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POcan't ping the same IP twice
 

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    <p>I have written this code for pinging class C IP addresses on port 6789, the thread starts when I click on a button called <code>PING</code>. It will retrieve all IP addresses that has the port 6789 open. But what I need is to refresh (re-ping) every, let's say 5 seconds, and add IPs recently joined if exist and omit ones that leave the port. Unfortunately another issue appears. When I started the application the first iteration of the <code>while (true)</code> works perfectly, and it adds any IP that had the port 6789 open to the <code>ArrayList ips_List</code> and then display it on the <code>ListView</code>, and when another device joins the port, my phone will add it to the <code>ips_List</code> also. BUT in the second iteration after the Thread sleeps 5 seconds and then begins to re-ping the IPs from (x.x.x.1 - x.x.x.254) to see if another IP had joined the port when pinging to an IP previously pinged, the Socket will throw IOException (as written in the code).</p> <p>Why is that happening?</p> <pre><code>Thread pingo = new Thread(new Runnable() { public void run() { while (true) { if (readableNetmask.equals("255.255.255.0")) { for (int i = 2; i &lt;= 25; i++) { String ip_address = readableIPAddress; String oct1 = "", oct2 = "", oct3 = "", oct4 = ""; StringTokenizer stok = new StringTokenizer( ip_address, "."); while (stok.hasMoreTokens()) { oct1 = stok.nextToken(); oct2 = stok.nextToken(); oct3 = stok.nextToken(); oct4 = stok.nextToken(); } to_ping_ip = oct1 + "." + oct2 + "." + oct3 + "." + String.valueOf(i); if (pingAddress(to_ping_ip, 6789)) { ips_List.add(to_ping_ip); } } } // delay 10 seconds, then re-ping try { Thread.sleep(5000); } catch (InterruptedException e) { break; } handler.post(new UpdateIPListViewRunnable()); } } }); pingo.start(); </code></pre> <p>PingAddress() function:</p> <pre><code>public boolean pingAddress(String ip, int port) { Socket socket = new Socket(); try { socket.connect(new InetSocketAddress(ip, port), 200); socket.close(); } catch (IOException e) { return false; } return true; } </code></pre> <p>List where addresses appear:</p> <pre><code>static public class UpdateIPListViewRunnable implements Runnable { public void run() { arrayAdapter.clear(); for (int i = 0; i &lt; ips_List.size(); i++) { arrayAdapter.add(ips_List.get(i)); arrayAdapter.notifyDataSetChanged(); } ips_List.clear(); } } </code></pre>
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    1. COPlease ask a complete, self-contained question.
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      1. USDave Newton
    2. COit's from the previous question [Ping every 5 seconds]; When pinging a specific IP it suscceeds but when the thread enters the seconds loop after the Sleeping 5 seconds ... the ping failed when pinging an IP that has previously pinged and has the port 6789 opened.. I don't know why ???
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      1. USspac3hit
    3. COPlease ask a complete, self-contained question? That means the question must stand on its own. Include your code, a problem statement, etc.
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      1. USDave Newton
 

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