IRC Hacks [Electronic resources] نسخه متنی

Hack 34 A Simple Java IRC Client

If you want to make an IRC client that can run
on a variety of platforms, Java provides one possible
solution.

To illustrate how easy it
is to connect to IRC with other languages, you can apply the protocol
information learned from the earlier Telnet experiments [Hack #31] and port the Perl example to
Java. Using a Java program to connect to IRC is perhaps the most
flexible solution, as it can run on any machine that has a
Java Virtual Machine installed and can
also run inside a web browser as an Applet.

5.5.1 The Code

Save
the
following code to a file called HackBot.java:

import java.io.*;
import java.net.*;
public class HackBot {
public static void main(String[] args) throws Exception {
// The server to connect to and our details.
String server = "irc.freenode.net";
String nick = "simple_bot";
String login = "simple_bot";
// The channel which the bot will join.
String channel = "#irchacks";
// Connect directly to the IRC server.
Socket socket = new Socket(server, 6667);
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream( )));
BufferedReader reader = new BufferedReader(
new InputStreamReader(socket.getInputStream( )));
// Log on to the server.
writer.write("NICK " + nick + "\r\n");
writer.write("USER " + login + " 8 * : Java IRC Hacks Bot\r\n");
writer.flush( );
// Read lines from the server until it tells us we have connected.
String line = null;
while ((line = reader.readLine( )) != null) {
if (line.indexOf("004") >= 0) {
// We are now logged in.
break;
}
else if (line.indexOf("433") >= 0) {
System.out.println("Nickname is already in use.");
return;
}
}
// Join the channel.
writer.write("JOIN " + channel + "\r\n");
writer.flush( );
// Keep reading lines from the server.
while ((line = reader.readLine( )) != null) {
if (line.toLowerCase( ).startsWith("PING ")) {
// We must respond to PINGs to avoid being disconnected.
writer.write("PONG " + line.substring(5) + "\r\n");
writer.write("PRIVMSG " + channel + " :I got pinged!\r\n");
writer.flush( );
}
else {
// Print the raw line received by the bot.
System.out.println(line);
}
}
}
}

5.5.2 Running the Hack

You must first compile the hack with the
javac command. If you have the Java SDK installed
and set up correctly, you can do this from the command prompt:

% javac HackBot.java

This will compile the source code into platform-independent bytecode
and create the file HackBot.class. You can now
run the HackBot from the same command prompt:

% java HackBot

The HackBot will now leap into life.

5.5.3 Results

When you
run the Java HackBot, it should connect to the IRC server you
specified. Any exceptions will be allowed to propagate from
the main method, so if something goes wrong, you will find out what
it was. When it comes to adding a few more features to this IRC bot,
you may like to consider dealing with these exceptions more neatly.
As with the simple Perl bot, the HackBot should display the raw lines
it receives from the server after it has connected successfully.

Each time this bot receives a PING from the
server, it will respond with a PONG and use the
PRIVMSG command to tell the channel that it got
pinged. The format of this message will be something like this:

PRIVMSG #irchacks :I got pinged!

The PRIVMSG command is to send messages to
individual users as well as channels. All you have to do is write
your nickname instead of the channel name:

PRIVMSG YourNick :I got pinged!

This hack forms the basis of a bot that is able to connect to an IRC
server and stay connected. With a little experimentation with the IRC
protocol [Hack #78], you can add
extra features to this bot and make it do something useful.