1 files changed, 148 insertions, 0 deletions
diff --git a/src/main/java/com/it_jaros/network_scanner/Scanner.java b/src/main/java/com/it_jaros/network_scanner/Scanner.java
new file mode 100644
index 0000000..81cbe1b
--- /dev/null
+++ b/src/main/java/com/it_jaros/network_scanner/Scanner.java
@@ -0,0 +1,148 @@
+package com.it_jaros.network_scanner;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.SocketException;
+import java.net.SocketTimeoutException;
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.LockSupport;
+
+public class Scanner {
+
+    private final Counter counter = new Counter();
+    private final ProgressBar progressBar = new ProgressBar();
+    private final Semaphore socketLimit;
+    private final int timeoutInMillis;
+    private final long delayInNanos;
+    private final int maxWorkersPerHost;
+
+    public Scanner(int socketLimit, int timeoutInMillis, int delayInMillis, int maxWorkersPerHost) {
+        this.timeoutInMillis = timeoutInMillis;
+        this.delayInNanos = TimeUnit.MILLISECONDS.toNanos(Math.max(0, delayInMillis));
+        this.socketLimit = new Semaphore(socketLimit);
+        this.maxWorkersPerHost = maxWorkersPerHost;
+    }
+
+    public List<ScanResult> scan(ScanOptions target) {
+        return scanTargets(target.targets(), target.ports());
+    }
+
+    public List<ScanResult> scanTargets(List<String> targets, String ports) {
+        List<ScanResult> results = new ArrayList<>();
+        progressBar.start();
+        try (ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor()) {
+            List<Future<ScanResult>> futures = new ArrayList<>();
+            for (String target : targets) {
+                futures.add(executor.submit(() -> scanTarget(target, ports)));
+            }
+
+            futures.forEach((Future<ScanResult> f) -> {
+                try {
+                    results.add(f.get());
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                } catch (ExecutionException e) {
+                    System.out.printf("%s -> %s%n", e.getClass().getSimpleName(), e.getMessage());
+                }
+            });
+        }
+
+        progressBar.stop();
+        System.out.println("Peak concurrent connects: " + counter.max());
+        return results;
+    }
+
+    private ScanResult scanTarget(String target, String ports) {
+        PortRange portRange = new PortRange(ports);
+        AtomicLong portSlotFactory = new AtomicLong(System.nanoTime());
+        Semaphore maxWorkers = new Semaphore(maxWorkersPerHost);
+        BitSet openPorts = new BitSet(PortRange.MAX_PORT);
+
+        Progress progress = new Progress(target, portRange.getTotal(), new AtomicInteger(), new AtomicInteger());
+        progressBar.submit(progress);
+
+        try (ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor()) {
+            List<Future<Integer>> futures = new ArrayList<>();
+            while (portRange.hasNext()) {
+                maxWorkers.acquireUninterruptibly();
+                final int currentPort = portRange.next();
+                futures.add(executor.submit(() -> {
+                    try {
+                        waitForSlot(portSlotFactory);
+                        int port = scanPort(target, currentPort);
+                        if (port != -1) {
+                            progress.open().incrementAndGet();
+                        }
+                        return port;
+                    } finally {
+                        maxWorkers.release();
+                        progress.done().incrementAndGet();
+                    }
+                }));
+            }
+
+            List<Throwable> errors = new ArrayList<>();
+            for (Future<Integer> f : futures) {
+                try {
+                    int port = f.get();
+                    if (port != -1) {
+                        // openPorts is not threadsafe, so we do not update it outside the worker threads
+                        openPorts.set(port);
+                    }
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                } catch (ExecutionException e) {
+                    errors.add(e);
+                }
+            }
+
+            if (!errors.isEmpty()) {
+                System.out.printf("Errors happened during scan of target %s%nErrors:%s -> %s", target, errors.size(), errors);
+            }
+        }
+
+        return new ScanResult(target, openPorts);
+    }
+
+    private int scanPort(String target, final int currentPort) {
+        return isTargetPortOpen(target, currentPort) ? currentPort : -1;
+    }
+
+    private void waitForSlot(AtomicLong scanSlotFactory) {
+        if (delayInNanos > 0) {
+            long slot = scanSlotFactory.getAndAdd(delayInNanos);
+            long wait = slot - System.nanoTime();
+            if (wait > 0)
+                LockSupport.parkNanos(wait);
+        }
+    }
+
+    private boolean isTargetPortOpen(String target, int port) {
+        socketLimit.acquireUninterruptibly();
+        counter.inc();
+        try (Socket socket = new Socket()) {
+            socket.connect(new InetSocketAddress(target, port), timeoutInMillis);
+            return true;
+        } catch (SocketException | SocketTimeoutException ignored) {
+            // Will happen a lot when scanning for open ports, so not needed
+        } catch (IOException e) {
+            System.out.printf("%s -> %s", e.getClass().getSimpleName(), e.getMessage());
+        } finally {
+            counter.dec();
+            socketLimit.release();
+        }
+
+        return false;
+    }
+}