Add port conflict exception (#4565)

Signed-off-by: Gabriel Fukushima <gabrielfukushima@gmail.com>

util/src/main/java/org/hyperledger/besu/util/NetworkUtility.java

@@ -14,20 +14,27 @@
  */
 package org.hyperledger.besu.util;
 
+import java.io.IOException;
+import java.net.DatagramSocket;
 import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.NetworkInterface;
+import java.net.ServerSocket;
 import java.net.SocketException;
 import java.net.UnknownHostException;
 import java.util.function.Supplier;
 
 import com.google.common.base.Suppliers;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class NetworkUtility {
   public static final String INADDR_ANY = "0.0.0.0";
   public static final String INADDR6_ANY = "0:0:0:0:0:0:0:0";
 
+  private static final Logger LOG = LoggerFactory.getLogger(NetworkUtility.class);
+
   private NetworkUtility() {}
 
   private static final Supplier<Boolean> ipv6Available =
@@ -98,4 +105,30 @@ public class NetworkUtility {
               "%s port requires a value between 1 and 65535. Got %d.", portTypeName, port));
     }
   }
+
+  public static boolean isPortAvailableForTcp(final int port) {
+    try (final ServerSocket serverSocket = new ServerSocket()) {
+      serverSocket.setReuseAddress(true);
+      serverSocket.bind(new InetSocketAddress(port));
+      return true;
+    } catch (IOException ex) {
+      LOG.trace(String.format("Failed to open port %d for TCP", port), ex);
+    }
+    return false;
+  }
+
+  private static boolean isPortAvailableForUdp(final int port) {
+    try (final DatagramSocket datagramSocket = new DatagramSocket(null)) {
+      datagramSocket.setReuseAddress(true);
+      datagramSocket.bind(new InetSocketAddress(port));
+      return true;
+    } catch (IOException ex) {
+      LOG.trace(String.format("failed to open port %d for UDP", port), ex);
+    }
+    return false;
+  }
+
+  public static boolean isPortAvailable(final int port) {
+    return isPortAvailableForTcp(port) && isPortAvailableForUdp(port);
+  }
 }

util/src/test/java/org/hyperledger/besu/util/NetworkUtilityTest.java

@@ -16,7 +16,9 @@ package org.hyperledger.besu.util;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.io.IOException;
 import java.net.InetSocketAddress;
+import java.net.ServerSocket;
 
 import org.junit.Test;
 
@@ -31,4 +33,11 @@ public class NetworkUtilityTest {
     final InetSocketAddress ipv6 = new InetSocketAddress("1:2:3:4:5:6:7:8", 80);
     assertThat(NetworkUtility.urlForSocketAddress("http", ipv6)).contains("[1:2:3:4:5:6:7:8]");
   }
+
+  @Test
+  public void assertPortIsNotAvailable() throws IOException {
+    final ServerSocket serverSocket = new ServerSocket(8541);
+    assertThat(!NetworkUtility.isPortAvailable(8541)).isEqualTo(true);
+    serverSocket.close();
+  }
 }