// Close socket and IO streams, change appearance/functionality of some components
private void closeAll() throws IOException {
displayArea.append("\nConnection closing");
output.close();
input.close();
connection.close();
// We are no longer connected
connection = null;
// Change components
serverField.setEditable(true);
connectButton.setLabel("Connect to server above");
enterField.setEnabled(false);
}
private void go() {
try {
// Read as long as there is input
byte[] buffer = new byte[ciphertextBlockSize];
boolean disconnectMsgSent = false;
while (connection != null && !disconnectMsgSent && input.read(buffer) != -1) {
// Decipher the bytes read in
byte[] plaintext = Ciphers.RSADecipherWSalt(buffer, decipherExp, modulus);
if (plaintext.length == 1 && plaintext[0] == 0) {
disconnectMsgSent = true;
closeAll();
} else {
// convert to a string and display
message = new String(plaintext);
displayArea.append("\n" + message);
}
}
} catch (IOException ioe) {
// Server disconnected-we can reconnect if we wish
}
}
public void actionPerformed(ActionEvent e) {
Object source = e.getSource();
// Client pressed enter in the message entry field-send it
if (source == enterField) {
// Get the message
message = e.getActionCommand();
try {
// Encipher the message
if (message.length() > plaintextBlockSize)
message = message.substring(0, plaintextBlockSize);
byte[] ciphertext =
Ciphers.RSAEncipherWSalt(message.getBytes(), BigIntegerMath.THREE, recipModulus, sr);
// Send to the server
output.write(ciphertext);
output.flush();
// Display same message in client output area
displayArea.append("\n" + message);
enterField.setText("");
} catch (IOException ioe) {
displayArea.append("\nError writing message");
}
} else if (source == connectButton) {
if (connection != null) { // Already connected-button press now means disconnect
try {
// Send final message of 0
byte[] lastMsg = new byte[1];
lastMsg[0] = 0;
output.write(Ciphers.RSAEncipherWSalt(lastMsg, BigIntegerMath.THREE, recipModulus, sr));
output.flush();
// close connection and IO streams, change some components
closeAll();
} catch (IOException ioe) {
displayArea.append("\nError closing connection");
}
} else { // Not connected-connect
// Get name of server to connect to
chatServer = serverField.getText();
displayArea.setText("Attempting connection to " + chatServer);
try {
// Set up the socket
connection = new Socket(chatServer, 55555);
displayArea.append("\nConnected to: " + connection.getInetAddress().getHostName());
// Set up the IO streams
output = new DataOutputStream(connection.getOutputStream());
output.flush();
input = new DataInputStream(connection.getInputStream());
// Exchange public keys with the server-send yours, get theirs
exchangeKeys();
// Change appearance/functionality of some components
serverField.setEditable(false);
connectButton.setLabel("Disconnect from server above");
enterField.setEnabled(true);
// Set up a thread to listen for the connection
listener =
new Thread(
new Runnable() {
public void run() {
go();
}
});
listener.start();
} catch (IOException ioe) {
displayArea.append("\nError connecting to " + chatServer);
}
}
}
}