/// <summary>
/// Function to send data to the client.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ButtonSendMessage_Click(object sender, EventArgs e)
{
const string NULLDATAERRORMESSAGE = "Field cannot be left empty";
//If there is no message to send, display an error message in the ErrorProvider
ClassLibrary.CheckTextBoxNotNull(TextBoxTypeMessage, ErrorProvider);
if (ErrorProvider.GetError(TextBoxTypeMessage) == NULLDATAERRORMESSAGE)
{
return;
}
//Encrypt the message and transmit it
string encryptedMessage = ClassLibrary.SymmetricEncryptDecrypt(TextBoxTypeMessage.Text, symmetricKey);
byte[] bt = Encoding.UTF8.GetBytes(encryptedMessage);
try
{
connectedClient.Client.Send(bt);
}
catch (Exception ex)
{
MyMessageBox.ShowMessage(ex.ToString());
return;
}
//Display the text in the list box
ListBoxChat.Items.Add(staffMember.StaffFirstName + ": " + TextBoxTypeMessage.Text + Environment.NewLine);
TextBoxTypeMessage.Clear();
}
private void ButtonSendMessage_Click(object sender, EventArgs e)
{
const string NULLDATAERRORMESSAGE = "Field cannot be left empty";
ClassLibrary.CheckTextBoxNotNull(TextBoxTypeMessage, ErrorProvider);
//As long as the user has some sort of input in the textbox, the message will send
if (ErrorProvider.GetError(TextBoxTypeMessage) == NULLDATAERRORMESSAGE)
{
return;
}
//Encrypt the message
string encryptedMessage = ClassLibrary.SymmetricEncryptDecrypt(TextBoxTypeMessage.Text, symmetricKey);
//Encode the message and send it
serverStream.Write(Encoding.UTF8.GetBytes(encryptedMessage), 0, Encoding.UTF8.GetByteCount(encryptedMessage));
serverStream.Flush();
//Display the message to the rich text box
sbSend.Clear();
sbSend.Append(student.StudentFirstName);
sbSend.Append(": ");
sbSend.Append(TextBoxTypeMessage.Text);
sbSend.Append(Environment.NewLine);
RichTextBoxChatWindow.SelectionColor = Color.Blue;
RichTextBoxChatWindow.AppendText(sbSend.ToString());
TextBoxTypeMessage.Clear();
}
private void SendStudentID()
{
string sID = ClassLibrary.SymmetricEncryptDecrypt(student.StudentID, symmetricKey);
serverStream.Write(Encoding.UTF8.GetBytes(sID), 0, Encoding.UTF8.GetByteCount(sID));
serverStream.Flush();
}
//Staff name must be sent before the client and server begin chatting,
//so the users know who they're communicating with
private void SendStaffName()
{
string encryptedMessage = ClassLibrary.SymmetricEncryptDecrypt(staffMember.StaffFirstName, symmetricKey);
byte[] bt = Encoding.UTF8.GetBytes(encryptedMessage);
try
{
connectedClient.Client.Send(bt);
}
catch (Exception ex)
{
MyMessageBox.ShowMessage("Failed to send staff first name: " + ex.ToString());
}
}
/// <summary>
/// Callback function called when data is received on the socket
/// </summary>
/// <param name="ar"></param>
public void OnReceive(IAsyncResult ar)
{
string content = string.Empty;
int bytesRead;
// Retrieve the state object and the handler socket
//from the asynchronous state object.
StateObject state = (StateObject)ar.AsyncState;
Socket clientSocket = state.workSocket;
if (clientSocket.Connected)
{
// Read data from the client socket.
try
{
bytesRead = clientSocket.EndReceive(ar);
if (bytesRead > 0)
{
if (!symmetricKeyReceived)
{
byte[] temp = state.buffer;
int i = temp.Length - 1;
while (temp[i] == 0)
{
--i;
}
// now data[i] is the last non-zero byte
byte[] receivedData = new byte[i + 1];
Array.Copy(temp, receivedData, i + 1);
//Get the symmetric key after decrypting it using RSA
byte[] decryptedKey = rsa.Decrypt(receivedData, false);
string decryptedKeyString = Convert.ToBase64String(decryptedKey);
symmetricKey = decryptedKeyString;
symmetricKeyReceived = true;
SendStaffName();
clientSocket.BeginReceive(state.buffer, 0, StateObject.BufferSize,
0, new AsyncCallback(OnReceive), state);
return;
}
// There might be more data, so store the data received so far.
state.sb.Remove(0, state.sb.Length);
state.sb.Append(Encoding.UTF8.GetString(state.buffer, 0, bytesRead));
if (!studentNameReceived)
{
string encryptedStudentID = state.sb.ToString();
string sID = ClassLibrary.SymmetricEncryptDecrypt(encryptedStudentID, symmetricKey);
try
{
SqlConnector db = new SqlConnector();
List <StudentModel> listStudents = db.GetStudent_ByStudentID(sID);
connectedStudent = listStudents[0];
}
catch
{
MyMessageBox.ShowMessage("Access to the database failed.");
return;
}
SetTextBoxStudentName();
studentNameReceived = true;
clientSocket.BeginReceive(state.buffer, 0, StateObject.BufferSize,
0, new AsyncCallback(OnReceive), state);
return;
}
// Display text in rich text box
string received = state.sb.ToString();
content = ClassLibrary.SymmetricEncryptDecrypt(received, symmetricKey);
SetText(content);
clientSocket.BeginReceive(state.buffer, 0, StateObject.BufferSize,
0, new AsyncCallback(OnReceive), state);
}
else
{
//Disconnect request has 0 bytes.
//So if 0 byte message detected: disable further communication.
SetSendButton(false);
SetTextBoxConnectionStatus(Color.Red);
clientStream.Dispose();
clientStream.Close();
connectedClient.Client.Dispose();
connectedClient.Client.Close();
}
}
catch (SocketException socketException)
{
//WSAECONNRESET, the other side closed impolitely
if (socketException.ErrorCode == 10054 || ((socketException.ErrorCode != 10004) && (socketException.ErrorCode != 10053)))
{
// Complete the disconnect request.
string remoteIP =
((IPEndPoint)clientSocket.RemoteEndPoint).Address.ToString();
string remotePort =
((IPEndPoint)clientSocket.RemoteEndPoint).Port.ToString();
this.ownerForm.DisconnectClient(remoteIP, remotePort);
clientSocket.Close();
clientSocket = null;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message.ToString());
}
}
}
/// <summary>
/// A callback function triggered when data is received on the socket.
/// </summary>
/// <param name="ar"></param>
public void OnReceive(IAsyncResult ar)
{
string content = string.Empty;
//Retrieve the state object and the handler socket from the asynchronous state object
state = (StateObject)ar.AsyncState;
Socket handler = state.workSocket;
int bytesRead;
if (handler.Connected)
{
//Read data from the client socket
try
{
bytesRead = handler.EndReceive(ar);
if (bytesRead > 0)
{
//There might be more data, so store the data received so far
state.sb.Remove(0, state.sb.Length);
//Translate the bytes into a readable format
state.sb.Append(Encoding.UTF8.GetString(state.buffer, 0, bytesRead));
string s = state.sb.ToString();
//Before the server and client can begin chatting, the server must send its
//public key over, the client then sends a generated symmetric key back, encrypted
//using the public key. Then the server must send the staff member's name while
//the client must send the student ID.
if (!publicKeyReceived)
{
rsa = new RSACryptoServiceProvider(2048);
//Save the public key received to rsa
rsa.FromXmlString(state.sb.ToString());
SendSymmetricKey();
publicKeyReceived = true;
//Continue to asynchronously receive data from the server
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(OnReceive), state);
return;
}
if (!nameReceived)
{
SendStudentID();
string encryptedStaffName = state.sb.ToString();
staffName = ClassLibrary.SymmetricEncryptDecrypt(encryptedStaffName, symmetricKey);
nameReceived = true;
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(OnReceive), state);
return;
}
//Display text in TextBox
string received = state.sb.ToString();
content = ClassLibrary.SymmetricEncryptDecrypt(received, symmetricKey);
//Function used to display text in the rich text box. A delegate function
//must be used as we're not on the main thread.
SetText(content);
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(OnReceive), state);
}
else
{
//If no data is received, then an error has occured as null messages cannot be sent.
MyMessageBox.ShowMessage("Error occured: no data was supplied.");
}
}
catch (SocketException socketEx)
{
//WSAECONNRESET: if the other side closes impolitely
//(they shut down the server or crash for some reason)
//Cut the connection and reset everything
if (socketEx.ErrorCode == 10054 || ((socketEx.ErrorCode != 10004) && (socketEx.ErrorCode != 10053)))
{
handler.Close();
SetTextBoxConnectionStatusBackgroundColour(Color.Red);
SetSendButton(false);
SetConnectButton(true);
SetDisconnectButton(false);
serverStream.Close();
server.Close();
nameReceived = false;
publicKeyReceived = false;
}
}
catch (Exception ex)
{
//Anyother unexpected error is displayed here
MyMessageBox.ShowMessage(ex.Message);
}
}
else
{
handler.Close();
}
}