/// <summary>
/// This method begins accepting a client from the pending connections queue. In this method, the client is
/// created and the IP address is checked for brute-force attacks. If the client is validated, then the server
/// will begin receiving data packets from the client.
/// </summary>
/// <param name="result">Represents the status of an asynchronous operation.</param>
public void AcceptConnection(IAsyncResult result)
{
try
{
// Accept the socket from the asynchronous result:
Socket clientSocket = EndAccept(result);
// If the socket is valid and the IP address was not found to be a brute-force attack on the socket's
// security algorithm, accept the connection.
if (clientSocket != null)
{
// Assign a new asynchronous state to the socket:
AsynchronousState state = new AsynchronousState(clientSocket);
OnClientConnect?.Invoke(state);
// Begin Receiving data and handling the client. If the exchange socket event is not null,
// handle the key exchange for the packet cipher; else, accept data from the client.
if (OnClientExchange != null)
{
state.Buffer = new byte[EXCHANGE_BUFFER_SIZE];
state.Socket.BeginReceive(state.Buffer, 0, EXCHANGE_BUFFER_SIZE,
SocketFlags.None, PrepareReceive, state);
}
else if (OnClientReceive != null)
{
// The server does not process key exchange. Start receiving packets immediately.
state.Buffer = new byte[sizeof(PacketHeader)];
state.Socket.BeginReceive(state.Buffer, 0, sizeof(PacketHeader),
SocketFlags.None, AnnounceReceive, state);
}
else
{
// There are no processing methods for this server!
Console.WriteLine("No processing methods defined for the " + Name);
clientSocket.Disconnect(false);
}
}
}
catch (SocketException e)
{
// Was the connection issue a problem on the server's side or the client's side?
if (e.SocketErrorCode != SocketError.Disconnecting &&
e.SocketErrorCode != SocketError.NotConnected &&
e.SocketErrorCode != SocketError.ConnectionReset &&
e.SocketErrorCode != SocketError.ConnectionAborted &&
e.SocketErrorCode != SocketError.Shutdown)
{
Console.WriteLine(e);
}
}
finally
{
BeginAccept(AcceptConnection, null);
}
}
/// <summary>
/// This method begins the client and server key exchange. The client sends key exchange data first, which is
/// picked up by the server in this socket event and processed. Then, the exchange packet is sent back to the
/// client so both the client and server have matching cipher keys, and packets are sent to the server.
/// </summary>
/// <param name="result">Represents the status of an asynchronous operation.</param>
public void PrepareReceive(IAsyncResult result)
{
// Get the asynchronous state for the connection:
AsynchronousState state = result.AsyncState as AsynchronousState;
if (state != null && state.Socket != null && state.Socket.Connected)
{
try
{
// Get the length of the incoming packet:
int length = state.Socket.EndReceive(result);
Passport passport = state.Client as Passport;
if (length > 0 && passport != null)
{
// Decrypt the exchange packet and assign variables:
passport.Packet = passport.Cipher != null
? passport.Cipher.Decrypt(state.Buffer, state.Buffer.Length)
: state.Buffer;
// Process the exchange, then start accepting data packets:
OnClientExchange(state);
state.Buffer = new byte[sizeof(PacketHeader)];
state.Socket.BeginReceive(state.Buffer, 0, sizeof(PacketHeader),
SocketFlags.None, AnnounceReceive, state);
}
else
{
state.Socket.Disconnect(false);
}
}
catch (SocketException e)
{
// Was the connection issue a problem on the client's side or the server's side?
if (e.SocketErrorCode != SocketError.Disconnecting &&
e.SocketErrorCode != SocketError.NotConnected &&
e.SocketErrorCode != SocketError.ConnectionReset &&
e.SocketErrorCode != SocketError.ConnectionAborted &&
e.SocketErrorCode != SocketError.Shutdown)
{
Console.WriteLine(e);
}
// Is the client still connected?
if (state != null && state.Socket != null && state.Socket.Connected)
{
state.Socket.Disconnect(false);
}
}
}
/// <summary>
/// This method associates the socket with an IP address and a port. It does this by creating an IP endpoint using
/// the local address and port, and requesting a remote IP endpoint using the specified IP address and port. It
/// will make an attempt to connect to the server specified.
/// </summary>
/// <param name="ip">The IP address the client will attempt to connect to.</param>
/// <param name="port">The port the socket will connect to.</param>
public bool ConnectTo(string ip, int port)
{
try
{
// Make an attempt to connect to the server:
AsynchronousState state = new AsynchronousState(this);
BeginConnect(ip, port, CompleteConnect, state);
state.Event.WaitOne();
return(Connected);
}
catch /*(SocketException exception)*/
{
/*Console.WriteLine(exception);*/
}
return(false);
}
/// <summary>
/// This method completes the connection attempt. If the attempt failed, an exception will be thrown; else,
/// the connection event will be called and the client will begin sending data to and receiving data from the
/// connected server.
/// </summary>
/// <param name="result">Represents the status of an asynchronous operation.</param>
private void CompleteConnect(IAsyncResult result)
{
try
{
// Accept the socket from the asynchronous result:
AsynchronousState state = result.AsyncState as AsynchronousState;
// If the socket is valid, complete the connection attempt.
if (state != null && state.Socket != null)
{
// Complete the connection attempt:
try
{
state.Socket.EndConnect(result);
}
catch /*(SocketException exception)*/
{
/*Console.WriteLine(exception);*/
}
finally
{
state.Event.Set();
}
// If the connection was not successful, discontinue; else, handle the on connect event:
if (!state.Socket.Connected)
{
return;
}
if (OnClientConnect != null)
{
OnClientConnect(state);
}
// Begin receiving data from the server. If the exchange socket event is not null,
// handle the key exchange for the packet cipher; else, accept data from the server.
if (OnClientExchange != null)
{
state.Buffer = new byte[EXCHANGE_BUFFER_SIZE];
state.Socket.BeginReceive(state.Buffer, 0, EXCHANGE_BUFFER_SIZE,
SocketFlags.None, PrepareReceive, state);
}
else if (OnClientReceive != null)
{
//Console.WriteLine("Starting recv process...");
// The server does not process key exchange. Start receiving packets immediately.
state.Buffer = new byte[MAX_PACKET_SIZE];
state.Socket.BeginReceive(state.Buffer, 0, MAX_PACKET_SIZE,
SocketFlags.None, AnnounceReceive, state);
}
else
{
// There are no processing methods for this server!
Console.WriteLine("No processing methods defined for the " + Name);
state.Socket.Disconnect(false);
}
}
}
catch (SocketException e)
{
// Was the connection issue a problem on the client's side or the server's side?
if (e.SocketErrorCode != SocketError.Disconnecting &&
e.SocketErrorCode != SocketError.NotConnected &&
e.SocketErrorCode != SocketError.ConnectionReset &&
e.SocketErrorCode != SocketError.ConnectionAborted &&
e.SocketErrorCode != SocketError.Shutdown)
{
Console.WriteLine(e);
}
}
}