarks>

/// Notification is called when the send buffer is empty and ready for a new data to send.

/// This handler could be used to send another buffer to the server.

/// </remarks>

protected virtual void OnEmpty() {}

/// <summary>

/// Handle error notification

/// </summary>

/// <param name="error">Socket error code</param>

protected virtual void OnError(SocketError error) {}

#endregion

#region Error handling

/// <summary>

/// Send error notification

/// </summary>

/// <param name="error">Socket error code</param>

private void SendError(SocketError error)

{

// Skip disconnect errors

if ((error == SocketError.ConnectionAborted) ||

(error == SocketError.ConnectionRefused) ||

(error == SocketError.ConnectionReset) ||

(error == SocketError.OperationAborted))

return;

OnError(error);

}

#endregion

#region IDisposable implementation

// Disposed flag.

private bool _disposed;

// Implement IDisposable.

public void Dispose()

{

Dispose(true);

GC.SuppressFinalize(this);

}

protected virtual void Dispose(bool disposingManagedResources)

{

// The idea here is that Dispose(Boolean) knows whether it is

// being called to do explicit cleanup (the Boolean is true)

// versus being called due to a garbage collection (the Boolean

// is false). This distinction is useful because, when being

// disposed explicitly, the Dispose(Boolean) method can safely

// execute code using reference type fields that refer to other

// objects knowing for sure that these other objects have not been

// finalized or disposed of yet. When the Boolean is false,

// the Dispose(Boolean) method should not execute code that

// refer to reference type fields because those objects may

// have already been finalized."

if (!_disposed)

{

if (disposingManagedResources)

{

// Dispose managed resources here...

Disconnect();

}

// Dispose unmanaged resources here...

// Set large fields to null here...

// Mark as disposed.

_disposed = true;

}

}

// Use C# destructor syntax for finalization code.

~SslClient()

{

// Simply call Dispose(false).

Dispose(false);

}

#endregion

}