1 files changed, 65 insertions, 1 deletions

diff --git a/app/src/main/java/mygram/droid/Discovery.java b/app/src/main/java/mygram/droid/Discovery.java
index 1d3e0be..56777f3 100644
--- a/app/src/main/java/mygram/droid/Discovery.java
+++ b/app/src/main/java/mygram/droid/Discovery.java
@@ -12,14 +12,33 @@
  * for more details.
  */
 
-
 package mygram.droid;
 
+import android.content.Context;
+import android.net.ConnectivityManager;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+
 import org.json.JSONException;
 import org.json.JSONObject;
 
+import java.io.IOException;
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.net.URI;
+import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
 /** Finds Foldergram instances on the LAN. */
+// ponytail: probes only the TV's /24 on the default port; manual URL entry covers proxies and other ports.
 final class Discovery {
+	static final int PORT = 4141;
+
 	private Discovery() {
 	}
 
@@ -32,4 +51,49 @@ final class Discovery {
 			return false;
 		}
 	}
+
+	/** The TV's own IPv4 address, or null when offline. */
+	static String localIpv4(Context c) {
+		ConnectivityManager cm = c.getSystemService(ConnectivityManager.class);
+		LinkProperties lp = cm.getLinkProperties(cm.getActiveNetwork());
+		if (lp != null)
+			for (LinkAddress a : lp.getLinkAddresses())
+				if (a.getAddress() instanceof Inet4Address)
+					return a.getAddress().getHostAddress();
+		return null;
+	}
+
+	/** Base URLs of instances answering on the /24 around self. Blocks a few seconds. */
+	static List<String> scan(String self) throws InterruptedException {
+		String prefix = self.substring(0, self.lastIndexOf('.') + 1);
+		ExecutorService pool = Executors.newFixedThreadPool(64);
+		List<String> found = Collections.synchronizedList(new ArrayList<>());
+		for (int i = 1; i < 255; i++) {
+			String base = "http://" + prefix + i + ":" + PORT;
+			pool.execute(() -> {
+				try {
+					if (isFoldergram(Api.request(base, "GET", "/health", null, 800)))
+						found.add(base);
+				} catch (IOException e) {
+					// nothing listening there
+				}
+			});
+		}
+		pool.shutdown();
+		pool.awaitTermination(20, TimeUnit.SECONDS);
+		List<String> out = new ArrayList<>(found);
+		Collections.sort(out);
+		return out;
+	}
+
+	/** Reverse-DNS name plus IP when there is a name, else the IP. */
+	static String label(String base) {
+		String ip = URI.create(base).getHost();
+		try {
+			String name = InetAddress.getByName(ip).getCanonicalHostName();
+			return name.equals(ip) ? ip : name + "  " + ip;
+		} catch (UnknownHostException e) {
+			return ip;
+		}
+	}
 }