http://www.bukkit.fr/index.php/topic/13108-pluginget-request/

ClientThread.java

package fr.neatmonster.sockets;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

public class ClientThread extends Thread {
    private final Socket socket;

    public ClientThread(final Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            final BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            System.out.println(input.readLine());
            final PrintWriter output = new PrintWriter(socket.getOutputStream());
            output.write("HTTP/1.1 200 OK\r\nContent-Language:en\r\nContent-Length:12\r\nContent-Type:text/plain; charset=utf-8\r\n\r\nHello world.");
            output.flush();
            output.close();
            input.close();
        } catch (final Exception e) {
            e.printStackTrace();
        }
    }
}

plugin.yml

name: Socket
version: 1.0
author: NeatMonster
main: fr.neatmonster.sockets.Sockets

ServerThread.java

package fr.neatmonster.sockets;

import java.io.IOException;
import java.net.ServerSocket;

public class ServerThread extends Thread {
    private ServerSocket serverSocket = null;

    @Override
    public void run() {
        try {
            serverSocket = new ServerSocket(2014);
            while (!serverSocket.isClosed())
                new ClientThread(serverSocket.accept()).start();
        } catch (final IOException e) {
            if (!e.getMessage().toLowerCase().contains("socket closed"))
                e.printStackTrace();
        }
    }

    public void stopThread() throws IOException {
        if (serverSocket != null)
            serverSocket.close();
    }
}

Sockets.java

package fr.neatmonster.sockets;

import org.bukkit.plugin.java.JavaPlugin;

public class Sockets extends JavaPlugin {
    private ServerThread serverThread;

    @Override
    public void onDisable() {
        try {
            if (serverThread != null)
                serverThread.stopThread();
        } catch (final Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onEnable() {
        serverThread = new ServerThread();
        serverThread.start();
    }
}