title: How do I check if an IP is alive in java?
body: <p>There are 5 devices in my network with different IP addresses. I wish to connect to these devices and get data from them over TCP/IP socket when they are available in my network. 
  How can I check if they are available in java?</p>
  
  <pre><code>public void setUpConnection() {
      try {
          Socket client = new Socket(hostIp, hostPort);
          socketReader = client.getInputStream();
          socketWriter = new PrintWriter(client.getOutputStream());
      } catch (UnknownHostException e) {
          System.out.println("Error setting up socket connection: unknown host at " +   hostIp);
          System.out.println("host: " + hostIp + "port: " + hostPort);
      } catch (IOException e) {
          System.out.println("Error setting up socket connection: " + e);
          System.out.println("host: " + hostIp + "port:" + hostPort);
      }
  }
  </code></pre>