Scan TCP 80 port and test if the destination IPs are HTTP-reachable or not.

HttpPortScan.java

import java.net.Socket;

public class HttpPortScan {

  public static void main(String[] args) {
  		final String prefix = "192.168.1.";
		for (int i = 1; i < 256; i ++) {
			final int ip = i;
			new Thread(new Runnable() {
				public void run() {
					try {
						new Socket(prefix + ip, 80);
					} catch (Exception e) {
						return;
					}
					System.out.println("connection succeeded: " + prefix + ip);
				}
			}).start();
		}
	}

}