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ChargenServer.java
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102 lines (93 loc) · 3.34 KB
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import java.nio.*;
import java.nio.channels.*;
import java.net.*;
import java.util.*;
import java.io.IOException;
public class ChargenServer {
public static int DEFAULT_PORT = 19;
public static void main(String[] args) {
int port;
try {
port = Integer.parseInt(args[0]);
} catch (RuntimeException ex) {
port = DEFAULT_PORT;
}
System.out.println("Listening for connections on port " + port);
byte[] rotation = new byte[95*2];
for (byte i = ' '; i <= '~'; i++) {
rotation[i -' '] = i;
rotation[i + 95 - ' '] = i;
}
ServerSocketChannel serverChannel;
Selector selector;
try {
serverChannel = ServerSocketChannel.open();
ServerSocket ss = serverChannel.socket();
InetSocketAddress address = new InetSocketAddress(port);
ss.bind(address);
serverChannel.configureBlocking(false);
selector = Selector.open();
serverChannel.register(selector, SelectionKey.OP_ACCEPT);
} catch (IOException ex) {
ex.printStackTrace();
return;
}
while (true) {
try {
selector.select();
} catch (IOException ex) {
ex.printStackTrace();
break;
}
Set<SelectionKey> readyKeys = selector.selectedKeys();
Iterator<SelectionKey> iterator = readyKeys.iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
iterator.remove();
try {
if (key.isAcceptable()) {
ServerSocketChannel server = (ServerSocketChannel) key.channel();
SocketChannel client = server.accept();
System.out.println("Accepted connection from " + client);
client.configureBlocking(false);
SelectionKey key2 = client.register(selector, SelectionKey.
OP_WRITE);
ByteBuffer buffer = ByteBuffer.allocate(74);
buffer.put(rotation, 0, 72);
buffer.put((byte) '\r');
buffer.put((byte) '\n');
buffer.flip();
key2.attach(buffer);
} else if (key.isWritable()) {
SocketChannel client = (SocketChannel) key.channel();
ByteBuffer buffer = (ByteBuffer) key.attachment();
if (!buffer.hasRemaining()) {
// Refill the buffer with the next line
buffer.rewind();
// Get the old first character
int first = buffer.get();
// Get ready to change the data in the buffer
buffer.rewind();
// Find the new first characters position in rotation
int position = first - ' ' + 1;
// copy the data from rotation into the buffer
buffer.put(rotation, position, 72);
// Store a line break at the end of the buffer
buffer.put((byte) '\r');
buffer.put((byte) '\n');
// Prepare the buffer for writing
buffer.flip();
}
client.write(buffer);
}
} catch (IOException ex) {
key.cancel();
try {
key.channel().close();
}
catch (IOException cex) {}
}
}
}
}
}