public class Server {
    
    private static final int MAX = 10;
    
    public Server() {
        try {
            ServerSocket ss = new ServerSocket(8888);
            System.out.println("服务器启动……");
            
            while (true) {
                if (ClientSocket.getCount() < MAX) {
                    Socket s = ss.accept();
                    new ClientSocket(s);
                } else {
                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
            
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        new Server();
    }

}

class ClientSocket extends Thread {
    private static int count = 0;
    private Socket s = null;
    private InetAddress ia = null;
    private String ip = null;
    
    public ClientSocket(Socket s) {
        count++;
        this.s = s;
        this.ia = s.getInetAddress();
        this.ip = this.ia.getHostAddress();
        this.start();
    }
    
    public void run() {
        try {
            File f = new File("pop.jpg");
            if (f.exists()) {
                OutputStream os = s.getOutputStream();
                BufferedOutputStream bos = new BufferedOutputStream(os);
                
                FileInputStream fis = new FileInputStream(f);
                BufferedInputStream bis = new BufferedInputStream(fis);
                byte[] data = new byte[1024];
                int len = 0;
                
                System.out.println("开始向" + ip + "传送文件");
                
                bos.write(("FILE:" + f.getName()).getBytes());
                bos.flush();
                
                while ((len = bis.read(data)) != -1) {
                    bos.write(data, 0, len);
                    bos.flush();
                }
                
//                bos.write("quit".getBytes());
                bis.close();
                bos.close();
                System.out.println("向" + ip + "传送文件完毕");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        count--;
        try {
            s.close();
            System.out.println("关闭");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static int getCount() {
        return count;
    }
}

------解决方案--------------------

楼主我以前写过这样的例子，是C/S架构的，你要的话E-mail我一下，我发给你参考参考279074838@qq.com