PR: BAEL-6608 (#17781)

* PR: BAEL-6608

This PR aims to add a test class SubnetScannerUnitTest to this module.

* Update pom.xml

* Update SubnetScannerUnitTest.java

* Update SubnetScannerUnitTest.java

* Update pom.xml

Author: BenHelmyBen

core-java-modules/core-java-networking-5/pom.xml

@@ -36,6 +36,11 @@
             <artifactId>jsoup</artifactId>
             <version>${jsoup.version}</version>
         </dependency>
+        <dependency>
+            <groupId>commons-net</groupId>
+            <artifactId>commons-net</artifactId>
+            <version>${net.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpclient</artifactId>
@@ -67,11 +72,12 @@
     <properties>
         <commons-validator.version>1.7</commons-validator.version>
         <jsoup.version>1.17.2</jsoup.version>
+        <net.version>3.8.0</net.version>
         <httpclient.version>4.5.2</httpclient.version>
         <javax.ws.rs-api.version>2.1.1</javax.ws.rs-api.version>
         <jersey-common.version>2.22.2</jersey-common.version>
         <spring-web.version>6.0.6</spring-web.version>
         <jakarta.mail.version>2.0.1</jakarta.mail.version>
     </properties>
 
-</project>
+</project>

core-java-modules/core-java-networking-5/src/test/java/com/baeldung/ipaddresses/SubnetScannerUnitTest.java

@@ -0,0 +1,85 @@
+package com.baeldung.ipaddresses;
+
+import org.apache.commons.net.telnet.TelnetClient;
+import org.apache.commons.net.util.SubnetUtils;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.IntStream;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+public class SubnetScannerUnitTest {
+
+    @Test
+    public void givenSubnet_whenScanningForDevices_thenReturnConnectedIPs() throws Exception {
+        String subnet = getSubnet();
+        List<String> connectedIPs = new ArrayList<>();
+
+        for (int i = 1; i <= 254; i++) {
+            String ip = subnet + "." + i;
+            if (InetAddress.getByName(ip).isReachable(100)) {
+                connectedIPs.add(ip);
+            }
+        }
+
+        assertFalse(connectedIPs.isEmpty());
+    }
+
+    @Test
+    public void givenSubnet_whenUsingStream_thenReturnConnectedIPs() throws UnknownHostException {
+        String subnet = getSubnet();
+
+        List<String> connectedIPs = IntStream.rangeClosed(1, 254)
+                .mapToObj(i -> subnet + "." + i)
+                .filter(ip -> {
+                    try {
+                        return InetAddress.getByName(ip).isReachable(100);
+                    } catch (Exception e) {
+                        return false;
+                    }
+                })
+                .toList();
+
+        assertFalse(connectedIPs.isEmpty());
+    }
+
+    @Test
+    public void givenSubnet_whenCheckingForOpenPorts_thenReturnDevicesWithOpenPort() throws UnknownHostException {
+        SubnetUtils utils = new SubnetUtils(getSubnet() + ".0/24");
+        int port = 80;
+        List<String> devicesWithOpenPort = Arrays.stream(utils.getInfo().getAllAddresses())
+                .filter(ip -> {
+                    TelnetClient telnetClient = new TelnetClient();
+                    try {
+                        telnetClient.setConnectTimeout(100);
+                        telnetClient.connect(ip, port);
+                        return telnetClient.isConnected();
+                    } catch (Exception e) {
+                        return false;
+                    } finally {
+                        try {
+                            if (telnetClient.isConnected()) {
+                                telnetClient.disconnect();
+                            }
+                        } catch (IOException ex) {
+                            System.err.println(ex.getMessage());
+                        }
+                    }
+                })
+                .toList();
+
+        assertFalse(devicesWithOpenPort.isEmpty());
+    }
+
+    private String getSubnet() throws UnknownHostException {
+        InetAddress localHost = InetAddress.getLocalHost();
+        byte[] ipAddr = localHost.getAddress();
+        return String.format("%d.%d.%d", (ipAddr[0] & 0xFF), (ipAddr[1] & 0xFF), (ipAddr[2] & 0xFF));
+    }
+}